2622:. There is an appealing intuitive interpretation of this relationship in a radar. Matched filtering allows the entire energy received from a target to be compressed into a single bin (be it a range, Doppler, elevation, or azimuth bin). On the surface it appears that then within a fixed interval of time, perfect, error free, detection could be obtained. This is done by compressing all energy into an infinitesimal time slice. What limits this approach in the real world is that, while time is arbitrarily divisible, current is not. The quantum of electrical energy is an electron, and so the best that can be done is to match filter all energy into a single electron. Since the electron is moving at a certain temperature (
446:
50:
872:
763:
3423:
4122:, require liquid coolant. The electron beam must contain 5 to 10 times more power than the microwave output, which can produce enough heat to generate plasma. This plasma flows from the collector toward the cathode. The same magnetic focusing that guides the electron beam forces the plasma into the path of the electron beam but flowing in the opposite direction. This introduces FM modulation which degrades Doppler performance. To prevent this, liquid coolant with minimum pressure and flow rate is required, and deionized water is normally used in most high power surface radar systems that use Doppler processing.
3525:
2778:(PPI) radar with a rotating antenna, this will usually be seen as a "sun" or "sunburst" in the center of the display as the receiver responds to echoes from dust particles and misguided RF in the waveguide. Adjusting the timing between when the transmitter sends a pulse and when the receiver stage is enabled will generally reduce the sunburst without affecting the accuracy of the range since most sunburst is caused by a diffused transmit pulse reflected before it leaves the antenna. Clutter is considered a passive interference source since it only appears in response to radar signals sent by the radar.
672:
34:
2978:
detect. This could be offset by using more pulses, but this would shorten the maximum range. So each radar uses a particular type of signal. Long-range radars tend to use long pulses with long delays between them, and short range radars use smaller pulses with less time between them. As electronics have improved many radars now can change their pulse repetition frequency, thereby changing their range. The newest radars fire two pulses during one cell, one for short range (about 10 km (6.2 mi)) and a separate signal for longer ranges (about 100 km (62 mi)).
2838:(AGC), is a method that relies on clutter returns far outnumbering echoes from targets of interest. The receiver's gain is automatically adjusted to maintain a constant level of overall visible clutter. While this does not help detect targets masked by stronger surrounding clutter, it does help to distinguish strong target sources. In the past, radar AGC was electronically controlled and affected the gain of the entire radar receiver. As radars evolved, AGC became computer-software-controlled and affected the gain with greater granularity in specific detection cells.
2693:
1603:
3494:
target location in three dimensions. Most 2D surveillance radars use a spoiled parabolic antenna with a narrow azimuthal beamwidth and wide vertical beamwidth. This beam configuration allows the radar operator to detect an aircraft at a specific azimuth but at an indeterminate height. Conversely, so-called "nodder" height finding radars use a dish with a narrow vertical beamwidth and wide azimuthal beamwidth to detect an aircraft at a specific height but with low azimuthal precision.
3210:" capability required to improve military air combat survivability. Pulse-Doppler is also used for ground based surveillance radar required to defend personnel and vehicles. Pulse-doppler signal processing increases the maximum detection distance using less radiation close to aircraft pilots, shipboard personnel, infantry, and artillery. Reflections from terrain, water, and weather produce signals much larger than aircraft and missiles, which allows fast moving vehicles to hide using
3548:
2974:, accurate distance measurement requires high-speed electronics. In most cases, the receiver does not detect the return while the signal is being transmitted. Through the use of a duplexer, the radar switches between transmitting and receiving at a predetermined rate. A similar effect imposes a maximum range as well. In order to maximize range, longer times between pulses should be used, referred to as a pulse repetition time, or its reciprocal, pulse repetition frequency.
3165:
2998:
3012:
broadcasting at the time the reflected signal arrives back at the radar. By comparing the frequency of the two signals the difference can be easily measured. This is easily accomplished with very high accuracy even in 1940s electronics. A further advantage is that the radar can operate effectively at relatively low frequencies. This was important in the early development of this type when high-frequency signal generation was difficult or expensive.
3342:
2289:
623:
4291:
991:
657:
instead of broadcasting and receiving from an aimed antenna, CH broadcast a signal floodlighting the entire area in front of it, and then used one of Watson-Watt's own radio direction finders to determine the direction of the returned echoes. This fact meant CH transmitters had to be much more powerful and have better antennas than competing systems but allowed its rapid introduction using existing technologies.
575:
2857:). This clutter type is especially bothersome since it appears to move and behave like other normal (point) targets of interest. In a typical scenario, an aircraft echo is reflected from the ground below, appearing to the receiver as an identical target below the correct one. The radar may try to unify the targets, reporting the target at an incorrect height, or eliminating it on the basis of
5857:
2955:
3084:
kilowatts. On reception, the signal is sent into a system that delays different frequencies by different times. The resulting output is a much shorter pulse that is suitable for accurate distance measurement, while also compressing the received energy into a much higher energy peak and thus reducing the signal-to-noise ratio. The technique is largely universal on modern large radars.
4010:, subdivided as below. Oxygen in the air is an extremely effective attenuator around 60 GHz, as are other molecules at other frequencies, leading to the so-called propagation window at 94 GHz. Even in this window the attenuation is higher than that due to water at 22.2 GHz. This makes these frequencies generally useful only for short-range highly specific radars, like
3461:
4305:
611:
960:, are too strongly attenuated. Weather phenomena, such as fog, clouds, rain, falling snow, and sleet, that block visible light are usually transparent to radio waves. Certain radio frequencies that are absorbed or scattered by water vapour, raindrops, or atmospheric gases (especially oxygen) are avoided when designing radars, except when their detection is intended.
2970:: transmit a short pulse of radio signal (electromagnetic radiation) and measure the time it takes for the reflection to return. The distance is one-half the round trip time multiplied by the speed of the signal. The factor of one-half comes from the fact that the signal has to travel to the object and back again. Since radio waves travel at the
2684:(SNR). SNR is defined as the ratio of the signal power to the noise power within the desired signal; it compares the level of a desired target signal to the level of background noise (atmospheric noise and noise generated within the receiver). The higher a system's SNR the better it is at discriminating actual targets from noise signals.
3693:'s effective aperture figure means that for any given antenna (or reflector) size will be more efficient at longer wavelengths. Additionally, shorter wavelengths may interact with molecules or raindrops in the air, scattering the signal. Very long wavelengths also have additional diffraction effects that make them suitable for
3123:, military radar). The Doppler effect is only able to determine the relative speed of the target along the line of sight from the radar to the target. Any component of target velocity perpendicular to the line of sight cannot be determined by using the Doppler effect alone, but it can be determined by tracking the target's
3203:. Coherency requirements are not as strict as those for military systems because individual signals ordinarily do not need to be separated. Less sophisticated filtering is required, and range ambiguity processing is not normally needed with weather radar in comparison with military radar intended to track air vehicles.
3538:
Applied similarly to the parabolic reflector, the slotted waveguide is moved mechanically to scan and is particularly suitable for non-tracking surface scan systems, where the vertical pattern may remain constant. Owing to its lower cost and less wind exposure, shipboard, airport surface, and harbour
2885:
Jamming is problematic to radar since the jamming signal only needs to travel one way (from the jammer to the radar receiver) whereas the radar echoes travel two ways (radar-target-radar) and are therefore significantly reduced in power by the time they return to the radar receiver in accordance with
2862:
certain height. Monopulse can be improved by altering the elevation algorithm used at low elevation. In newer air traffic control radar equipment, algorithms are used to identify the false targets by comparing the current pulse returns to those adjacent, as well as calculating return improbabilities.
845:
to monitor vehicle speeds on the roads. Automotive radars are used for adaptive cruise control and emergency breaking on vehicles by ignoring stationary roadside objects that could cause incorrect brake application and instead measuring moving objects to prevent collision with other vehicles. As part
656:
Given all required funding and development support, the team produced working radar systems in 1935 and began deployment. By 1936, the first five Chain Home (CH) systems were operational and by 1940 stretched across the entire UK including
Northern Ireland. Even by standards of the era, CH was crude;
3571:
Phased array antennas are composed of evenly spaced similar antenna elements, such as aerials or rows of slotted waveguide. Each antenna element or group of antenna elements incorporates a discrete phase shift that produces a phase gradient across the array. For example, array elements producing a 5
3190:
to produce the display showing different frequencies. Each different distance produces a different spectrum. These spectra are used to perform the detection process. This is required to achieve acceptable performance in hostile environments involving weather, terrain, and electronic countermeasures.
3074:
The two techniques outlined above both have their disadvantages. The pulse timing technique has an inherent tradeoff in that the accuracy of the distance measurement is inversely related to the length of the pulse, while the energy, and thus direction range, is directly related. Increasing power for
3039:
riding on the receive signal is proportional to the time delay between the radar and the reflector. The frequency shift becomes greater with greater time delay. The frequency shift is directly proportional to the distance travelled. That distance can be displayed on an instrument, and it may also be
2977:
These two effects tend to be at odds with each other, and it is not easy to combine both good short range and good long range in a single radar. This is because the short pulses needed for a good minimum range broadcast have less total energy, making the returns much smaller and the target harder to
2585:
Noise is also generated by external sources, most importantly the natural thermal radiation of the background surrounding the target of interest. In modern radar systems, the internal noise is typically about equal to or lower than the external noise. An exception is if the radar is aimed upwards at
3059:
Terrestrial radar uses low-power FM signals that cover a larger frequency range. The multiple reflections are analyzed mathematically for pattern changes with multiple passes creating a computerized synthetic image. Doppler effects are used which allows slow moving objects to be detected as well as
3011:
Another form of distance measuring radar is based on frequency modulation. In these systems, the frequency of the transmitted signal is changed over time. Since the signal takes a finite time to travel to and from the target, the received signal is a different frequency than what the transmitter is
2861:
or a physical impossibility. Terrain bounce jamming exploits this response by amplifying the radar signal and directing it downward. These problems can be overcome by incorporating a ground map of the radar's surroundings and eliminating all echoes which appear to originate below ground or above a
2781:
Clutter is detected and neutralized in several ways. Clutter tends to appear static between radar scans; on subsequent scan echoes, desirable targets will appear to move, and all stationary echoes can be eliminated. Sea clutter can be reduced by using horizontal polarization, while rain is reduced
3227:
processing is required to identify the true range of all reflected signals. Radial movement is usually linked with
Doppler frequency to produce a lock signal that cannot be produced by radar jamming signals. Pulse-Doppler signal processing also produces audible signals that can be used for threat
3218:
to avoid detection until an attack vehicle is too close to destroy. Pulse-Doppler signal processing incorporates more sophisticated electronic filtering that safely eliminates this kind of weakness. This requires the use of medium pulse-repetition frequency with phase coherent hardware that has a
345:
was the first to use radio waves to detect "the presence of distant metallic objects". In 1904, he demonstrated the feasibility of detecting a ship in dense fog, but not its distance from the transmitter. He obtained a patent for his detection device in April 1904 and later a patent for a related
3608:
As the price of electronics has fallen, phased array radars have become more common. Almost all modern military radar systems are based on phased arrays, where the small additional cost is offset by the improved reliability of a system with no moving parts. Traditional moving-antenna designs are
770:
The information provided by radar includes the bearing and range (and therefore position) of the object from the radar scanner. It is thus used in many different fields where the need for such positioning is crucial. The first use of radar was for military purposes: to locate air, ground and sea
3493:
weather radar uses a symmetric antenna to perform detailed volumetric scans of the atmosphere. Spoiled parabolic antennas produce a narrow beam in one dimension and a relatively wide beam in the other. This feature is useful if target detection over a wide range of angles is more important than
1073:
consists of three flat surfaces meeting like the inside corner of a cube. The structure will reflect waves entering its opening directly back to the source. They are commonly used as radar reflectors to make otherwise difficult-to-detect objects easier to detect. Corner reflectors on boats, for
3688:
Opposing the move to smaller wavelengths are a number of practical issues. For one, the electronics needed to produce high power very short wavelengths were generally more complex and expensive than the electronics needed for longer wavelengths or didn't exist at all. Another issue is that the
3198:
to measure radial wind velocity and precipitation rate in each different volume of air. This is linked with computing systems to produce a real-time electronic weather map. Aircraft safety depends upon continuous access to accurate weather radar information that is used to prevent injuries and
3079:
often operating in the tens of megawatts. The continuous wave methods spread this energy out in time and thus require much lower peak power compared to pulse techniques, but requires some method of allowing the sent and received signals to operate at the same time, often demanding two separate
790:
screens by operators who thereby give radio landing instructions to the pilot, maintaining the aircraft on a defined approach path to the runway. Military fighter aircraft are usually fitted with air-to-air targeting radars, to detect and target enemy aircraft. In addition, larger specialized
405:
discovered that ships passing through the beam path caused the received signal to fade in and out. Taylor submitted a report, suggesting that this phenomenon might be used to detect the presence of ships in low visibility, but the Navy did not immediately continue the work. Eight years later,
3083:
The introduction of new electronics in the 1960s allowed the two techniques to be combined. It starts with a longer pulse that is also frequency modulated. Spreading the broadcast energy out in time means lower peak energies can be used, with modern examples typically on the order of tens of
590:
and turned the request over to
Wilkins. Wilkins returned a set of calculations demonstrating the system was basically impossible. When Watson-Watt then asked what such a system might do, Wilkins recalled the earlier report about aircraft causing radio interference. This revelation led to the
3572:
degree phase shift for each wavelength across the array face will produce a beam pointed 5 degrees away from the centerline perpendicular to the array face. Signals travelling along that beam will be reinforced. Signals offset from that beam will be cancelled. The amount of reinforcement is
2229:
As an example, a
Doppler weather radar with a pulse rate of 2 kHz and transmit frequency of 1 GHz can reliably measure weather speed up to at most 150 m/s (340 mph), thus cannot reliably determine radial velocity of aircraft moving 1,000 m/s (2,200 mph).
513:, produced an experimental apparatus, RAPID, capable of detecting an aircraft within 3 km of a receiver. The Soviets produced their first mass production radars RUS-1 and RUS-2 Redut in 1939 but further development was slowed following the arrest of Oshchepkov and his subsequent
3657:, such multiple aperture arrays, when used in transmitters, result in narrow beams at the expense of reducing the total power transmitted to the target. In principle, such techniques could increase spatial resolution, but the lower power means that this is generally not effective.
3134:(CW radar), by sending out a very pure signal of a known frequency. CW radar is ideal for determining the radial component of a target's velocity. CW radar is typically used by traffic enforcement to measure vehicle speed quickly and accurately where the range is not important.
3685:. This provides a strong incentive to use shorter wavelengths as this will result in smaller antennas. Shorter wavelengths also result in higher resolution due to diffraction, meaning the shaped reflector seen on most radars can also be made smaller for any desired beamwidth.
2573:
amplification. Another reason for heterodyne processing is that for fixed fractional bandwidth, the instantaneous bandwidth increases linearly in frequency. This allows improved range resolution. The one notable exception to heterodyne (downconversion) radar systems is
3781:
Very long range, ground penetrating; 'very high frequency'. Early radar systems generally operated in VHF as suitable electronics had already been developed for broadcast radio. Today this band is heavily congested and no longer suitable for radar due to interference.
2881:
tactic, or unintentional, as with friendly forces operating equipment that transmits using the same frequency range. Jamming is considered an active interference source, since it is initiated by elements outside the radar and in general unrelated to the radar signals.
414:(NRL) observed similar fading effects from passing aircraft; this revelation led to a patent application as well as a proposal for further intensive research on radio-echo signals from moving targets to take place at NRL, where Taylor and Young were based at the time.
2679:
Radar systems must overcome unwanted signals in order to focus on the targets of interest. These unwanted signals may originate from internal and external sources, both passive and active. The ability of the radar system to overcome these unwanted signals defines its
2989:, reflect off a target, and return to the radar antenna. Since a nautical mile is defined as 1,852 m, then dividing this distance by the speed of light (299,792,458 m/s), and then multiplying the result by 2 yields a result of 12.36 μs in duration.
3914:
radar; short-range tracking. Named X band because the frequency was a secret during WW2. Diffraction off raindrops during heavy rain limits the range in the detection role and makes this suitable only for short-range roles or those that deliberately detect rain.
3293:
Historical information is accumulated and used to predict future position for use with air traffic control, threat estimation, combat system doctrine, gun aiming, and missile guidance. Position data is accumulated by radar sensors over the span of a few minutes.
778:, aircraft can be equipped with radar devices that warn of aircraft or other obstacles in or approaching their path, display weather information, and give accurate altitude readings. The first commercial device fitted to aircraft was a 1938 Bell Lab unit on some
3595:. The massive redundancy associated with having a large number of array elements increases reliability at the expense of gradual performance degradation that occurs as individual phase elements fail. To a lesser extent, Phased array radars have been used in
1049:
Radar waves scatter in a variety of ways depending on the size (wavelength) of the radio wave and the shape of the target. If the wavelength is much shorter than the target's size, the wave will bounce off in a way similar to the way light is reflected by a
350:. It operated on a 50 cm wavelength and the pulsed radar signal was created via a spark-gap. His system already used the classic antenna setup of horn antenna with parabolic reflector and was presented to German military officials in practical tests in
1074:
example, make them more detectable to avoid collision or during a rescue. For similar reasons, objects intended to avoid detection will not have inside corners or surfaces and edges perpendicular to likely detection directions, which leads to "odd" looking
797:
are used to measure the bearing and distance of ships to prevent collision with other ships, to navigate, and to fix their position at sea when within range of shore or other fixed references such as islands, buoys, and lightships. In port or in harbour,
3095:
is the change in distance to an object with respect to time. Thus the existing system for measuring distance, combined with a memory capacity to see where the target last was, is enough to measure speed. At one time the memory consisted of a user making
2462:
1054:. If the wavelength is much longer than the size of the target, the target may not be visible because of poor reflection. Low-frequency radar technology is dependent on resonances for detection, but not identification, of targets. This is described by
3442:
for reception, each on a different display. The maximum return would be detected with an antenna at right angles to the target, and a minimum with the antenna pointed directly at it (end on). The operator could determine the direction to a target by
3430:
Radio signals broadcast from a single antenna will spread out in all directions, and likewise a single antenna will receive signals equally from all directions. This leaves the radar with the problem of deciding where the target object is located.
706:
had an article in which a U.S. scientist speculated about the
British early warning system on the English east coast and came close to what it was and how it worked. Watson-Watt was sent to the U.S. in 1941 to advise on air defense after Japan's
525:
dive bombers. More than 230 Gneiss-2 stations were produced by the end of 1944. The French and Soviet systems, however, featured continuous-wave operation that did not provide the full performance ultimately synonymous with modern radar systems.
3866:
Moderate range surveillance, Terminal air traffic control, long-range weather, marine radar; 'S' for 'sentimetric', its code-name during WWII. Less efficient than L, but offering higher resolution, making them especially suitable for long-range
1638:
rely on the
Doppler effect to enhance performance. This produces information about target velocity during the detection process. This also allows small objects to be detected in an environment containing much larger nearby slow moving objects.
850:, fixed-position stopped vehicle detection (SVD) radars are mounted on the roadside to detect stranded vehicles, obstructions and debris by inverting the automotive radar approach and ignoring moving objects. Smaller radar systems are used to
3137:
When using a pulsed radar, the variation between the phase of successive returns gives the distance the target has moved between pulses, and thus its speed can be calculated. Other mathematical developments in radar signal processing include
1062:. Early radars used very long wavelengths that were larger than the targets and thus received a vague signal, whereas many modern systems use shorter wavelengths (a few centimetres or less) that can image objects as small as a loaf of bread.
553:
3447:
the antenna so one display showed a maximum while the other showed a minimum. One serious limitation with this type of solution is that the broadcast is sent out in all directions, so the amount of energy in the direction being examined is
3289:
A Track algorithm is a radar performance enhancement strategy. Tracking algorithms provide the ability to predict future position of multiple moving objects based on the history of the individual positions being reported by sensor systems.
5216:
But by 1940, it was the
British who had made a spectacular breakthrough: the resonant cavity magnetron, a radar transmitter far more powerful than its predecessors.... The magnetron stunned the Americans. Their research was years off the
4577:
3185:
Pulse-Doppler signal processing includes frequency filtering in the detection process. The space between each transmit pulse is divided into range cells or range gates. Each cell is filtered independently much like the process used by a
1238:
1911:
Only the radial component of the velocity is relevant. When the reflector is moving at right angle to the radar beam, it has no relative velocity. Objects moving parallel to the radar beam produce the maximum
Doppler frequency shift.
2913:
and cannot fully be eliminated when directly facing a jammer which uses the same frequency and polarization as the radar. Sidelobe jamming can be overcome by reducing receiving sidelobes in the radar antenna design and by using an
2252:
of the wave. For a transmitted radar signal, the polarization can be controlled to yield different effects. Radars use horizontal, vertical, linear, and circular polarization to detect different types of reflections. For example,
5186:
It not only changed the course of the war by allowing us to develop airborne radar systems, it remains the key piece of technology that lies at the heart of your microwave oven today. The cavity magnetron's invention changed the
481:, and the United States, independently and in great secrecy, developed technologies that led to the modern version of radar. Australia, Canada, New Zealand, and South Africa followed prewar Great Britain's radar development, and
3318:
Radar video returns from aircraft can be subjected to a plot extraction process whereby spurious and interfering signals are discarded. A sequence of target returns can be monitored through a device known as a plot extractor.
1614:
Frequency shift is caused by motion that changes the number of wavelengths between the reflector and the radar. This can degrade or enhance radar performance depending upon how it affects the detection process. As an example,
1642:
Doppler shift depends upon whether the radar configuration is active or passive. Active radar transmits a signal that is reflected back to the receiver. Passive radar depends upon the object sending a signal to the receiver.
3989:
Mapping, short range, airport surveillance; frequency just above K band (hence 'a') Photo radar, used to trigger cameras which take pictures of license plates of cars running red lights, operates at 34.300 ± 0.100 GHz.
1557:
2710:
Clutter refers to radio frequency (RF) echoes returned from targets which are uninteresting to radar operators. Such targets include man-made objects such as buildings and — intentionally — by radar countermeasures such as
3027:
or sawtooth pattern at audio frequencies. The signal is then sent out from one antenna and received on another, typically located on the bottom of the aircraft, and the signal can be continuously compared using a simple
365:
used radio technology to provide advance warning of thunderstorms to airmen and during the 1920s went on to lead the U.K. research establishment to make many advances using radio techniques, including the probing of the
3322:
The non-relevant real time returns can be removed from the displayed information and a single plot displayed. In some radar systems, or alternatively in the command and control system to which the radar is connected, a
2554:
Noise typically appears as random variations superimposed on the desired echo signal received in the radar receiver. The lower the power of the desired signal, the more difficult it is to discern it from the noise. The
1822:
2224:
3176:
axis represents each successive transmit pulse interval during which samples are taken. The Fast
Fourier Transform process converts time-domain samples into frequency domain spectra. This is sometimes called the
2876:
Radar jamming refers to radio frequency signals originating from sources outside the radar, transmitting in the radar's frequency and thereby masking targets of interest. Jamming may be intentional, as with an
6455:
3485:
Parabolic reflectors can be either symmetric parabolas or spoiled parabolas: Symmetric parabolic antennas produce a narrow "pencil" beam in both the X and Y dimensions and consequently have a higher gain. The
4143:
and formation of highly flammable alcohol. The loss of a U.S. Navy aircraft in 1978 was attributed to a silicate ester fire. Coolanol is also expensive and toxic. The U.S. Navy has instituted a program named
1905:
154:
to determine properties of the objects. Radio waves (pulsed or continuous) from the transmitter reflect off the objects and return to the receiver, giving information about the objects' locations and speeds.
5981:, National Imagery and Mapping Agency, Bethesda, MD 2001 (US govt publication '...intended to be used primarily as a manual of instruction in navigation schools and by naval and merchant marine personnel.')
3969:
on either side used instead for surveillance. K-band is used for detecting clouds by meteorologists, and by police for detecting speeding motorists. K-band radar guns operate at 24.150 ± 0.100 GHz.
947:
The weak absorption of radio waves by the medium through which they pass is what enables radar sets to detect objects at relatively long ranges—ranges at which other electromagnetic wavelengths, such as
2508:
Radar sensitivity and the power of the return signal as computed in the radar equation. This component includes factors such as the environmental conditions and the size (or radar cross section) of the
936:
Radar receivers are usually, but not always, in the same location as the transmitter. The reflected radar signals captured by the receiving antenna are usually very weak. They can be strengthened by
3478:"dish" to create a tight broadcast beam, typically using the same dish as the receiver. Such systems often combine two radar frequencies in the same antenna in order to allow automatic steering, or
4581:
2824:
that subtracts the received signal from two successive pulses using phase to reduce signals from slow-moving objects. This can be adapted for systems that lack a coherent transmitter, such as
1326:
3602:. As of 2017, NOAA plans to implement a national network of Multi-Function Phased array radars throughout the United States within 10 years, for meteorological studies and flight monitoring.
649:; without it, significant numbers of fighter aircraft, which Great Britain did not have available, would always have needed to be in the air to respond quickly. The radar formed part of the "
4018:
or use in space where attenuation is not a problem. Multiple letters are assigned to these bands by different groups. These are from
Baytron, a now defunct company that made test equipment.
5630:
2629:
Noise is random and target signals are not. Signal processing can take advantage of this phenomenon to reduce the noise floor using two strategies. The kind of signal integration used with
3700:
The traditional band names originated as code-names during World War II and are still in military and aviation use throughout the world. They have been adopted in the United States by the
2112:
645:" along the East and South coasts of England in time for the outbreak of World War II in 1939. This system provided the vital advance information that helped the Royal Air Force win the
1065:
Short radio waves reflect from curves and corners in a way similar to glint from a rounded piece of glass. The most reflective targets for short wavelengths have 90° angles between the
496:(CSF) headed by Maurice Ponte with Henri Gutton, Sylvain Berline and M. Hugon, began developing an obstacle-locating radio apparatus, aspects of which were installed on the ocean liner
2820:, so individual signals can be separated from multiple reflectors located in the same volume using velocity differences. This requires a coherent transmitter. Another technique uses a
5309:
3107:
If the transmitter's output is coherent (phase synchronized), there is another effect that can be used to make almost instant speed measurements (no memory is required), known as the
607:, was very impressed with their system's potential and funds were immediately provided for further operational development. Watson-Watt's team patented the device in patent GB593017.
425:
test unit, operating at 50 cm (600 MHz) and using pulsed modulation which gave successful laboratory results. In January 1931, a writeup on the apparatus was entered in the
287:
rather than radio waves. With the emergence of driverless vehicles, radar is expected to assist the automated platform to monitor its environment, thus preventing unwanted incidents.
1026:, or a significant change in atomic density between the object and what is surrounding it, will usually scatter radar (radio) waves from its surface. This is particularly true for
2296:
5413:
4703:
is actually an acronym that stands for RAdio Detection and Ranging. It was officially coined by U.S. Navy Lieutenant Commanders Samuel M. Tucker and F.R. Furth in November 1940
3506:
Secondary Scan: A scanning technique where the antenna feed is moved to produce a scanning beam, examples include conical scan, unidirectional sector scan, lobe switching, etc.
3509:
Palmer Scan: A scanning technique that produces a scanning beam by moving the main antenna and its feed. A Palmer Scan is a combination of a Primary Scan and a Secondary Scan.
4602:
McGraw-Hill dictionary of scientific and technical terms / Daniel N. Lapedes, editor in chief. Lapedes, Daniel N. New York; Montreal : McGraw-Hill, 1976. , 1634, A26 p.
338:
caused by the passage of a third vessel. In his report, Popov wrote that this phenomenon might be used for detecting objects, but he did nothing more with this observation.
2655:
3649:
techniques, using an array of separate dishes that are phased into a single effective aperture, are not typical for radar applications, although they are widely used in
3438:, with directional receiver antennas which were pointed in various directions. For instance, the first system to be deployed, Chain Home, used two straight antennas at
921:
possible in certain cases. The radar signals that are reflected back towards the radar receiver are the desirable ones that make radar detection work. If the object is
1352:
5805:
2142:
2048:
2021:
1994:
1967:
1940:
1725:
1698:
1671:
2565:
is produced by electrons in transit across a discontinuity, which occurs in all detectors. Shot noise is the dominant source in most receivers. There will also be
909:
in many directions, although some of them will be absorbed and penetrate into the target. Radar signals are reflected especially well by materials of considerable
429:
maintained by the Royal Engineers. This is the first official record in Great Britain of the technology that was used in coastal defence and was incorporated into
4800:
Verfahren zur Bestimmung der Entfernung von metallischen Gegenständen (Schiffen o. dgl.), deren Gegenwart durch das Verfahren nach Patent 16556 festgestellt wird.
3816:), ground penetrating, foliage penetrating; 'ultra high frequency'. Efficiently produced and received at very high energy levels, and also reduces the effects of
1111:
1086:, are very reflective but do not direct the scattered energy back toward the source. The extent to which an object reflects or scatters radio waves is called its
1562:
This shows that the received power declines as the fourth power of the range, which means that the received power from distant targets is relatively very small.
493:
3796:'P' for 'previous', applied retrospectively to early radar systems; essentially HF + VHF. Often used for remote sensing because of good vegetation penetration.
1745:
4068:
High voltage switch for non-coherent keyed power-oscillators These modulators consist of a high voltage pulse generator formed from a high voltage supply, a
4715:
4148:(P2) to eliminate or reduce the volume and toxicity of waste, air emissions, and effluent discharges. Because of this, Coolanol is used less often today.
7112:
687:
in the UK, which allowed the creation of relatively small systems with sub-meter resolution. Britain shared the technology with the U.S. during the 1940
972:
emitted by the target objects themselves, such as infrared radiation (heat). This process of directing artificial radio waves towards objects is called
4091:
waveform. This waveform can be generated by low power/low-voltage input signals. In this case the radar transmitter must be a power-amplifier, e.g., a
3503:
Primary Scan: A scanning technique where the main antenna aerial is moved to produce a scanning beam, examples include circular scan, sector scan, etc.
1447:
510:
599:
shortwave transmitter as the source and their GPO receiver setup in a field while a bomber flew around the site. When the plane was clearly detected,
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346:
amendment for estimating the distance to the ship. He also obtained a British patent on 23 September 1904 for a full radar system, that he called a
5637:
4816:
730:
The war precipitated research to find better resolution, more portability, and more features for radar, including small, lightweight sets to equip
6668:
3612:
Phased array radars are valued for use in aircraft since they can track multiple targets. The first aircraft to use a phased array radar was the
723:, Cambridge, Massachusetts which developed microwave radar technology in the years 1941–45. Later, in 1943, Page greatly improved radar with the
4683:
3194:
The primary purpose is to measure both the amplitude and frequency of the aggregate reflected signal from multiple distances. This is used with
6801:
1753:
5923:
4834:
3910:, weather, medium-resolution mapping and ground surveillance; in the United States the narrow range 10.525 GHz ±25 MHz is used for
390:
model after noting its manual's description of a "fading" effect (the common term for interference at the time) when aircraft flew overhead.
5969:
5811:. Melbourne, Australia: Aeronautical Research Laboratory, Defense Science and Technology Organisation, Department of Defense. Archived from
5317:
3583:), but electronic device limitations led to poor performance. Phased array radars were originally used for missile defence (see for example
2958:
Pulse radar: The round-trip time for the radar pulse to get to the target and return is measured. The distance is proportional to this time.
2543:
that affect range performance. Reflectors that are too far away produce too little signal to exceed the noise floor and cannot be detected.
2150:
5927:". Privateline.com. (Anecdotal account of the carriage of the world's first high power cavity magnetron from Britain to the US during WW2.)
3383:
that serves as a switch between the antenna and the transmitter or the receiver for the signal when the antenna is used in both situations.
633:
Development of radar greatly expanded on 1 September 1936, when Watson-Watt became superintendent of a new establishment under the British
6098:
The invention that changed the world: how a small group of radar pioneers won the Second World War and launched a technological revolution
2626:) this noise source cannot be further eroded. Ultimately, radar, like all macro-scale entities, is profoundly impacted by quantum theory.
2540:
2794:
791:
military aircraft carry powerful airborne radars to observe air traffic over a wide region and direct fighter aircraft towards targets.
5672:
5402:
5128:
2054:, since the returned frequency otherwise cannot be distinguished from shifting of a harmonic frequency above or below, thus requiring:
1842:
4183:
based on the comparison of reference signals with radio signals reflected, or retransmitted, from the position to be determined. Each
5690:
4898:
Hyland, L.A, A.H. Taylor, and L.C. Young; "System for detecting objects by radio," U.S. Patent No. 1981884, granted 27 November 1934
5865:
2817:
641:, near Felixstowe, Suffolk. Work there resulted in the design and installation of aircraft detection and tracking stations called "
7132:
7122:
6379:
5538:
3605:
Phased array antennas can be built to conform to specific shapes, like missiles, infantry support vehicles, ships, and aircraft.
529:
Full radar evolved as a pulsed system, and the first such elementary apparatus was demonstrated in December 1934 by the American
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5992:
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of that transmitted. To get a reasonable amount of power on the "target", the transmitting aerial should also be directional.
3023:. In these systems a "carrier" radar signal is frequency modulated in a predictable way, typically varying up and down with a
1576:= 1 is a simplification for transmission in a vacuum without interference. The propagation factor accounts for the effects of
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3708:. Most countries have additional regulations to control which parts of each band are available for civilian or military use.
3705:
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2825:
2498:
Line of sight, which depends on the height above the ground. Without a direct line of sight, the path of the beam is blocked.
1018:
from the first, the waves will reflect or scatter from the boundary between the materials. This means that a solid object in
720:
5388:
4731:"Performance Assessment of an Integrated Radar Architecture for Multi-Types Frontal Object Detection for Autonomous Vehicle"
6611:
5268:
4265:
3624:
3044:. This signal processing is similar to that used in speed detecting Doppler radar. Example systems using this approach are
2715:. Such targets also include natural objects such as ground, sea, and — when not being tasked for meteorological purposes —
2505:. The maximum non-ambiguous range is the distance the pulse can travel to and return from before the next pulse is emitted.
4929:
The Origins and Development of Radar in the Royal Navy, 1935–45 with Particular Reference to Decimetric Gunnery Equipments
4652:
3327:
is used to associate the sequence of plots belonging to individual targets and estimate the targets' headings and speeds.
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6661:
6630:
A set of 10 video lectures developed at Lincoln Laboratory to develop an understanding of radar systems and technologies.
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or a solid state transmitter. In this way, the transmitted pulse is intrapulse-modulated and the radar receiver must use
3631:
2919:
5269:"Scotland's little-known WWII hero who helped beat the Luftwaffe with invention of radar set to be immortalised in film"
2528:
Signal noise is an internal source of random variations in the signal, which is generated by all electronic components.
6525:
6465:
5430:
4545:
4216:
Radar come in a variety of configurations in the emitter, the receiver, the antenna, wavelength, scan strategies, etc.
4050:
Used as a visual sensor for experimental autonomous vehicles, high-resolution meteorological observation, and imaging.
2491:
sinks below the horizon. Furthermore, the signal is attenuated by the medium the beam crosses, and the beam disperses.
1282:
604:
6476:
2479:
A radar beam follows a linear path in vacuum but follows a somewhat curved path in atmosphere due to variation in the
7009:
6627:
6411:
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still widely used in roles where cost is a significant factor such as air traffic surveillance and similar systems.
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An electronic section that controls all those devices and the antenna to perform the radar scan ordered by software.
2890:. Jammers therefore can be much less powerful than their jammed radars and still effectively mask targets along the
5367:
2060:
1619:
can interact with Doppler to produce signal cancellation at certain radial velocities, which degrades performance.
1058:, an effect that creates Earth's blue sky and red sunsets. When the two length scales are comparable, there may be
3220:
3032:
modulator that produces an audio frequency tone from the returned signal and a portion of the transmitted signal.
1046:. This is the radio equivalent of painting something a dark colour so that it cannot be seen by the eye at night.
7102:
4204:
3248:
3159:
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2658:
2023:. As a result, the Doppler measurement is only non-ambiguous if the Doppler frequency shift is less than half of
1002:). The radar's frequency, pulse form, polarization, signal processing, and antenna determine what it can observe.
5760:
5080:
2559:
is a measure of the noise produced by a receiver compared to an ideal receiver, and this needs to be minimized.
700:
showed an example of a radar unit using the Watson-Watt patent in an article on air defence. Also, in late 1941
55:
Radar of the type used for detection of aircraft. It rotates steadily, sweeping the airspace with a narrow beam.
7097:
6654:
4382:
4145:
4080:, a special type of vacuum tube that converts DC (usually pulsed) into microwaves. This technology is known as
3868:
3681:
Antennas generally have to be sized similar to the wavelength of the operational frequency, normally within an
3256:
3200:
2248:, the electric field is perpendicular to the direction of propagation, and the electric field direction is the
445:
4909:
4787:
Patent DE165546; Verfahren, um metallische Gegenstände mittels elektrischer Wellen einem Beobachter zu melden.
7092:
7087:
2457:{\displaystyle H=\left({\sqrt {r^{2}+(k_{e}a_{e})^{2}+2rk_{e}a_{e}sin(\theta _{e})}}\right)-k_{e}a_{e}+h_{a}}
847:
3036:
2898:). Jammers have an added effect of affecting radars along other lines of sight through the radar receiver's
517:
sentence. In total, only 607 Redut stations were produced during the war. The first Russian airborne radar,
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by post-processing motion data from a single moving source, on the other hand, is widely used in space and
3252:
2531:
Reflected signals decline rapidly as distance increases, so noise introduces a radar range limitation. The
1030:
materials such as metal and carbon fibre, making radar well-suited to the detection of aircraft and ships.
884:
5934:
4084:. In this way, the transmitted pulse of RF radiation is kept to a defined and usually very short duration.
3515:: The radar beam is rotated in a small circle around the "boresight" axis, which is pointed at the target.
3390:. Knowing the shape of the desired received signal (a pulse), an optimal receiver can be designed using a
6885:
5742:
4995:
Frederick Seitz, Norman G. Einspruch, Electronic Genie: The Tangled History of Silicon – 1998 – page 104
3635:
3301:
2871:
1082:, especially at longer wavelengths. Half wavelength long wires or strips of conducting material, such as
858:
for computer interaction. Automatic door opening, light activation and intruder sensing are also common.
806:
743:
735:
489:
311:
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5004:
John Erickson. Radio-Location and the Air Defence Problem: The Design and Development of Soviet Radar.
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Satellite transponders; a compromise (hence 'C') between X and S bands; weather; long range tracking
3336:
3264:
3041:
2891:
2831:
2735:
trails. Radar clutter can also be caused by other atmospheric phenomena, such as disturbances in the
2245:
1566:
1007:
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534:
450:
411:
257:
245:
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3104:. Modern radar systems perform the equivalent operation faster and more accurately using computers.
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targets. This evolved in the civilian field into applications for aircraft, ships, and automobiles.
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272:
253:
6565:
Robert Calderbank; S. Howard; Bill Moran (2009). "Waveform diversity in radar signal processing".
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3139:
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2841:
Clutter may also originate from multipath echoes from valid targets caused by ground reflection,
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2636:
910:
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375:
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at long distances. Through his lightning experiments, Watson-Watt became an expert on the use of
120:
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Similarly, in the UK, L. S. Alder took out a secret provisional patent for Naval radar in 1928.
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4272:
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2487:. Even when the beam is emitted parallel to the ground, the beam rises above the ground as the
2283:
1083:
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210:
183:
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20:
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act to provide the waveform of the RF-pulse. There are two different radar modulator designs:
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342:
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174:, which allowed the creation of relatively small systems with sub-meter resolution. The term
40:
5676:
5136:
1233:{\displaystyle P_{r}={\frac {P_{t}G_{t}A_{r}\sigma F^{4}}{{(4\pi )}^{2}R_{t}^{2}R_{r}^{2}}}}
201:
The modern uses of radar are highly diverse, including air and terrestrial traffic control,
146:, a receiving antenna (often the same antenna is used for transmitting and receiving) and a
6574:
5945:
5836:
ITU Radio Regulations, Section IV. Radio Stations and Systems – Article 1.100, definition:
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1999:
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237:
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76:
3934:
High-resolution, also used for satellite transponders, frequency under K band (hence 'u')
2578:
radar. Here a single cycle, or transient wave, is used similar to UWB communications, see
968:
Radar relies on its own transmissions rather than light from the Sun or the Moon, or from
766:
Commercial marine radar antenna. The rotating antenna radiates a vertical fan-shaped beam.
8:
6826:
6786:
6704:
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5694:
5529:
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4735:
2018 IEEE International Conference on Automatic Control and Intelligent Systems (I2CACIS)
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to detect precipitation). Other methods attempt to increase the signal-to-clutter ratio.
2787:
2662:
2661:, which reduces the noise floor by the number of filters. These improvements depend upon
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1627:
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industries, have replaced the traditional military designations with their own systems.
3579:
Phased array radars have been in use since the earliest years of radar in World War II (
2261:
returns usually indicate metal surfaces. Random polarization returns usually indicate a
1580:
and shadowing and depends on the details of the environment. In a real-world situation,
7038:
6699:
6590:
6496:
6457:
Signal design for good correlation: for wireless communication, cryptography, and radar
6422:
6205:
Kaiser, Gerald, Chapter 10 in "A Friendly Guide to Wavelets", Birkhauser, Boston, 1994.
5514:
M. Castelaz. "Exploration: The Doppler Effect". Pisgah Astronomical Research Institute.
5345:
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92:
5636:. Syracuse Research Corporation; Massachusetts Institute of Technology. Archived from
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longer range while maintaining accuracy demands extremely high peak power, with 1960s
549:
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4709:
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which makes use of the change of frequency of returns from moving targets ("chirp").
3069:
2923:
2740:
2051:
1969:, the resulting frequency spectrum will contain harmonic frequencies above and below
957:
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702:
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542:
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335:
6594:
5114:
4798:
4785:
4509:
3676:
3001:
Continuous wave (CW) radar. Using frequency modulation allows range to be extracted.
1565:
Additional filtering and pulse integration modifies the radar equation slightly for
1405:
In the common case where the transmitter and the receiver are at the same location,
854:. Examples are breathing pattern detection for sleep monitoring and hand and finger
386:
to conduct an extensive review of available shortwave units. Wilkins would select a
382:
transmission. Requiring a suitable receiver for such studies, he told the "new boy"
191:
6582:
6553:
4754:
Kostenko, A.A., A.I. Nosich, and I.A. Tishchenko, "Radar Prehistory, Soviet Side,"
4632:
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in predetermined directions. When these signals contact an object they are usually
810:
779:
751:
684:
470:
458:
330:. In 1897, while testing this equipment for communicating between two ships in the
296:
261:
249:
226:
167:
6925:
6633:
5173:
3164:
976:, although radio waves are invisible to the human eye as well as optical cameras.
548:
at night. This design was followed by a pulsed system demonstrated in May 1935 by
6920:
6915:
6750:
6745:
5996:
5938:
5596:
5573:
4240:
4196:
4114:
Coherent microwave amplifiers operating above 1,000 watts microwave output, like
4007:
3951:
3650:
3592:
3417:
3284:
3020:
2806:
Doppler processing, which uses filters to separate clutter from desirable signals
2705:
2569:
caused by electron transit through amplification devices, which is reduced using
1833:
1635:
1552:{\displaystyle P_{r}={{P_{t}G_{t}A_{r}\sigma F^{4}} \over {{(4\pi )}^{2}R^{4}}}.}
925:
either toward or away from the transmitter, there will be a slight change in the
918:
851:
838:
724:
696:
558:
474:
218:
202:
143:
108:
88:
84:
6535:
E. Fishler; A. Haimovich; R. Blum; D. Chizhik; L. Cimini; R. Valenzuela (2004).
4191:
in which it operates permanently or temporarily. Typical radar utilizations are
3539:
surveillance radars now use this approach in preference to a parabolic antenna.
195:
7077:
6821:
6324:
Not an Ordinary Life. How Changing Times Brought Historical Events into my Life
5564:
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3744:
3690:
3642:
3617:
3391:
3108:
2971:
2967:
2949:
2793:
Clutter moves with the wind or is stationary. Two common strategies to improve
2575:
2494:
The maximum range of conventional radar can be limited by a number of factors:
953:
930:
814:
688:
650:
627:
586:
In 1935, Watson-Watt was asked to judge recent reports of a German radio-based
522:
434:
398:
307:
280:
171:
147:
135:
6601:
5785:. Madrid, Spain: Instituto de Física Aplicada, CETEF "L. Torres Quevedo", CSIC
5658:
4034:
Very strongly absorbed by atmospheric oxygen, which resonates at 60 GHz.
3697:. For this reason, a wide variety of wavelengths are used in different roles.
3627:
radar was considered to be the world's most powerful fighter radar, until the
1602:
802:
radar systems are used to monitor and regulate ship movements in busy waters.
7071:
6760:
6689:
6646:
4524:
4335:
4255:
4245:
4230:
4192:
3939:
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3490:
3398:
3324:
3280:
3195:
3172:
axis represents individual samples taken in between each transmit pulse. The
3120:
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2756:
2744:
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2566:
2523:
2484:
1631:
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731:
638:
394:
233:
116:
112:
6586:
5572:(Technical report). RADC Technical Reports. Vol. 1980. Rome, New York:
5438:
4768:
4087:
Hybrid mixers, fed by a waveform generator and an exciter for a complex but
782:
aircraft. Aircraft can land in fog at airports equipped with radar-assisted
7056:
6426:
4081:
3907:
3843:
3712:
3599:
3580:
3573:
3565:
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3551:
2556:
2279:
1569:, which can be used to increase detection range and reduce transmit power.
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600:
564:
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214:
163:
100:
6132:
Secret Location: A witness to the Birth of Radar and its Postwar Influence
5918:". The Radar Pages. (History and details of various British radar systems)
5720:
5287:
1010:
travelling through one material meet another material, having a different
653:" for collecting reports of enemy aircraft and coordinating the response.
6956:
6770:
4519:
4446:
4235:
4136:
3958:
3613:
3439:
3354:
2910:
2909:
Mainlobe jamming can generally only be reduced by narrowing the mainlobe
2548:
2532:
1817:{\displaystyle F_{D}=2\times F_{T}\times \left({\frac {V_{R}}{C}}\right)}
1079:
890:
876:
545:
230:
127:
6634:
A set of educational videos created for air traffic control (ATC) staff.
5914:
5806:"Polyalphaolefins: A New Improved Cost Effective Aircraft Radar Coolant"
4552:
2657:
for each stage. The signal can also be split among multiple filters for
326:
tube for detecting distant lightning strikes. The next year, he added a
310:
showed that radio waves could be reflected from solid objects. In 1895,
271:
Other systems which are similar to radar make use of other parts of the
6534:
6451:
5956:
5019:"The history of radar, from aircraft radio detectors to airborne radar"
4500:
4350:
4140:
4061:
4015:
4011:
4002:
3837:
3130:
It is possible to make a Doppler radar without any pulsing, known as a
3101:
2850:
2786:(meteorological radars wish for the opposite effect, and therefore use
2752:
2736:
2724:
2720:
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2623:
2570:
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1607:
906:
894:
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615:
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422:
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331:
104:
66:
6557:
6334:(Pages 36–67 contain the experiences of a WAAF radar plotter in WWII.)
2586:
clear sky, where the scene is so "cold" that it generates very little
2219:{\displaystyle |V_{R}|<{\frac {F_{R}\times {\frac {C}{F_{T}}}}{4}}}
217:
to locate landmarks and other ships, aircraft anti-collision systems,
6811:
6755:
6544:
Mark R. Bell (1993). "Information theory and radar waveform design".
5135:(Press release). The Patent Office. 10 September 2001. Archived from
5084:
4653:"Remote Sensing Core Curriculum: Radio Detection and Ranging (RADAR)"
4637:
4612:
4073:
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as they combine good reception qualities with reasonable resolution.
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Waveform design for active sensing systems: a computational approach
4951:
Butement, W. A. S., and P. E. Pollard; "Coastal Defence Apparatus",
3341:
622:
6981:
6864:
6859:
6854:
6079:
A radar history of World War II: technical and military imperatives
4431:
4290:
4135:) was used in several military radars in the 1970s. However, it is
4129:
4125:
4119:
4092:
3475:
3444:
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3358:
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2288:
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surface, such as rocks or soil, and are used by navigation radars.
1581:
1078:. These precautions do not totally eliminate reflection because of
914:
775:
518:
159:
96:
5661:
on 30 October 2021 – via YouTube; jaglavaksoldier's Channel.
5403:"Stopped Vehicle Detection (SVD) Comparison with Automotive Radar"
3060:
largely eliminating "noise" from the surfaces of bodies of water.
1646:
The Doppler frequency shift for active radar is as follows, where
6002:
Swords, Seán S., "Technical History of the Beginnings of Radar",
4109:
3975:
3920:
3911:
3903:
3596:
3143:
3124:
3100:
marks on the radar screen and then calculating the speed using a
3049:
2954:
2846:
2816:. Doppler separates clutter from aircraft and spacecraft using a
2262:
1900:{\displaystyle F_{D}=F_{T}\times \left({\frac {V_{R}}{C}}\right)}
822:
351:
323:
80:
71:
5460:
5026:
990:
541:
successfully tested a primitive surface-to-surface radar to aim
264:
and are capable of extracting useful information from very high
256:
for geological observations. Modern high tech radar systems use
33:
6849:
6430:
5999:
Early development and production by Chrysler Corp. during WWII.
5931:
5531:
A Canadian Perspective on High-Frequency Over-the-Horizon Radar
4914:
History of Communications-Electronics in the United States Navy
4039:
4023:
3892:
3855:
3825:
3621:
3616:. The first fighter aircraft to use phased array radar was the
3487:
2858:
1279:(area) of the receiving antenna; this can also be expressed as
1051:
1023:
574:
393:
By placing a transmitter and receiver on opposite sides of the
5109:[New obstacle detection system and its applications].
6714:
5961:
5715:
5107:"Nouveau système de repérage d'obstacles et ses applications"
4580:. Public Works and Government Services Canada. Archived from
4483:
4478:
4473:
4451:
4132:
3756:
3357:
that generates the radio signal with an oscillator such as a
3092:
3045:
1105:
returning to the receiving antenna is given by the equation:
610:
514:
453:, Anacostia, D. C., from the late 1930s (photo taken in 1945)
284:
276:
6167:
2803:
Moving target indication, which integrates successive pulses
2774:
between the radar transceiver and the antenna. In a typical
2501:
The maximum non-ambiguous range, which is determined by the
7051:
6602:
Mark A. Richards; James A. Scheer; William A. Holm (2010).
6449:
5915:
All you ever wanted to know about British air defence radar
5341:"These High-Tech Sensors May Be the Key to Autonomous Cars"
3053:
3397:
A display processor to produce signals for human readable
6520:. London: The Institution of Engineering and Technology.
6420:
6060:
RDF1: The Location of Aircraft by Radio Methods 1935–1945
5598:
Investigation of Terrain Bounce Electronic Countermeasure
4076:. They generate short pulses of power to feed, e.g., the
3801:
3770:
3223:
which prevents range from being determined directly, and
2981:
Distance may also be measured as a function of time. The
727:
that was used for many years in most radar applications.
596:
162:
use by several countries in the period before and during
6518:
Waveform design and diversity for advanced radar systems
6401:
6326:, Cardiff Centre for Lifelong Learning, Cardiff, 2009.,
4861:"Making waves: Robert Watson-Watt, the pioneer of radar"
2747:
events. This phenomenon is especially apparent near the
944:
are also used in order to recover useful radar signals.
809:
and wind. It has become the primary tool for short-term
6516:
Fulvio Gini; Antonio De Maio; Lee Patton, eds. (2012).
6354:
Britain's shield: radar and the defeat of the Luftwaffe
6249:
The radar war: Germany's pioneering achievement 1904-45
6208:
4546:"Chapter I – Terminology and technical characteristics"
3576:. The amount of cancellation is side-lobe suppression.
3251:, moving target detection processors, correlation with
488:
In France in 1934, following systematic studies on the
5631:"Ground Surveillance Radars and Military Intelligence"
5245:
5243:
6936:
RIM-174 Standard Extended Range Active Missile (SM-6)
6227:
3554:: Not all radar antennas must rotate to scan the sky.
2985:
is the time it takes for a radar pulse to travel one
2639:
2299:
2257:
is used to minimize the interference caused by rain.
2153:
2123:
2063:
2029:
2002:
1975:
1948:
1921:
1845:
1756:
1733:
1706:
1679:
1652:
1450:
1340:
1286:
1114:
994:
Brightness can indicate reflectivity as in this 1960
786:
systems in which the plane's position is observed on
626:
Memorial plaque commemorating Robert Watson-Watt and
6284:
6265:
4286:
3957:, meaning 'short'. Limited use due to absorption by
3820:, making them useful in the missile detection role.
3231:
3111:. Most modern radar systems use this principle into
190:
has since entered English and other languages as an
43:, used to track space objects and ballistic missiles
6478:
Signal Design for Active Sensing and Communications
5803:
5240:
5078:
3219:large dynamic range. Military applications require
5721:"Multi-function Phased Array Radar (MPAR) Project"
5486:
4728:
4575:
3271:processing are also used in clutter environments.
3153:
2812:The most effective clutter reduction technique is
2649:
2473:θe : elevation angle above the radar horizon
2456:
2218:
2136:
2106:
2042:
2015:
1988:
1961:
1934:
1899:
1816:
1739:
1719:
1692:
1665:
1551:
1346:
1320:
1232:
6303:
5236:. Bonnier Corporation. December 1941. p. 56.
3702:Institute of Electrical and Electronics Engineers
1321:{\displaystyle {G_{r}\lambda ^{2}} \over {4\pi }}
505:During the same period, Soviet military engineer
7069:
6168:Derek Howse; Naval Radar Trust (February 1993).
5566:A model for high frequency radar auroral clutter
5288:"The Wizard War: WW2 & The Origins of Radar"
5068:. Bonnier Corporation. October 1935. p. 29.
4729:Fakhrul Razi Ahmad, Zakuan; et al. (2018).
4714:: CS1 maint: bot: original URL status unknown (
2770:Some clutter may also be caused by a long radar
2759:produces convection patterns in the ionospheric
2727:, animals (especially birds), turbulence in the
6628:MIT Video Course: Introduction to Radar Systems
6351:
6246:
6230:Principles of radar and sonar signal processing
6022:The radar army: winning the war of the airwaves
5523:
5521:
5257:. Hearst Magazines. September 1941. p. 26.
5201:"How the search for a 'death ray' led to radar"
5161:Improvements in or relating to wireless systems
5117:on 16 January 2009 – via radar-france.fr.
4985:. Hearst Magazines. December 1935. p. 844.
4756:Proc. of IEEE APS International Symposium 2001,
3711:Other users of the radio spectrum, such as the
1942:) is pulsed, using a pulse repeat frequency of
563:in Germany and then another in June 1935 by an
485:generated its radar technology during the war.
6802:Joint Tactical Information Distribution System
6676:
6474:
5675:. Applied Technology Institute. Archived from
5604:(Thesis). Wright-Patterson AFB, Dayton, Ohio:
4557:. International Telecommunications Union (ITU)
2918:to detect and disregard non-mainlobe signals.
6891:Space Tracking and Surveillance System (STSS)
6865:AN/SPY-6 Air and Missile Defense Radar (AMDR)
6662:
6148:
6095:
6057:
5979:Radar Navigation and Maneuvering Board Manual
5537:(Technical report). Ottawa, Ontario, Canada:
4979:"Radio Waves Warn Liner of Obstacles in Path"
3846:; 'L' for 'long'. Widely used for long range
2475:ha : height of the feedhorn above ground
2107:{\displaystyle |F_{D}|<{\frac {F_{R}}{2}}}
1392:= distance from the transmitter to the target
746:), and complementary navigation systems like
494:Compagnie générale de la télégraphie sans fil
6604:Principles of Modern Radar: Basic Principles
6543:
6377:
5518:
4953:Inventions Book of the Royal Engineers Board
4689:. Archived from the original on 2 March 2023
3274:
1042:substances, is used on military vehicles to
618:tower in Great Baddow, Essex, United Kingdom
186:for "radio detection and ranging". The term
6170:Radar at sea: the royal Navy in World War 2
6076:
5777:
5251:"Odd-shaped Boats Rescue British Engineers"
5171:
3376:that links the transmitter and the antenna.
3239:is employed in radar systems to reduce the
2763:. Radar clutter can degrade the ability of
2467: r : distance radar-target
1401:= distance from the target to the receiver.
7113:Science and technology during World War II
6669:
6655:
6209:Colin Latham; Anne Stobbs (January 1997).
6186:
6038:
5948:Introduction to Naval Weapons Engineering.
5553:
1377:, or scattering coefficient, of the target
6129:
5894:Learn how and when to remove this message
5113:(in French). 20 July 1934. Archived from
5099:
5051:, Doubleday Anchor, New York, 1962, p. 66
4761:
4636:
91:of objects relative to the site. It is a
16:Object detection system using radio waves
6266:Merrill Ivan Skolnik (1 December 1980).
6019:
6009:, Vol. 6, London: Peter Peregrinus, 1986
5941:The secret development of British radar.
5594:
5527:
5008:, vol. 2, no. 3 (Jul. 1972), pp. 241–263
4968:, Peter Peregrinus, Ltd, 1986, pp. 71–74
4966:tech. History of the Beginnings of Radar
4537:
3587:). They are the heart of the ship-borne
3564:Another method of steering is used in a
3546:
3523:
3459:
3421:
3407:A link to end user devices and displays.
3340:
3297:There are four common track algorithms.
3163:
2996:
2953:
2691:
2287:
1601:
989:
917:, and wet ground. This makes the use of
870:
761:
670:
621:
609:
573:
444:
6546:IEEE Transactions on Information Theory
6537:MIMO radar: an idea whose time has come
5625:
5623:
5539:Defence Research and Development Canada
5513:
5484:
5310:"AIS vs Radar: Vessel Tracking Options"
5198:
4530:
4169:International Telecommunication Union's
3243:. Signal processing techniques include
2992:
2938:
2611:is bandwidth (post matched filter) and
2551:by at least the signal-to-noise ratio.
1093:
521:, entered into service in June 1943 on
7070:
6792:Aegis Ballistic Missile Defense System
5559:
5493:. SciTech Publishing Inc. p. 98.
5285:
4926:
4907:
4371:Acronyms and abbreviations in avionics
4072:, and a high voltage switch such as a
3455:
2273:
660:
637:, Bawdsey Research Station located in
595:of 26 February 1935, using a powerful
440:
6650:
5541:. p. 38. DRDC Ottawa TM 2006-285
5338:
4463:Similar detection and ranging methods
3706:International Telecommunication Union
3168:Pulse-Doppler signal processing. The
721:Massachusetts Institute of Technology
461:, researchers in the United Kingdom,
6842:
6371:
5967:Penley, Bill, and Jonathan Penley, "
5850:
5655:"AN/PPS-5 Ground Surveillance Radar"
5620:
5595:Strasser, Nancy C. (December 1980).
5174:"Briefcase 'that changed the world'"
5165:
5072:
4769:"Christian Huelsmeyer, the inventor"
4266:Synthetically thinned aperture radar
3625:Passive electronically scanned array
3519:
3474:More modern systems use a steerable
3087:
3063:
2933:
2700:from a target cause ghosts to appear
875:3D Doppler radar spectrum showing a
805:Meteorologists use radar to monitor
511:Leningrad Electrotechnical Institute
301:
6886:Space-Based Infrared System (SBIRS)
6797:Active electronically scanned array
6402:Nadav Levanon; Eli Mozeson (2004).
5129:"British man first to patent radar"
4543:
3842:Long range air traffic control and
3632:Active electronically scanned array
3426:AS-3263/SPS-49(V) antenna (US Navy)
2547:requires a signal that exceeds the
2268:
306:As early as 1886, German physicist
13:
6896:Space Surveillance Telescope (SST)
6341:. Cardiff. Candy Jar Books. 2011.
5657:. 29 December 2009. Archived from
5528:Riddolls, Ryan J (December 2006).
5025:. 17 February 2015. Archived from
3670:
3436:omnidirectional broadcast antennas
605:Air Member for Supply and Research
14:
7144:
6931:RIM-161 Standard Missile 3 (SM-3)
6621:
6352:David Zimmerman (February 2001).
5717:National Severe Storms Laboratory
5606:Air Force Institute of Technology
5419:from the original on 9 June 2024.
5368:""AWACS: Nato's eyes in the sky""
5339:Quain, John (26 September 2019).
5307:
4623:(3857): 391–392. 2 October 1943.
4211:
3411:
3240:
3232:Reduction of interference effects
2826:time-domain pulse-amplitude radar
1587:
578:The first workable unit built by
322:, developed an apparatus using a
158:Radar was developed secretly for
5924:Telephone History: Radar History
5855:
5673:"Fundamentals of Radar Tracking"
5081:"The story of RADAR Development"
4681:
4303:
4289:
3497:
3314:Interactive Multiple Model (IMM)
3199:accidents. Weather radar uses a
2590:. The thermal noise is given by
940:. More sophisticated methods of
95:method used to detect and track
48:
32:
6567:IEEE Signal Processing Magazine
6247:David Pritchard (August 1989).
5950:". (Radar fundamentals section)
5846:
5830:
5797:
5771:
5753:
5735:
5709:
5683:
5665:
5647:
5588:
5507:
5478:
5453:
5423:
5395:
5381:
5360:
5332:
5301:
5286:Goebel, Greg (1 January 2007).
5279:
5261:
5222:
5199:Harford, Tim (9 October 2017).
5192:
5172:Angela Hind (5 February 2007).
5143:
5121:
5054:
5041:
5011:
4998:
4989:
4971:
4958:
4945:
4920:
4901:
4892:
4867:
4853:
4827:
4805:
4792:
4779:
4205:radiolocation-satellite service
3814:ballistic missile early warning
3765:(OTH) radars; 'high frequency'
3542:
3365:and controls its duration by a
3249:Pulse-Doppler signal processing
3160:Pulse-Doppler signal processing
3154:Pulse-Doppler signal processing
3019:and is often found in aircraft
2943:
2675:Interference (wave propagation)
2668:
2659:pulse-Doppler signal processing
2233:
1828:Passive radar is applicable to
1567:pulse-Doppler radar performance
963:
866:
757:
449:Experimental radar antenna, US
397:in 1922, U.S. Navy researchers
7133:Wireless communication systems
7123:Radio stations and systems ITU
6870:Sea-based X-band Radar (SBX-1)
6460:. Cambridge University Press.
6435:. Cambridge University Press.
6406:. John Wiley & Sons, Inc.
6306:Introduction to airborne radar
6228:François Le Chevalier (2002).
5489:Introduction to Airborne Radar
4748:
4722:
4684:"History of Radar Meteorology"
4675:
4645:
4605:
4596:
4569:
4383:Amplitude-comparison monopulse
4151:
3869:ground controlled interception
3330:
3307:Probabilistic Data Association
3257:space-time adaptive processing
3015:This technique can be used in
2894:from the jammer to the radar (
2797:in a clutter environment are:
2409:
2396:
2349:
2325:
2170:
2155:
2080:
2065:
1610:caused by motion of the source
1584:effects are also considered.
1523:
1514:
1187:
1178:
929:of the radio waves due to the
421:and P. E. Pollard developed a
378:before turning his inquiry to
314:, a physics instructor at the
1:
6639:Glossary of radar terminology
6285:Merrill Ivan Skolnik (1990).
6268:Introduction to radar systems
6039:E.G. Bowen (1 January 1998).
5906:
5878:and help improve the section.
5230:"Night Watchmen of the Skies"
5062:"Mystery Ray Locates 'Enemy'"
4613:"Radio Detection and Ranging"
4199:, these might operate in the
4056:
2920:Other anti-jamming techniques
1915:When the transmit frequency (
979:
861:
848:Intelligent Transport Systems
492:, the research branch of the
126:A radar system consists of a
6997:Mark 8 Fire Control Computer
6992:Mark I Fire Control Computer
6977:Comprehensive Display System
6730:Ship gun fire-control system
6289:. McGraw-Hill Professional.
6149:Peter S. Hall (March 1991).
6058:Michael Bragg (1 May 2002).
6007:History of Technology Series
5804:Stropki, Michael A. (1992).
5079:Alan Dower Blumlein (2002).
4356:Radar signal characteristics
3434:Early systems tended to use
3311:Multiple Hypothesis Tracking
3253:secondary surveillance radar
2483:of air, which is called the
1383:= pattern propagation factor
885:Radar signal characteristics
829:, precipitation types, etc.
509:, in collaboration with the
166:. A key development was the
7:
6232:. Artech House Publishers.
6191:. Wordsworth Editions Ltd.
5988:Radar – The Great Detective
5576:. p. 9. RADC-TR-80-122
5574:Rome Air Development Center
4931:. Springer. pp. 5–66.
4908:Howeth, Linwood S. (1963).
4576:Translation Bureau (2013).
4282:
4187:shall be classified by the
3704:and internationally by the
3636:Lockheed Martin F-22 Raptor
3302:Nearest neighbour algorithm
2872:Radar jamming and deception
2650:{\displaystyle {\sqrt {2}}}
1441:is the range. This yields:
1363:= gain of receiving antenna
1266:of the transmitting antenna
744:air-to-surface-vessel radar
736:aircraft interception radar
279:, which uses predominantly
69:to determine the distance (
10:
7149:
6972:Naval Tactical Data System
6677:NATO naval weapons systems
6378:M I. Skolnik, ed. (1970).
6304:George W. Stimson (1998).
6187:R.V. Jones (August 1998).
6013:
5431:"The Technology Behind S+"
4322:
4316:
4189:radiocommunication service
4107:
4103:
3717:electronic countermeasures
3677:Radio spectrum § IEEE
3674:
3557:
3531:
3467:
3464:Surveillance radar antenna
3415:
3349:A radar's components are:
3334:
3278:
3241:radar interference effects
3225:range ambiguity resolution
3206:The alternate purpose is "
3157:
3067:
3004:
2966:(ranging) is based on the
2947:
2869:
2865:
2751:, where the action of the
2703:
2687:
2672:
2517:
2503:pulse repetition frequency
2277:
2237:
2117:Or when substituting with
1830:electronic countermeasures
1591:
983:
882:
837:to map the composition of
784:ground-controlled approach
683:A key development was the
679:radar operators in England
664:
537:. The following year, the
358:harbour but was rejected.
294:
290:
178:was coined in 1940 by the
18:
7047:
7021:
6944:
6908:
6878:
6835:
6779:
6738:
6710:Combat information center
6682:
6172:. Naval Institute Press.
4835:"gdr_zeichnungpatent.jpg"
4442:Radar engineering details
4388:Constant false alarm rate
4185:radiodetermination system
4181:radiodetermination system
3528:Slotted waveguide antenna
3337:Radar engineering details
3275:Plot and track extraction
3265:Constant false alarm rate
2832:Constant false alarm rate
2292:Echo heights above ground
2246:electromagnetic radiation
1634:, military aircraft, and
1622:Sea-based radar systems,
835:ground-penetrating radars
535:Naval Research Laboratory
451:Naval Research Laboratory
412:Naval Research Laboratory
258:digital signal processing
248:target locating systems,
196:losing all capitalization
7010:USN early guided weapons
6539:. IEEE Radar Conference.
6211:Radar: A Wartime Miracle
6100:. Simon & Schuster.
6081:. Taylor & Francis.
6043:. Taylor & Francis.
5937:12 December 2005 at the
5485:Stimson, George (1998).
4879:The Lemelson-MIT Program
4863:. BBC. 16 February 2017.
4393:Sensitivity time control
4261:Synthetic-aperture radar
3245:moving target indication
2633:can improve noise up to
2631:moving target indication
2513:
1727:is radial velocity, and
1624:semi-active radar homing
1617:moving target indication
1572:The equation above with
1354:= transmitted wavelength
1347:{\displaystyle \lambda }
1032:Radar absorbing material
788:precision approach radar
740:maritime patrol aircraft
717:MIT Radiation Laboratory
273:electromagnetic spectrum
254:ground-penetrating radar
6587:10.1109/MSP.2008.930414
6481:. Elanders Sverige AB.
6475:M. Soltanalian (2014).
6322:Younghusband, Eileen.,
5780:"Physics of Outgassing"
5691:"Side-Lobe Suppression"
4657:University of Minnesota
4422:Crossed-field amplifier
4331:Terrain-following radar
3761:Coastal radar systems,
3695:over the horizon radars
3620:. The MiG-31M's SBI-16
3140:time-frequency analysis
2916:omnidirectional antenna
2822:moving target indicator
2795:measures of performance
2776:plan position indicator
2729:atmospheric circulation
2541:measures of performance
2471:ae : Earth radius
1747:is the speed of light:
1700:is transmit frequency,
1044:reduce radar reflection
1028:electrically conductive
911:electrical conductivity
477:, the Netherlands, the
384:Arnold Frederic Wilkins
376:radio direction finding
142:domain, a transmitting
7103:Navigational equipment
6921:RIM-67 Standard (SM-2)
6766:Close-in weapon system
6606:. SciTech Publishing.
6337:Younghusband, Eileen.
6308:. SciTech Publishing.
6096:Robert Buderi (1996).
5761:"Fully Coherent Radar"
4273:Over-the-horizon radar
4209:
4014:avoidance systems for
3812:Very long range (e.g.
3790:< 300 MHz
3665:airborne radar systems
3634:was introduced on the
3593:Patriot Missile System
3555:
3529:
3465:
3427:
3346:
3214:flying techniques and
3182:
3002:
2959:
2847:ionospheric reflection
2836:automatic gain control
2765:over-the-horizon radar
2701:
2651:
2489:curvature of the Earth
2476:
2458:
2284:Over-the-horizon radar
2220:
2138:
2108:
2044:
2017:
1990:
1963:
1936:
1901:
1818:
1741:
1721:
1694:
1673:is Doppler frequency,
1667:
1611:
1553:
1348:
1322:
1234:
1003:
913:—such as most metals,
880:
800:vessel traffic service
767:
709:attack on Pearl Harbor
680:
630:
619:
583:
454:
242:flight control systems
65:is a system that uses
21:Radar (disambiguation)
7098:Measuring instruments
7029:Ground-based systems:
6962:Torpedo Data Computer
6952:Radar in World War II
6153:. Potomac Books Inc.
6118:, McGraw Hill, 2005,
6062:. Twayne Publishers.
5693:. MIT. Archived from
5643:on 22 September 2010.
5047:Page, Robert Morris,
4927:Coales, J.F. (1995).
4875:"Robert Wattson-Watt"
4226:Continuous-wave radar
4201:radiolocation service
4177:
4173:ITU Radio Regulations
4116:travelling wave tubes
4070:pulse forming network
3724:Radar frequency bands
3550:
3527:
3463:
3425:
3344:
3269:digital terrain model
3167:
3132:continuous-wave radar
3017:continuous wave radar
3000:
2957:
2948:Further information:
2855:anomalous propagation
2784:circular polarization
2695:
2682:signal-to-noise ratio
2652:
2537:signal-to-noise ratio
2459:
2291:
2255:circular polarization
2238:Further information:
2221:
2139:
2137:{\displaystyle F_{D}}
2109:
2045:
2043:{\displaystyle F_{R}}
2018:
2016:{\displaystyle F_{R}}
1991:
1989:{\displaystyle F_{T}}
1964:
1962:{\displaystyle F_{R}}
1937:
1935:{\displaystyle F_{T}}
1902:
1819:
1742:
1722:
1720:{\displaystyle V_{R}}
1695:
1693:{\displaystyle F_{T}}
1668:
1666:{\displaystyle F_{D}}
1605:
1554:
1433:² can be replaced by
1349:
1323:
1235:
1008:electromagnetic waves
993:
970:electromagnetic waves
938:electronic amplifiers
889:A radar system has a
883:Further information:
874:
852:detect human movement
765:
715:organized the secret
674:
667:Radar in World War II
625:
613:
577:
490:split-anode magnetron
448:
370:and the detection of
334:, he took note of an
328:spark-gap transmitter
316:Imperial Russian Navy
132:electromagnetic waves
7093:Microwave technology
7088:Aircraft instruments
6077:Louis Brown (1999).
5995:28 July 2020 at the
4531:Notes and references
4457:Travelling-wave tube
4146:Pollution Prevention
3961:at 22 GHz, so K
3848:early warning radars
3208:look-down/shoot-down
3142:(Weyl Heisenberg or
3077:early warning radars
3007:Frequency modulation
2993:Frequency modulation
2964:distance measurement
2962:One way to obtain a
2939:Distance measurement
2637:
2580:List of UWB channels
2297:
2240:Polarization (waves)
2151:
2121:
2061:
2027:
2000:
1973:
1946:
1919:
1843:
1754:
1731:
1704:
1677:
1650:
1448:
1338:
1283:
1112:
1094:Radar range equation
1016:diamagnetic constant
986:Reflection (physics)
841:. Police forces use
341:The German inventor
238:radar remote sensing
211:anti-missile systems
19:For other uses, see
7118:Targeting (warfare)
7108:Air traffic control
6987:Specific equipment:
6827:List of radar types
6807:Historical systems:
6787:Aegis Combat System
6705:Director (military)
6695:Fire-control system
6579:2009ISPM...26...32C
6450:Solomon W. Golomb;
5984:Wesley Stout, 1946
5970:Early Radar History
5954:Hollmann, Martin, "
5275:. 16 February 2017.
5049:The Origin of Radar
4910:"Ch. XXXVIII Radar"
4841:on 24 February 2015
4758:vol. 4. p. 44, 2003
4629:1943Natur.152..391.
4437:Omniview technology
4361:Pulse doppler radar
4319:List of radar types
3726:
3655:thinned array curse
3589:Aegis Combat System
3456:Parabolic reflector
3261:track-before-detect
3117:pulse-Doppler radar
2843:atmospheric ducting
2814:pulse-Doppler radar
2788:linear polarization
2767:to detect targets.
2520:Noise (electronics)
2274:Beam path and range
2259:Linear polarization
1996:with a distance of
1628:active radar homing
1598:Pulse-Doppler radar
1375:radar cross section
1253:= transmitter power
1226:
1211:
1088:radar cross section
1067:reflective surfaces
1056:Rayleigh scattering
1012:dielectric constant
811:weather forecasting
725:monopulse technique
661:During World War II
593:Daventry Experiment
441:Before World War II
388:General Post Office
343:Christian Hülsmeyer
207:air-defense systems
7039:Kerrison Predictor
6700:Fire-control radar
6356:. Sutton Pub Ltd.
6213:. Sutton Pub Ltd.
6130:Ian Goult (2011).
6116:Radar For Mariners
5932:WW2 Shadow Factory
5679:on 24 August 2011.
5346:The New York Times
5320:on 2 February 2019
5111:BREVET D'INVENTION
4578:"Radar definition"
4346:Inverse-square law
4297:Electronics portal
4251:Planar array radar
3793:> 1 m
3722:
3683:order of magnitude
3661:Aperture synthesis
3647:aperture synthesis
3556:
3530:
3466:
3428:
3347:
3216:stealth technology
3183:
3148:chirplet transform
3146:), as well as the
3040:available via the
3003:
2960:
2888:inverse-square law
2879:electronic warfare
2818:frequency spectrum
2741:geomagnetic storms
2702:
2647:
2620:Boltzmann constant
2539:are two different
2477:
2454:
2216:
2134:
2104:
2040:
2013:
1986:
1959:
1932:
1897:
1814:
1737:
1717:
1690:
1663:
1612:
1549:
1344:
1309:
1277:effective aperture
1230:
1212:
1197:
1004:
881:
768:
681:
631:
620:
584:
580:Robert Watson-Watt
571:in Great Britain.
569:Robert Watson-Watt
539:United States Army
455:
408:Lawrence A. Hyland
363:Robert Watson-Watt
223:space surveillance
219:ocean surveillance
180:United States Navy
117:weather formations
93:radiodetermination
7065:
7064:
7034:Gun data computer
6904:
6903:
6558:10.1109/18.259642
6488:978-91-554-9017-1
6442:978-1-107-01969-0
6372:Technical reading
6363:978-0-7509-1799-5
6347:978-0-9566826-2-8
6332:978-0-9561156-9-0
6315:978-1-891121-01-2
6296:978-0-07-057913-2
6277:978-0-07-066572-9
6258:978-1-85260-246-8
6251:. Harpercollins.
6239:978-1-58053-338-6
6220:978-0-7509-1643-1
6198:978-1-85326-699-7
6179:978-1-55750-704-4
6160:978-0-08-037711-7
6141:978-0-7524-5776-5
6134:. History Press.
6124:978-0-07-139867-1
6114:Burch, David F.,
6107:978-0-684-81021-8
6088:978-0-7503-0659-1
6069:978-0-9531544-0-1
6050:978-0-7503-0586-0
6031:978-0-7090-4508-3
6020:Reg Batt (1991).
5957:Radar Family Tree
5904:
5903:
5896:
5778:J.L. de Segovia.
5743:"Radar Modulator"
5500:978-1-891121-01-2
5441:on 27 August 2016
5435:Sleep.mysplus.com
5410:Ogier Electronics
5255:Popular Mechanics
5205:BBC World Service
4983:Popular Mechanics
4938:978-1-349-13457-1
4682:Duda, Jeffrey D.
4584:on 4 January 2014
4554:Radio Regulations
4490:Historical radars
4469:Acoustic location
4277:Chirp transmitter
4097:pulse compression
4054:
4053:
3986:0.75–1.11 cm
3947:1.11–1.67 cm
3806:300–1000 MHz
3653:. Because of the
3585:Safeguard Program
3534:Slotted waveguide
3520:Slotted waveguide
3470:Parabolic antenna
3237:Signal processing
3188:spectrum analyzer
3088:Speed measurement
3070:Pulse compression
3064:Pulse compression
2934:Signal processing
2924:frequency hopping
2749:geomagnetic poles
2645:
2412:
2214:
2208:
2102:
2052:Nyquist frequency
1891:
1808:
1740:{\displaystyle C}
1544:
1318:
1228:
958:ultraviolet light
942:signal processing
856:gesture detection
813:and watching for
713:Alfred Lee Loomis
703:Popular Mechanics
647:Battle of Britain
533:, working at the
336:interference beat
302:First experiments
275:. One example is
250:self-driving cars
194:, a common noun,
39:Long-range radar
7140:
7128:1940s neologisms
7014:
7008:
6926:MIM-104F (PAC-3)
6840:
6839:
6780:Specific systems
6671:
6664:
6657:
6648:
6647:
6617:
6613:978-1891121-52-4
6598:
6561:
6552:(5): 1578–1597.
6540:
6531:
6512:
6506:
6502:
6500:
6492:
6471:
6446:
6417:
6398:
6386:
6367:
6319:
6300:
6281:
6262:
6243:
6224:
6202:
6183:
6164:
6145:
6111:
6092:
6073:
6054:
6035:
5972:—an Introduction
5912:Barrett, Dick, "
5899:
5892:
5888:
5885:
5879:
5874:Please read the
5870:may need cleanup
5859:
5858:
5851:
5840:
5834:
5828:
5827:
5825:
5823:
5817:
5810:
5801:
5795:
5794:
5792:
5790:
5784:
5775:
5769:
5768:
5765:radartutorial.eu
5757:
5751:
5750:
5747:radartutorial.eu
5739:
5733:
5732:
5730:
5728:
5713:
5707:
5706:
5704:
5702:
5697:on 31 March 2012
5687:
5681:
5680:
5669:
5663:
5662:
5651:
5645:
5644:
5642:
5635:
5627:
5618:
5617:
5615:
5613:
5608:. pp. 1–104
5603:
5592:
5586:
5585:
5583:
5581:
5571:
5557:
5551:
5550:
5548:
5546:
5536:
5525:
5516:
5515:
5511:
5505:
5504:
5492:
5482:
5476:
5475:
5473:
5471:
5457:
5451:
5450:
5448:
5446:
5437:. Archived from
5427:
5421:
5420:
5418:
5407:
5399:
5393:
5392:
5385:
5379:
5378:
5372:
5364:
5358:
5357:
5355:
5353:
5336:
5330:
5329:
5327:
5325:
5316:. Archived from
5305:
5299:
5298:
5296:
5294:
5283:
5277:
5276:
5265:
5259:
5258:
5247:
5238:
5237:
5226:
5220:
5219:
5213:
5211:
5196:
5190:
5189:
5183:
5181:
5169:
5163:
5158:
5157:
5153:
5147:
5141:
5140:
5139:on 19 July 2006.
5125:
5119:
5118:
5103:
5097:
5096:
5094:
5092:
5083:. Archived from
5076:
5070:
5069:
5058:
5052:
5045:
5039:
5038:
5036:
5034:
5015:
5009:
5002:
4996:
4993:
4987:
4986:
4975:
4969:
4962:
4956:
4949:
4943:
4942:
4924:
4918:
4917:
4905:
4899:
4896:
4890:
4889:
4887:
4885:
4871:
4865:
4864:
4857:
4851:
4850:
4848:
4846:
4837:. Archived from
4831:
4825:
4820:
4819:
4815:
4809:
4803:
4796:
4790:
4783:
4777:
4776:
4765:
4759:
4752:
4746:
4745:
4743:
4741:
4726:
4720:
4719:
4713:
4705:
4696:
4694:
4688:
4679:
4673:
4672:
4670:
4668:
4659:. Archived from
4649:
4643:
4642:
4640:
4638:10.1038/152391b0
4609:
4603:
4600:
4594:
4593:
4591:
4589:
4573:
4567:
4566:
4564:
4562:
4550:
4541:
4515:Hohentwiel radar
4427:Gallium arsenide
4417:Cavity magnetron
4341:Radar navigation
4313:
4311:Geography portal
4308:
4307:
4306:
4299:
4294:
4293:
4163:) is defined by
3931:1.67–2.5 cm
3900:2.5–3.75 cm
3884:3.75–7.5 cm
3818:nuclear blackout
3763:over-the-horizon
3736:Wavelength range
3727:
3721:
3513:Conical scanning
3345:Radar components
3228:identification.
3212:nap-of-the-earth
3037:modulation index
3021:radar altimeters
2904:sidelobe jamming
2896:mainlobe jamming
2696:Radar multipath
2656:
2654:
2653:
2648:
2646:
2641:
2607:is temperature,
2481:refractive index
2463:
2461:
2460:
2455:
2453:
2452:
2440:
2439:
2430:
2429:
2417:
2413:
2408:
2407:
2386:
2385:
2376:
2375:
2357:
2356:
2347:
2346:
2337:
2336:
2321:
2320:
2311:
2269:Limiting factors
2225:
2223:
2222:
2217:
2215:
2210:
2209:
2207:
2206:
2194:
2189:
2188:
2178:
2173:
2168:
2167:
2158:
2143:
2141:
2140:
2135:
2133:
2132:
2113:
2111:
2110:
2105:
2103:
2098:
2097:
2088:
2083:
2078:
2077:
2068:
2049:
2047:
2046:
2041:
2039:
2038:
2022:
2020:
2019:
2014:
2012:
2011:
1995:
1993:
1992:
1987:
1985:
1984:
1968:
1966:
1965:
1960:
1958:
1957:
1941:
1939:
1938:
1933:
1931:
1930:
1906:
1904:
1903:
1898:
1896:
1892:
1887:
1886:
1877:
1868:
1867:
1855:
1854:
1823:
1821:
1820:
1815:
1813:
1809:
1804:
1803:
1794:
1785:
1784:
1766:
1765:
1746:
1744:
1743:
1738:
1726:
1724:
1723:
1718:
1716:
1715:
1699:
1697:
1696:
1691:
1689:
1688:
1672:
1670:
1669:
1664:
1662:
1661:
1558:
1556:
1555:
1550:
1545:
1543:
1542:
1541:
1532:
1531:
1526:
1510:
1509:
1508:
1496:
1495:
1486:
1485:
1476:
1475:
1465:
1460:
1459:
1353:
1351:
1350:
1345:
1327:
1325:
1324:
1319:
1317:
1308:
1307:
1306:
1297:
1296:
1285:
1239:
1237:
1236:
1231:
1229:
1227:
1225:
1220:
1210:
1205:
1196:
1195:
1190:
1174:
1173:
1172:
1160:
1159:
1150:
1149:
1140:
1139:
1129:
1124:
1123:
1076:stealth aircraft
1071:corner reflector
919:radar altimeters
833:use specialized
780:United Air Lines
752:RAF's Pathfinder
685:cavity magnetron
562:
459:Second World War
435:Chain Home (low)
297:History of radar
262:machine learning
240:, altimetry and
168:cavity magnetron
85:elevation angles
52:
36:
7148:
7147:
7143:
7142:
7141:
7139:
7138:
7137:
7068:
7067:
7066:
7061:
7043:
7017:
7012:
7006:
6940:
6916:Harpoon missile
6900:
6874:
6831:
6775:
6751:Guided missiles
6746:Naval artillery
6734:
6678:
6675:
6644:
6624:
6614:
6528:
6504:
6503:
6494:
6493:
6489:
6468:
6443:
6414:
6395:
6387:. McGraw-Hill.
6384:
6374:
6364:
6339:One Woman's War
6316:
6297:
6278:
6270:. McGraw-Hill.
6259:
6240:
6221:
6199:
6189:Most Secret War
6180:
6161:
6142:
6108:
6089:
6070:
6051:
6032:
6016:
5997:Wayback Machine
5939:Wayback Machine
5909:
5900:
5889:
5883:
5880:
5873:
5866:Further reading
5860:
5856:
5849:
5844:
5843:
5835:
5831:
5821:
5819:
5815:
5808:
5802:
5798:
5788:
5786:
5782:
5776:
5772:
5759:
5758:
5754:
5741:
5740:
5736:
5726:
5724:
5714:
5710:
5700:
5698:
5689:
5688:
5684:
5671:
5670:
5666:
5653:
5652:
5648:
5640:
5633:
5629:
5628:
5621:
5611:
5609:
5601:
5593:
5589:
5579:
5577:
5569:
5558:
5554:
5544:
5542:
5534:
5526:
5519:
5512:
5508:
5501:
5483:
5479:
5469:
5467:
5465:Atap.google.com
5459:
5458:
5454:
5444:
5442:
5429:
5428:
5424:
5416:
5405:
5401:
5400:
5396:
5391:. 8 April 2019.
5387:
5386:
5382:
5370:
5366:
5365:
5361:
5351:
5349:
5337:
5333:
5323:
5321:
5306:
5302:
5292:
5290:
5284:
5280:
5267:
5266:
5262:
5249:
5248:
5241:
5234:Popular Science
5228:
5227:
5223:
5209:
5207:
5197:
5193:
5179:
5177:
5170:
5166:
5155:
5149:
5148:
5144:
5127:
5126:
5122:
5105:
5104:
5100:
5090:
5088:
5087:on 10 July 2011
5077:
5073:
5066:Popular Science
5060:
5059:
5055:
5046:
5042:
5032:
5030:
5029:on 20 June 2015
5017:
5016:
5012:
5006:Science Studies
5003:
4999:
4994:
4990:
4977:
4976:
4972:
4964:Swords, S. S.;
4963:
4959:
4950:
4946:
4939:
4925:
4921:
4906:
4902:
4897:
4893:
4883:
4881:
4873:
4872:
4868:
4859:
4858:
4854:
4844:
4842:
4833:
4832:
4828:
4823:Telemobiloscope
4817:
4811:
4810:
4806:
4797:
4793:
4784:
4780:
4767:
4766:
4762:
4753:
4749:
4739:
4737:
4727:
4723:
4707:
4706:
4699:Note: the word
4692:
4690:
4686:
4680:
4676:
4666:
4664:
4651:
4650:
4646:
4611:
4610:
4606:
4601:
4597:
4587:
4585:
4574:
4570:
4560:
4558:
4548:
4542:
4538:
4533:
4327:
4323:Main category:
4321:
4309:
4304:
4302:
4295:
4288:
4285:
4241:Monopulse radar
4214:
4197:secondary radar
4154:
4112:
4106:
4059:
4047:2.7–4.0 mm
4044:75–110 GHz
4031:4.0–7.5 mm
4008:Millimetre band
3998:40–300 GHz
3979:
3968:
3964:
3924:
3775:30–300 MHz
3733:Frequency range
3679:
3673:
3671:Frequency bands
3651:radio astronomy
3562:
3545:
3536:
3522:
3500:
3472:
3458:
3420:
3418:Antenna (radio)
3414:
3339:
3333:
3287:
3285:Track algorithm
3279:Main articles:
3277:
3234:
3162:
3156:
3090:
3072:
3066:
3009:
2995:
2952:
2946:
2941:
2936:
2874:
2868:
2755:on the earth’s
2708:
2706:Clutter (radar)
2690:
2677:
2671:
2640:
2638:
2635:
2634:
2624:Planck spectrum
2617:
2596:
2526:
2518:Main articles:
2516:
2474:
2472:
2470:
2468:
2466:
2464:
2448:
2444:
2435:
2431:
2425:
2421:
2403:
2399:
2381:
2377:
2371:
2367:
2352:
2348:
2342:
2338:
2332:
2328:
2316:
2312:
2310:
2306:
2298:
2295:
2294:
2293:
2286:
2276:
2271:
2242:
2236:
2202:
2198:
2193:
2184:
2180:
2179:
2177:
2169:
2163:
2159:
2154:
2152:
2149:
2148:
2128:
2124:
2122:
2119:
2118:
2093:
2089:
2087:
2079:
2073:
2069:
2064:
2062:
2059:
2058:
2034:
2030:
2028:
2025:
2024:
2007:
2003:
2001:
1998:
1997:
1980:
1976:
1974:
1971:
1970:
1953:
1949:
1947:
1944:
1943:
1926:
1922:
1920:
1917:
1916:
1882:
1878:
1876:
1872:
1863:
1859:
1850:
1846:
1844:
1841:
1840:
1834:radio astronomy
1799:
1795:
1793:
1789:
1780:
1776:
1761:
1757:
1755:
1752:
1751:
1732:
1729:
1728:
1711:
1707:
1705:
1702:
1701:
1684:
1680:
1678:
1675:
1674:
1657:
1653:
1651:
1648:
1647:
1636:radar astronomy
1600:
1592:Main articles:
1590:
1537:
1533:
1527:
1513:
1512:
1511:
1504:
1500:
1491:
1487:
1481:
1477:
1471:
1467:
1466:
1464:
1455:
1451:
1449:
1446:
1445:
1432:
1425:
1418:
1411:
1400:
1391:
1362:
1339:
1336:
1335:
1310:
1302:
1298:
1292:
1288:
1287:
1284:
1281:
1280:
1274:
1261:
1252:
1221:
1216:
1206:
1201:
1191:
1177:
1176:
1175:
1168:
1164:
1155:
1151:
1145:
1141:
1135:
1131:
1130:
1128:
1119:
1115:
1113:
1110:
1109:
1103:
1096:
988:
982:
966:
887:
869:
864:
760:
697:Popular Science
694:In April 1940,
669:
663:
556:
550:Rudolf Kühnhold
543:coastal battery
507:P.K. Oshchepkov
443:
427:Inventions Book
419:W.A.S. Butement
348:telemobiloscope
312:Alexander Popov
304:
299:
293:
221:systems, outer
203:radar astronomy
109:guided missiles
89:radial velocity
60:
59:
58:
57:
56:
53:
45:
44:
37:
24:
17:
12:
11:
5:
7146:
7136:
7135:
7130:
7125:
7120:
7115:
7110:
7105:
7100:
7095:
7090:
7085:
7080:
7063:
7062:
7060:
7059:
7054:
7048:
7045:
7044:
7042:
7041:
7036:
7031:
7025:
7023:
7019:
7018:
7016:
7015:
7004:
6999:
6994:
6989:
6984:
6979:
6974:
6969:
6964:
6959:
6954:
6948:
6946:
6942:
6941:
6939:
6938:
6933:
6928:
6923:
6918:
6912:
6910:
6909:Naval missiles
6906:
6905:
6902:
6901:
6899:
6898:
6893:
6888:
6882:
6880:
6876:
6875:
6873:
6872:
6867:
6862:
6857:
6852:
6846:
6844:
6837:
6833:
6832:
6830:
6829:
6824:
6822:List of radars
6819:
6814:
6809:
6804:
6799:
6794:
6789:
6783:
6781:
6777:
6776:
6774:
6773:
6768:
6763:
6758:
6753:
6748:
6742:
6740:
6736:
6735:
6733:
6732:
6727:
6722:
6717:
6712:
6707:
6702:
6697:
6692:
6686:
6684:
6680:
6679:
6674:
6673:
6666:
6659:
6651:
6642:
6641:
6636:
6631:
6623:
6622:External links
6620:
6619:
6618:
6612:
6599:
6562:
6541:
6532:
6527:978-1849192651
6526:
6513:
6487:
6472:
6467:978-0521821049
6466:
6447:
6441:
6418:
6412:
6399:
6393:
6381:Radar Handbook
6373:
6370:
6369:
6368:
6362:
6349:
6335:
6320:
6314:
6301:
6295:
6287:Radar handbook
6282:
6276:
6263:
6257:
6244:
6238:
6225:
6219:
6206:
6203:
6197:
6184:
6178:
6165:
6159:
6146:
6140:
6127:
6112:
6106:
6093:
6087:
6074:
6068:
6055:
6049:
6036:
6030:
6015:
6012:
6011:
6010:
6000:
5982:
5975:
5965:
5952:
5942:
5928:
5919:
5908:
5905:
5902:
5901:
5863:
5861:
5854:
5848:
5845:
5842:
5841:
5829:
5818:on 5 June 2011
5796:
5770:
5752:
5734:
5708:
5682:
5664:
5646:
5619:
5587:
5563:(March 1980).
5552:
5517:
5506:
5499:
5477:
5461:"Project Soli"
5452:
5422:
5394:
5380:
5359:
5331:
5314:portvision.com
5308:Kline, Aaron.
5300:
5278:
5260:
5239:
5221:
5191:
5164:
5142:
5120:
5098:
5071:
5053:
5040:
5010:
4997:
4988:
4970:
4957:
4944:
4937:
4919:
4900:
4891:
4866:
4852:
4826:
4804:
4791:
4778:
4773:radarworld.org
4760:
4747:
4721:
4674:
4663:on 2 June 2021
4644:
4604:
4595:
4568:
4535:
4534:
4532:
4529:
4528:
4527:
4522:
4517:
4512:
4510:Würzburg radar
4507:
4505:Chain Home Low
4498:
4496:List of radars
4492:
4491:
4487:
4486:
4481:
4476:
4471:
4465:
4464:
4460:
4459:
4454:
4449:
4444:
4439:
4434:
4429:
4424:
4419:
4413:
4412:
4408:
4407:
4405:Proximity fuze
4401:
4400:
4396:
4395:
4390:
4385:
4379:
4378:
4374:
4373:
4368:
4366:Mmwave sensing
4363:
4358:
4353:
4348:
4343:
4338:
4333:
4317:Main listing:
4315:
4314:
4300:
4284:
4281:
4280:
4279:
4270:
4269:
4268:
4258:
4253:
4248:
4243:
4238:
4233:
4228:
4223:
4221:Bistatic radar
4213:
4212:Configurations
4210:
4153:
4150:
4108:Main article:
4105:
4102:
4101:
4100:
4085:
4058:
4055:
4052:
4051:
4048:
4045:
4042:
4036:
4035:
4032:
4029:
4028:40–75 GHz
4026:
4020:
4019:
4005:
3999:
3996:
3992:
3991:
3987:
3984:
3983:24–40 GHz
3981:
3977:
3972:
3971:
3966:
3962:
3948:
3945:
3944:18–24 GHz
3942:
3936:
3935:
3932:
3929:
3928:12–18 GHz
3926:
3922:
3917:
3916:
3901:
3898:
3895:
3889:
3888:
3885:
3882:
3879:
3873:
3872:
3864:
3863:7.5–15 cm
3861:
3858:
3852:
3851:
3840:
3834:
3828:
3822:
3821:
3810:
3807:
3804:
3798:
3797:
3794:
3791:
3788:
3784:
3783:
3779:
3776:
3773:
3767:
3766:
3759:
3753:
3747:
3741:
3740:
3737:
3734:
3731:
3691:radar equation
3675:Main article:
3672:
3669:
3643:interferometry
3618:Mikoyan MiG-31
3558:Main article:
3544:
3541:
3532:Main article:
3521:
3518:
3517:
3516:
3510:
3507:
3504:
3499:
3496:
3468:Main article:
3457:
3454:
3416:Main article:
3413:
3412:Antenna design
3410:
3409:
3408:
3405:
3402:
3399:output devices
3395:
3392:matched filter
3384:
3377:
3370:
3335:Main article:
3332:
3329:
3316:
3315:
3312:
3309:
3304:
3276:
3273:
3233:
3230:
3174:Range Interval
3158:Main article:
3155:
3152:
3109:Doppler effect
3089:
3086:
3068:Main article:
3065:
3062:
3030:beat frequency
3005:Main article:
2994:
2991:
2972:speed of light
2968:time-of-flight
2950:Time of flight
2945:
2942:
2940:
2937:
2935:
2932:
2870:Main article:
2867:
2864:
2810:
2809:
2808:
2807:
2804:
2704:Main article:
2689:
2686:
2673:Main article:
2670:
2667:
2644:
2615:
2594:
2576:ultra-wideband
2515:
2512:
2511:
2510:
2506:
2499:
2469:ke : 4/3
2451:
2447:
2443:
2438:
2434:
2428:
2424:
2420:
2416:
2411:
2406:
2402:
2398:
2395:
2392:
2389:
2384:
2380:
2374:
2370:
2366:
2363:
2360:
2355:
2351:
2345:
2341:
2335:
2331:
2327:
2324:
2319:
2315:
2309:
2305:
2302:
2275:
2272:
2270:
2267:
2235:
2232:
2227:
2226:
2213:
2205:
2201:
2197:
2192:
2187:
2183:
2176:
2172:
2166:
2162:
2157:
2131:
2127:
2115:
2114:
2101:
2096:
2092:
2086:
2082:
2076:
2072:
2067:
2037:
2033:
2010:
2006:
1983:
1979:
1956:
1952:
1929:
1925:
1909:
1908:
1895:
1890:
1885:
1881:
1875:
1871:
1866:
1862:
1858:
1853:
1849:
1826:
1825:
1812:
1807:
1802:
1798:
1792:
1788:
1783:
1779:
1775:
1772:
1769:
1764:
1760:
1736:
1714:
1710:
1687:
1683:
1660:
1656:
1589:
1588:Doppler effect
1586:
1560:
1559:
1548:
1540:
1536:
1530:
1525:
1522:
1519:
1516:
1507:
1503:
1499:
1494:
1490:
1484:
1480:
1474:
1470:
1463:
1458:
1454:
1430:
1423:
1416:
1409:
1403:
1402:
1398:
1393:
1389:
1384:
1378:
1367:
1366:
1365:
1364:
1360:
1355:
1343:
1330:
1329:
1316:
1313:
1305:
1301:
1295:
1291:
1272:
1267:
1259:
1254:
1250:
1241:
1240:
1224:
1219:
1215:
1209:
1204:
1200:
1194:
1189:
1186:
1183:
1180:
1171:
1167:
1163:
1158:
1154:
1148:
1144:
1138:
1134:
1127:
1122:
1118:
1101:
1095:
1092:
1038:and sometimes
1000:Hurricane Abby
984:Main article:
981:
978:
965:
962:
954:infrared light
931:Doppler effect
868:
865:
863:
860:
815:severe weather
759:
756:
732:night fighters
689:Tizard Mission
665:Main article:
662:
659:
651:Dowding system
628:Arnold Wilkins
531:Robert M. Page
442:
439:
399:A. Hoyt Taylor
308:Heinrich Hertz
303:
300:
295:Main article:
292:
289:
281:infrared light
246:guided missile
231:meteorological
172:United Kingdom
113:motor vehicles
54:
47:
46:
38:
31:
30:
29:
28:
27:
15:
9:
6:
4:
3:
2:
7145:
7134:
7131:
7129:
7126:
7124:
7121:
7119:
7116:
7114:
7111:
7109:
7106:
7104:
7101:
7099:
7096:
7094:
7091:
7089:
7086:
7084:
7081:
7079:
7076:
7075:
7073:
7058:
7055:
7053:
7050:
7049:
7046:
7040:
7037:
7035:
7032:
7030:
7027:
7026:
7024:
7020:
7011:
7005:
7003:
7000:
6998:
6995:
6993:
6990:
6988:
6985:
6983:
6980:
6978:
6975:
6973:
6970:
6968:
6967:Ship systems:
6965:
6963:
6960:
6958:
6955:
6953:
6950:
6949:
6947:
6943:
6937:
6934:
6932:
6929:
6927:
6924:
6922:
6919:
6917:
6914:
6913:
6911:
6907:
6897:
6894:
6892:
6889:
6887:
6884:
6883:
6881:
6877:
6871:
6868:
6866:
6863:
6861:
6858:
6856:
6853:
6851:
6848:
6847:
6845:
6841:
6838:
6834:
6828:
6825:
6823:
6820:
6818:
6815:
6813:
6810:
6808:
6805:
6803:
6800:
6798:
6795:
6793:
6790:
6788:
6785:
6784:
6782:
6778:
6772:
6769:
6767:
6764:
6762:
6761:Depth charges
6759:
6757:
6754:
6752:
6749:
6747:
6744:
6743:
6741:
6737:
6731:
6728:
6726:
6723:
6721:
6718:
6716:
6713:
6711:
6708:
6706:
6703:
6701:
6698:
6696:
6693:
6691:
6690:Naval warfare
6688:
6687:
6685:
6681:
6672:
6667:
6665:
6660:
6658:
6653:
6652:
6649:
6645:
6640:
6637:
6635:
6632:
6629:
6626:
6625:
6615:
6609:
6605:
6600:
6596:
6592:
6588:
6584:
6580:
6576:
6572:
6568:
6563:
6559:
6555:
6551:
6547:
6542:
6538:
6533:
6529:
6523:
6519:
6514:
6510:
6498:
6490:
6484:
6480:
6479:
6473:
6469:
6463:
6459:
6458:
6453:
6448:
6444:
6438:
6434:
6433:
6428:
6424:
6419:
6415:
6413:9780471473787
6409:
6405:
6404:Radar signals
6400:
6396:
6394:0-07-057913-X
6390:
6383:
6382:
6376:
6375:
6365:
6359:
6355:
6350:
6348:
6344:
6340:
6336:
6333:
6329:
6325:
6321:
6317:
6311:
6307:
6302:
6298:
6292:
6288:
6283:
6279:
6273:
6269:
6264:
6260:
6254:
6250:
6245:
6241:
6235:
6231:
6226:
6222:
6216:
6212:
6207:
6204:
6200:
6194:
6190:
6185:
6181:
6175:
6171:
6166:
6162:
6156:
6152:
6147:
6143:
6137:
6133:
6128:
6125:
6121:
6117:
6113:
6109:
6103:
6099:
6094:
6090:
6084:
6080:
6075:
6071:
6065:
6061:
6056:
6052:
6046:
6042:
6037:
6033:
6027:
6023:
6018:
6017:
6008:
6006:
6001:
5998:
5994:
5991:
5989:
5983:
5980:
5976:
5973:
5971:
5966:
5963:
5959:
5958:
5953:
5951:
5949:
5943:
5940:
5936:
5933:
5929:
5926:
5925:
5920:
5917:
5916:
5911:
5910:
5898:
5895:
5887:
5884:November 2014
5877:
5876:editing guide
5871:
5867:
5862:
5853:
5852:
5839:
5838:radar / RADAR
5833:
5814:
5807:
5800:
5781:
5774:
5766:
5762:
5756:
5748:
5744:
5738:
5722:
5718:
5712:
5696:
5692:
5686:
5678:
5674:
5668:
5660:
5656:
5650:
5639:
5632:
5626:
5624:
5607:
5600:
5599:
5591:
5575:
5568:
5567:
5562:
5556:
5540:
5533:
5532:
5524:
5522:
5510:
5502:
5496:
5491:
5490:
5481:
5466:
5462:
5456:
5440:
5436:
5432:
5426:
5415:
5411:
5404:
5398:
5390:
5384:
5376:
5369:
5363:
5348:
5347:
5342:
5335:
5319:
5315:
5311:
5304:
5289:
5282:
5274:
5270:
5264:
5256:
5252:
5246:
5244:
5235:
5231:
5225:
5218:
5206:
5202:
5195:
5188:
5175:
5168:
5162:
5152:
5146:
5138:
5134:
5130:
5124:
5116:
5112:
5108:
5102:
5086:
5082:
5075:
5067:
5063:
5057:
5050:
5044:
5028:
5024:
5020:
5014:
5007:
5001:
4992:
4984:
4980:
4974:
4967:
4961:
4954:
4948:
4940:
4934:
4930:
4923:
4916:. Washington.
4915:
4911:
4904:
4895:
4880:
4876:
4870:
4862:
4856:
4840:
4836:
4830:
4824:
4814:
4808:
4802:
4801:
4795:
4789:
4788:
4782:
4774:
4770:
4764:
4757:
4751:
4736:
4732:
4725:
4717:
4711:
4704:
4702:
4685:
4678:
4662:
4658:
4654:
4648:
4639:
4634:
4630:
4626:
4622:
4618:
4614:
4608:
4599:
4583:
4579:
4572:
4556:
4555:
4547:
4540:
4536:
4526:
4525:SCR-270 radar
4523:
4521:
4518:
4516:
4513:
4511:
4508:
4506:
4502:
4499:
4497:
4494:
4493:
4489:
4488:
4485:
4482:
4480:
4477:
4475:
4472:
4470:
4467:
4466:
4462:
4461:
4458:
4455:
4453:
4450:
4448:
4445:
4443:
4440:
4438:
4435:
4433:
4430:
4428:
4425:
4423:
4420:
4418:
4415:
4414:
4410:
4409:
4406:
4403:
4402:
4398:
4397:
4394:
4391:
4389:
4386:
4384:
4381:
4380:
4376:
4375:
4372:
4369:
4367:
4364:
4362:
4359:
4357:
4354:
4352:
4349:
4347:
4344:
4342:
4339:
4337:
4336:Radar imaging
4334:
4332:
4329:
4328:
4326:
4320:
4312:
4301:
4298:
4292:
4287:
4278:
4274:
4271:
4267:
4264:
4263:
4262:
4259:
4257:
4256:Pulse-doppler
4254:
4252:
4249:
4247:
4246:Passive radar
4244:
4242:
4239:
4237:
4234:
4232:
4231:Doppler radar
4229:
4227:
4224:
4222:
4219:
4218:
4217:
4208:
4206:
4202:
4198:
4194:
4193:primary radar
4190:
4186:
4182:
4176:
4174:
4170:
4166:
4165:article 1.100
4162:
4158:
4149:
4147:
4142:
4139:, leading to
4138:
4134:
4131:
4127:
4123:
4121:
4117:
4111:
4098:
4094:
4090:
4086:
4083:
4079:
4075:
4071:
4067:
4066:
4065:
4063:
4049:
4046:
4043:
4041:
4038:
4037:
4033:
4030:
4027:
4025:
4022:
4021:
4017:
4013:
4009:
4006:
4004:
4001:1.0–7.5
4000:
3997:
3994:
3993:
3988:
3985:
3982:
3980:
3974:
3973:
3960:
3956:
3953:
3949:
3946:
3943:
3941:
3938:
3937:
3933:
3930:
3927:
3925:
3919:
3918:
3913:
3909:
3905:
3902:
3899:
3897:8–12 GHz
3896:
3894:
3891:
3890:
3886:
3883:
3880:
3878:
3875:
3874:
3870:
3865:
3862:
3859:
3857:
3854:
3853:
3849:
3845:
3841:
3839:
3835:
3833:
3829:
3827:
3824:
3823:
3819:
3815:
3811:
3808:
3805:
3803:
3800:
3799:
3795:
3792:
3789:
3786:
3785:
3780:
3777:
3774:
3772:
3769:
3768:
3764:
3760:
3758:
3754:
3752:
3748:
3746:
3743:
3742:
3738:
3735:
3732:
3729:
3728:
3725:
3720:
3718:
3714:
3709:
3707:
3703:
3698:
3696:
3692:
3686:
3684:
3678:
3668:
3666:
3662:
3658:
3656:
3652:
3648:
3644:
3641:Phased-array
3639:
3637:
3633:
3630:
3626:
3623:
3619:
3615:
3610:
3606:
3603:
3601:
3598:
3594:
3590:
3586:
3582:
3577:
3575:
3569:
3567:
3561:
3553:
3549:
3540:
3535:
3526:
3514:
3511:
3508:
3505:
3502:
3501:
3498:Types of scan
3495:
3492:
3491:Pulse-Doppler
3489:
3483:
3481:
3477:
3471:
3462:
3453:
3451:
3446:
3441:
3437:
3432:
3424:
3419:
3406:
3403:
3400:
3396:
3393:
3389:
3385:
3382:
3378:
3375:
3371:
3368:
3364:
3360:
3356:
3352:
3351:
3350:
3343:
3338:
3328:
3326:
3325:radar tracker
3320:
3313:
3310:
3308:
3305:
3303:
3300:
3299:
3298:
3295:
3291:
3286:
3282:
3281:Radar tracker
3272:
3270:
3266:
3262:
3258:
3254:
3250:
3246:
3242:
3238:
3229:
3226:
3222:
3217:
3213:
3209:
3204:
3202:
3197:
3196:weather radar
3192:
3189:
3180:
3175:
3171:
3166:
3161:
3151:
3149:
3145:
3141:
3135:
3133:
3128:
3126:
3122:
3121:weather radar
3118:
3114:
3113:Doppler radar
3110:
3105:
3103:
3099:
3098:grease pencil
3094:
3085:
3081:
3078:
3071:
3061:
3057:
3055:
3051:
3047:
3043:
3038:
3033:
3031:
3026:
3022:
3018:
3013:
3008:
2999:
2990:
2988:
2987:nautical mile
2984:
2979:
2975:
2973:
2969:
2965:
2956:
2951:
2931:
2929:
2925:
2921:
2917:
2912:
2907:
2905:
2901:
2897:
2893:
2892:line of sight
2889:
2883:
2880:
2873:
2863:
2860:
2856:
2852:
2848:
2844:
2839:
2837:
2833:
2829:
2827:
2823:
2819:
2815:
2805:
2802:
2801:
2800:
2799:
2798:
2796:
2791:
2789:
2785:
2779:
2777:
2773:
2768:
2766:
2762:
2758:
2757:magnetosphere
2754:
2750:
2746:
2745:space weather
2742:
2738:
2734:
2730:
2726:
2722:
2718:
2717:precipitation
2714:
2707:
2699:
2694:
2685:
2683:
2676:
2666:
2664:
2660:
2642:
2632:
2627:
2625:
2621:
2614:
2610:
2606:
2602:
2599:
2593:
2589:
2588:thermal noise
2583:
2581:
2577:
2572:
2568:
2567:flicker noise
2564:
2560:
2558:
2552:
2550:
2546:
2542:
2538:
2534:
2529:
2525:
2524:Noise (radio)
2521:
2507:
2504:
2500:
2497:
2496:
2495:
2492:
2490:
2486:
2485:radar horizon
2482:
2465:Where :
2449:
2445:
2441:
2436:
2432:
2426:
2422:
2418:
2414:
2404:
2400:
2393:
2390:
2387:
2382:
2378:
2372:
2368:
2364:
2361:
2358:
2353:
2343:
2339:
2333:
2329:
2322:
2317:
2313:
2307:
2303:
2300:
2290:
2285:
2281:
2266:
2264:
2260:
2256:
2251:
2247:
2241:
2231:
2211:
2203:
2199:
2195:
2190:
2185:
2181:
2174:
2164:
2160:
2147:
2146:
2145:
2129:
2125:
2099:
2094:
2090:
2084:
2074:
2070:
2057:
2056:
2055:
2053:
2050:, called the
2035:
2031:
2008:
2004:
1981:
1977:
1954:
1950:
1927:
1923:
1913:
1893:
1888:
1883:
1879:
1873:
1869:
1864:
1860:
1856:
1851:
1847:
1839:
1838:
1837:
1835:
1831:
1810:
1805:
1800:
1796:
1790:
1786:
1781:
1777:
1773:
1770:
1767:
1762:
1758:
1750:
1749:
1748:
1734:
1712:
1708:
1685:
1681:
1658:
1654:
1644:
1640:
1637:
1633:
1632:weather radar
1629:
1625:
1620:
1618:
1609:
1604:
1599:
1595:
1594:Doppler radar
1585:
1583:
1579:
1575:
1570:
1568:
1563:
1546:
1538:
1534:
1528:
1520:
1517:
1505:
1501:
1497:
1492:
1488:
1482:
1478:
1472:
1468:
1461:
1456:
1452:
1444:
1443:
1442:
1440:
1436:
1429:
1422:
1419:and the term
1415:
1408:
1397:
1394:
1388:
1385:
1382:
1379:
1376:
1372:
1369:
1368:
1359:
1356:
1341:
1334:
1333:
1332:
1331:
1314:
1311:
1303:
1299:
1293:
1289:
1278:
1271:
1268:
1265:
1258:
1255:
1249:
1246:
1245:
1244:
1222:
1217:
1213:
1207:
1202:
1198:
1192:
1184:
1181:
1169:
1165:
1161:
1156:
1152:
1146:
1142:
1136:
1132:
1125:
1120:
1116:
1108:
1107:
1106:
1104:
1091:
1089:
1085:
1081:
1077:
1072:
1068:
1063:
1061:
1057:
1053:
1047:
1045:
1041:
1037:
1034:, containing
1033:
1029:
1025:
1021:
1017:
1013:
1009:
1001:
997:
996:weather radar
992:
987:
977:
975:
971:
961:
959:
955:
951:
950:visible light
945:
943:
939:
934:
932:
928:
924:
920:
916:
912:
908:
904:
900:
899:radar signals
896:
892:
886:
878:
873:
859:
857:
853:
849:
844:
840:
839:Earth's crust
836:
832:
828:
827:winter storms
824:
820:
819:thunderstorms
816:
812:
808:
807:precipitation
803:
801:
796:
795:Marine radars
792:
789:
785:
781:
777:
772:
764:
755:
753:
749:
745:
741:
737:
733:
728:
726:
722:
718:
714:
710:
705:
704:
699:
698:
692:
690:
686:
678:
673:
668:
658:
654:
652:
648:
644:
640:
639:Bawdsey Manor
636:
629:
624:
617:
612:
608:
606:
602:
598:
594:
589:
581:
576:
572:
570:
566:
560:
555:
552:and the firm
551:
547:
544:
540:
536:
532:
527:
524:
520:
516:
512:
508:
503:
501:
500:
495:
491:
486:
484:
480:
476:
472:
468:
464:
460:
452:
447:
438:
436:
432:
428:
424:
420:
415:
413:
409:
404:
400:
396:
395:Potomac River
391:
389:
385:
381:
377:
373:
369:
364:
359:
357:
353:
349:
344:
339:
337:
333:
329:
325:
321:
317:
313:
309:
298:
288:
286:
282:
278:
274:
269:
267:
263:
259:
255:
251:
247:
243:
239:
235:
234:precipitation
232:
228:
224:
220:
216:
215:marine radars
212:
208:
204:
199:
197:
193:
189:
185:
181:
177:
173:
169:
165:
161:
156:
153:
149:
145:
141:
137:
133:
129:
124:
122:
118:
114:
110:
106:
102:
98:
94:
90:
86:
82:
78:
74:
73:
68:
64:
51:
42:
35:
26:
22:
7057:Naval combat
7028:
7013:}}
7007:{{
7001:
6986:
6966:
6816:
6806:
6724:
6719:
6643:
6603:
6573:(1): 32–41.
6570:
6566:
6549:
6545:
6536:
6517:
6477:
6456:
6431:
6427:Petre Stoica
6403:
6380:
6353:
6338:
6323:
6305:
6286:
6267:
6248:
6229:
6210:
6188:
6169:
6150:
6131:
6115:
6097:
6078:
6059:
6040:
6021:
6003:
5987:
5978:
5968:
5955:
5947:
5922:
5913:
5890:
5881:
5869:
5847:Bibliography
5837:
5832:
5820:. Retrieved
5813:the original
5799:
5787:. Retrieved
5773:
5764:
5755:
5746:
5737:
5725:. Retrieved
5711:
5701:11 September
5699:. Retrieved
5695:the original
5685:
5677:the original
5667:
5659:the original
5649:
5638:the original
5610:. Retrieved
5597:
5590:
5578:. Retrieved
5565:
5555:
5543:. Retrieved
5530:
5509:
5488:
5480:
5468:. Retrieved
5464:
5455:
5443:. Retrieved
5439:the original
5434:
5425:
5409:
5397:
5383:
5374:
5362:
5350:. Retrieved
5344:
5334:
5322:. Retrieved
5318:the original
5313:
5303:
5291:. Retrieved
5281:
5273:Daily Record
5272:
5263:
5254:
5233:
5224:
5215:
5208:. Retrieved
5204:
5194:
5185:
5178:. Retrieved
5167:
5160:
5145:
5137:the original
5133:Media Centre
5132:
5123:
5115:the original
5110:
5101:
5089:. Retrieved
5085:the original
5074:
5065:
5056:
5048:
5043:
5031:. Retrieved
5027:the original
5022:
5013:
5005:
5000:
4991:
4982:
4973:
4965:
4960:
4952:
4947:
4928:
4922:
4913:
4903:
4894:
4882:. Retrieved
4878:
4869:
4855:
4843:. Retrieved
4839:the original
4829:
4822:
4807:
4799:
4794:
4786:
4781:
4772:
4763:
4755:
4750:
4738:. Retrieved
4734:
4724:
4700:
4698:
4691:. Retrieved
4677:
4665:. Retrieved
4661:the original
4656:
4647:
4620:
4616:
4607:
4598:
4586:. Retrieved
4582:the original
4571:
4559:. Retrieved
4553:
4544:ITU (2020).
4539:
4215:
4188:
4184:
4178:
4164:
4160:
4156:
4155:
4124:
4113:
4082:pulsed power
4060:
3959:water vapour
3954:
3908:marine radar
3881:4–8 GHz
3860:2–4 GHz
3844:surveillance
3723:
3713:broadcasting
3710:
3699:
3687:
3680:
3659:
3640:
3611:
3607:
3604:
3600:surveillance
3581:Mammut radar
3578:
3574:antenna gain
3570:
3566:phased array
3563:
3560:Phased array
3552:Phased array
3543:Phased array
3537:
3484:
3479:
3473:
3450:a small part
3440:right angles
3433:
3429:
3348:
3321:
3317:
3296:
3292:
3288:
3235:
3205:
3193:
3184:
3179:bed of nails
3178:
3173:
3170:Range Sample
3169:
3136:
3129:
3106:
3091:
3082:
3073:
3058:
3034:
3029:
3014:
3010:
2982:
2980:
2976:
2961:
2944:Transit time
2928:polarization
2908:
2903:
2895:
2884:
2875:
2840:
2834:, a form of
2830:
2811:
2792:
2780:
2769:
2709:
2678:
2669:Interference
2628:
2612:
2608:
2604:
2600:
2597:
2591:
2584:
2561:
2557:noise figure
2553:
2530:
2527:
2493:
2478:
2280:Beam forming
2250:polarization
2243:
2234:Polarization
2228:
2116:
1914:
1910:
1836:as follows:
1827:
1645:
1641:
1621:
1613:
1573:
1571:
1564:
1561:
1438:
1434:
1427:
1420:
1413:
1406:
1404:
1395:
1386:
1380:
1370:
1357:
1269:
1256:
1247:
1242:
1099:
1097:
1064:
1048:
1005:
974:illumination
973:
967:
964:Illumination
946:
935:
922:
898:
888:
867:Radar signal
804:
793:
773:
769:
758:Applications
750:used by the
729:
701:
695:
693:
682:
655:
635:Air Ministry
632:
601:Hugh Dowding
585:
582:and his team
567:team led by
565:Air Ministry
546:searchlights
528:
504:
498:
487:
479:Soviet Union
456:
426:
416:
403:Leo C. Young
392:
360:
347:
340:
305:
270:
236:monitoring,
200:
187:
175:
164:World War II
157:
125:
70:
62:
61:
25:
6957:Rangekeeper
6771:Naval mines
6725:Historical:
6505:|work=
6024:. R. Hale.
5962:Radar World
5930:Ekco Radar
4955:, Jan. 1931
4845:24 February
4447:Radar tower
4399:Application
4377:Definitions
4236:Fm-cw radar
4152:Regulations
4137:hygroscopic
4099:techniques.
4016:helicopters
3614:B-1B Lancer
3355:transmitter
3331:Engineering
3127:over time.
3042:transponder
2911:solid angle
2725:dust storms
2549:noise floor
2533:noise floor
1080:diffraction
895:radio waves
893:that emits
891:transmitter
877:Barker code
675:East Coast
557: [
457:Before the
128:transmitter
67:radio waves
7072:Categories
6945:Historical
6452:Guang Gong
6041:Radar Days
5907:References
5868:" section
5727:8 February
5612:2 December
5580:2 December
5561:Elkins, TJ
5545:2 December
5470:29 October
5445:29 October
5324:1 February
5176:. BBC News
4884:1 December
4588:8 November
4501:Chain Home
4351:Wave radar
4141:hydrolysis
4062:Modulators
4057:Modulators
4012:power line
3906:guidance,
3480:radar lock
3221:medium PRF
3102:slide rule
3080:antennas.
2983:radar mile
2851:refraction
2753:solar wind
2739:caused by
2737:ionosphere
2721:hail spike
2571:heterodyne
2563:Shot noise
2278:See also:
1608:wavelength
1606:Change of
1098:The power
1060:resonances
998:image (of
980:Reflection
862:Principles
843:radar guns
831:Geologists
677:Chain Home
643:Chain Home
616:Chain Home
431:Chain Home
423:breadboard
368:ionosphere
332:Baltic Sea
318:school in
227:rendezvous
140:microwaves
130:producing
105:spacecraft
7002:Navboxes:
6812:Nike Zeus
6756:Torpedoes
6507:ignored (
6497:cite book
5977:Pub 1310
5921:Buderi, "
5789:12 August
5210:9 October
5180:16 August
5151:GB 593017
4740:9 January
4520:H2S radar
4175:(RR) as:
4120:klystrons
4078:magnetron
4074:thyratron
3730:Band name
3629:AN/APG-77
3476:parabolic
3374:waveguide
3367:modulator
3363:magnetron
3255:targets,
3119:systems (
3025:sine wave
2900:sidelobes
2772:waveguide
2743:or other
2663:coherence
2545:Detection
2419:−
2401:θ
2191:×
1870:×
1787:×
1774:×
1578:multipath
1521:π
1498:σ
1342:λ
1315:π
1300:λ
1185:π
1162:σ
1036:resistive
927:frequency
907:scattered
903:reflected
897:known as
823:tornadoes
588:death ray
502:in 1935.
499:Normandie
380:shortwave
372:lightning
361:In 1915,
356:Rotterdam
320:Kronstadt
229:systems,
192:anacronym
152:processor
77:direction
7083:Avionics
6860:AN/SPY-3
6855:AN/SPY-1
6595:16437755
6454:(2005).
6429:(2012).
6421:Hao He;
5993:Archived
5974:". 2002.
5935:Archived
5822:18 March
5414:Archived
5293:24 March
5033:28 April
5023:kret.com
4813:GB 13170
4710:cite web
4561:24 March
4432:Klystron
4411:Hardware
4283:See also
4130:silicate
4126:Coolanol
4093:klystron
4089:coherent
3591:and the
3445:rotating
3388:receiver
3381:duplexer
3359:klystron
2603:, where
1582:pathloss
1437:, where
1040:magnetic
1022:or in a
915:seawater
817:such as
776:aviation
519:Gneiss-2
268:levels.
160:military
148:receiver
97:aircraft
7022:Related
6879:Optical
6836:Sensors
6739:Weapons
6683:General
6575:Bibcode
6423:Jian Li
6014:General
5389:"Terma"
5377:. 2007.
4693:2 March
4625:Bibcode
4203:or the
4167:of the
4159:(also:
4110:Coolant
4104:Coolant
3912:airport
3904:Missile
3871:tasks.
3809:0.3–1 m
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