141:
22:
480:
The modulation depth of each 90 Hz and 150 Hz signal changes according to the deviation of the aircraft from the correct position for the aircraft to touchdown on the threshold. The difference between the two signal modulation depths is zero when the aircraft is on the correct course and
459:
An aircraft with an on-board ILS receiver within the capture area of an ILS, (glideslope and localizer range), will detect varying depths of modulation according to the aircraft's position within that airspace, providing accurate positional information about the progress to the threshold.
455:
airspace. This modulation method differs from internal modulation methods inside most other radio transmitters in that the phases and powers of the two individual signals mix within airspace, rather than in a modulator.
468:
The ILS uses two radio frequencies, one for each ground station (about 110 MHz for LOC and 330 MHz for the GS), to transmit two amplitude-modulated signals (90 Hz and 150 Hz), along the
423:
387:
94:
498:
486:
448:
66:
447:(ILS) that incorporates the use of multiple antennas fed with various radio frequency powers and phases to create different
477:. It is this signal that is projected up from the runway which an aircraft employing an instrument approach uses to land.
416:
332:
73:
311:
113:
43:
51:
489:), produces no deviation from the middle indication of the instrument's needle within the cockpit of the aircraft.
205:
80:
392:
306:
278:
245:
220:
172:
409:
47:
62:
210:
362:
182:
518:
503:
444:
235:
372:
255:
32:
191:
452:
269:
148:
36:
382:
377:
215:
200:
87:
367:
301:
440:
225:
162:
157:
8:
250:
283:
260:
240:
230:
357:
352:
167:
292:
512:
140:
397:
337:
316:
132:
482:
470:
342:
21:
474:
129:
463:
347:
485:on approach to the runway—i.e. No difference (zero
510:
417:
473:(GS) and the course (LOC) trajectories into
50:. Unsourced material may be challenged and
464:Method used to determine aircraft position
424:
410:
114:Learn how and when to remove this message
511:
499:Difference in the Depth of Modulation
48:adding citations to reliable sources
15:
13:
14:
530:
139:
20:
1:
7:
492:
10:
535:
451:within various volumes of
445:instrument landing systems
333:Capacity-approaching codes
504:Instrument Landing System
270:Hierarchical modulation
449:depths of modulation
441:amplitude modulation
44:improve this article
443:technique used in
192:Digital modulation
63:"Space modulation"
453:three-dimensional
434:
433:
149:Analog modulation
124:
123:
116:
98:
526:
519:Radio navigation
437:Space modulation
426:
419:
412:
143:
126:
125:
119:
112:
108:
105:
99:
97:
56:
24:
16:
534:
533:
529:
528:
527:
525:
524:
523:
509:
508:
495:
466:
430:
293:Spread spectrum
120:
109:
103:
100:
57:
55:
41:
25:
12:
11:
5:
532:
522:
521:
507:
506:
501:
494:
491:
465:
462:
432:
431:
429:
428:
421:
414:
406:
403:
402:
401:
400:
395:
390:
385:
380:
375:
370:
365:
360:
355:
350:
345:
340:
335:
327:
326:
322:
321:
320:
319:
314:
309:
304:
296:
295:
289:
288:
287:
286:
281:
273:
272:
266:
265:
264:
263:
258:
253:
248:
243:
238:
233:
228:
223:
218:
213:
208:
203:
195:
194:
188:
187:
186:
185:
180:
175:
170:
165:
160:
152:
151:
145:
144:
136:
135:
122:
121:
28:
26:
19:
9:
6:
4:
3:
2:
531:
520:
517:
516:
514:
505:
502:
500:
497:
496:
490:
488:
484:
478:
476:
472:
461:
457:
454:
450:
446:
442:
438:
427:
422:
420:
415:
413:
408:
407:
405:
404:
399:
396:
394:
391:
389:
386:
384:
381:
379:
376:
374:
371:
369:
366:
364:
361:
359:
356:
354:
351:
349:
346:
344:
341:
339:
336:
334:
331:
330:
329:
328:
324:
323:
318:
315:
313:
310:
308:
305:
303:
300:
299:
298:
297:
294:
291:
290:
285:
282:
280:
277:
276:
275:
274:
271:
268:
267:
262:
259:
257:
254:
252:
249:
247:
244:
242:
239:
237:
234:
232:
229:
227:
224:
222:
219:
217:
214:
212:
209:
207:
204:
202:
199:
198:
197:
196:
193:
190:
189:
184:
181:
179:
176:
174:
171:
169:
166:
164:
161:
159:
156:
155:
154:
153:
150:
147:
146:
142:
138:
137:
134:
131:
128:
127:
118:
115:
107:
96:
93:
89:
86:
82:
79:
75:
72:
68:
65: –
64:
60:
59:Find sources:
53:
49:
45:
39:
38:
34:
29:This article
27:
23:
18:
17:
479:
467:
458:
436:
435:
398:Multiplexing
338:Demodulation
177:
110:
101:
91:
84:
77:
70:
58:
42:Please help
30:
439:is a radio
343:Line coding
133:modulation
74:newspapers
483:glidepath
471:glidepath
104:June 2013
31:does not
513:Category
493:See also
475:airspace
325:See also
130:Passband
88:scholar
52:removed
37:sources
251:SC-FDE
90:
83:
76:
69:
61:
348:Modem
95:JSTOR
81:books
388:OFDM
317:THSS
312:FHSS
307:DSSS
221:MFSK
206:APSK
67:news
35:any
33:cite
487:DDM
393:FDM
383:ΔΣM
378:PWM
373:PDM
368:PCM
363:PAM
358:PoM
353:AnM
302:CSS
284:WDM
279:QAM
261:WDM
256:TCM
246:QAM
241:PSK
236:PPM
231:OOK
226:MSK
216:FSK
211:CPM
201:ASK
183:SSB
173:QAM
46:by
515::
178:SM
168:PM
163:FM
158:AM
425:e
418:t
411:v
117:)
111:(
106:)
102:(
92:·
85:·
78:·
71:·
54:.
40:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
