GEOGRAPHIC ADDRESSING BY INTERROGATION FOR CONTROLLING AIRPORT GROUND TRAFFIC

摘要

1424900 Radar BENDIX CORP 20 Dec 1973 [22 Dec 1972] 59114/73 Heading H4D A system is described for geographic addressing of an individual portion D, Fig. 1, inside a field of interest 10, which utilizes a transponder system wherein a transponder receiving a first message may be suppressed for a predetermined period of time thereafter, and wherein an unsuppressed transponder responds to a second received message. First means 14 are provided for transmitting the first message over the field of interest except along a first relatively narrow beam 20, and second means 16 are provided for effectively transmitting the second message along a second relatively narrow beam 22. The intersection of the two beams defines the portion D. In application to the location and control of grounded aircraft at an airport the transponders are standard air traffic control transponders installed on the aircraft. The first and second means 14, 16 are air traffic control radar beacon system (ATCRBS) interrogators operating cooperatively. The interrogator 14 first sends a pulse P1SP1/SP on a broad beam, so that it is received by all transponders within the area 10. Then, after 2 micro-seconds, it sends a suppression pulse P2SP1/SP on a similar broad beam but which has a notch corresponding to the narrow beam 20. This suppresses reception by all transponders except those within said beam, for a period of 35 Π10 microseconds. After a suitable interval during the said suppression period, the interrogator 16 sends a pulse triad P1, P2, P3. The pulse P1 is sent on a broad beam, and the said interval is determined by the consideration that no unsuppressed transponder within the beam 20 must make a false response. The pulse P2 follows after 2 microseconds and is sent on a broad beam which has a notch corresponding to the narrow beam 22. This suppresses reception by all remaining transponders except those within the area D. The pulse P3 is sent 8 microseconds after the pulse P1, and causes a response by any transponder within the area D, giving particulars of the aircraft concerned. As shown in Fig. 3, the interrogator 14 comprises a clock 30, an encoder 32 an interrogating pulse transmitter 34, and an aerial system 40. It also comprises a link transmitter 38 and a directional aerial 40, whereby command pulses Pa, Pb are sent to the interrogator 16. This comprises a receiver 44 for said command pulses, a decoder/ encoder 42 an interrogating pulse transmitter 46, and an aerial system 50. The location of the responding transponder is determinable from the azimuth angles of the aerial systems 36, 50.