Method for reducing transmit power for traffic alert and collision avoidance systems and airborne collision avoidance systems
First Claim
1. In an aircraft having a collision avoidance system, a method for interrogating aircraft at extended ranges and for increasing interrogations in crowded airspace, said method comprising:
- identifying aircraft within a surveillance volume in response to a full power broadcast of a Mode S interrogation;
classifying each identified aircraft as either traffic or intruder;
maintaining a track for each aircraft;
reducing the transmit power of a next Mode S interrogation directed to one of said aircraft;
determining whether said one of said aircraft responds to said reduced power transmission of said Mode S interrogation;
if said one of said aircraft responds to said Mode S interrogation, repeating said maintaining, reducing and determining steps; and
if said one of said aircraft fails to respond to said Mode S interrogation, increasing said transmit power of a next Mode S interrogation directed to said one of said aircraft.
1 Assignment
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Accused Products
Abstract
The present invention provides a method for efficient use of the transmit power of a Traffic Alert Collision Avoidance System (TCAS) that allows enhanced surveillance range and limits radio frequency (RF) interference in crowded airspace. The method reduces power density in crowded airspace by modifying Mode S, Mode A and Mode C interrogations. During Mode S broadcasts, tracking interrogation power is reduced as a function of range. Further transmit power reduction is achieved by broadcasting a variable power density whisper-shout interrogation technique for Mode A/C aircraft when garbling is detected. If garbling is observed during a medium whisper-shout interrogation sequence, the method of the present invention attempts to clear the garbling by using focused high-density whisper-shout steps but only in the ranges where garbling was detected. Formation members can account for other formation members that are TCAS equipped using a special E-TCAS Broadcast Interrogation. The presence of other E-TCAS will be used in the RF interference limiting calculations. Aircraft flying in formation further minimize broadcast power by sharing information between the formation leader and formation aircraft.
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Citations
43 Claims
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1. In an aircraft having a collision avoidance system, a method for interrogating aircraft at extended ranges and for increasing interrogations in crowded airspace, said method comprising:
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identifying aircraft within a surveillance volume in response to a full power broadcast of a Mode S interrogation;
classifying each identified aircraft as either traffic or intruder;
maintaining a track for each aircraft;
reducing the transmit power of a next Mode S interrogation directed to one of said aircraft;
determining whether said one of said aircraft responds to said reduced power transmission of said Mode S interrogation;
if said one of said aircraft responds to said Mode S interrogation, repeating said maintaining, reducing and determining steps; and
if said one of said aircraft fails to respond to said Mode S interrogation, increasing said transmit power of a next Mode S interrogation directed to said one of said aircraft. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 15, 16, 17, 19, 20, 21)
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14. A method for conducting surveillance of an airspace surrounding an aircraft to track Mode S aircraft, said method comprising the steps of:
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tracking Mode S aircraft within said surveillance volume with a progressively reduced transmission power of said Mode S tracking interrogation as a function of range; and
adjusting the transmission power of said Mode S tracking interrogation to track said Mode S aircraft in response to relative motion of said aircraft and said Mode S aircraft to minimize transmission power over time.
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18. A method for conducting surveillance of an airspace surrounding an aircraft to track Mode A/C aircraft and to minimize transmission power over time, said method comprising the steps of:
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transmitting a first whisper-shout sequence to track Mode A/C aircraft in said surveillance volume, said first whisper-shout sequence comprising a plurality of interrogation steps, each of said plurality of interrogation steps having an associated transmit power level sufficient to interrogate Mode A/C aircraft within a portion of said surveillance volume;
adjusting a receiver trigger level to detect replies to said whisper-shout sequence, said trigger level adjusted to correspond to the interrogation power level; and
in response to detection of garbling in one of said portions of said surveillance volume, transmitting a second whisper-shout sequence, said second whisper-shout sequence comprising a plurality of steps for detecting Mode A/C aircraft within a specific portion of said surveillance volume where said garbling is detected.
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22. A method for conducting surveillance of an airspace surrounding an aircraft to track Mode S and Mode A/C aircraft and to minimize transmission power over time, said method comprising the steps of:
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tracking Mode S aircraft within said surveillance volume with a progressively reduced transmission power of said Mode S tracking interrogation as a function of range;
adjusting the transmission power of said Mode S tracking interrogation to track said Mode S aircraft in response to relative motion of said aircraft and said Mode S aircraft to minimize transmission power over time;
transmitting a first whisper-shout sequence to track Mode A/C aircraft in said surveillance volume, said first whisper-shout sequence comprising a plurality of interrogation steps, each of said plurality of interrogation steps having an associated transmit power level sufficient to interrogate Mode A/C aircraft within a portion of said surveillance volume;
adjusting a receiver trigger level to detect replies to said whisper-shout sequence, said trigger level adjusted to correspond to the interrogation power level; and
in response to detection of garbling in one of said portions of said surveillance volume, transmitting a second whisper-shout sequence, said second whisper-shout sequence comprising a plurality of steps for detecting Mode A/C aircraft within a specific portion of said surveillance volume where said garbling is detected. - View Dependent Claims (23, 24, 25, 26, 27, 29, 30, 31, 32, 33, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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28. A method for conducting surveillance of Mode S, Mode A and Mode C aircraft in an airspace surrounding a formation of aircraft, said formation having a formation leader and at least one formation member, said method comprising the steps of:
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inhibiting Mode S interrogation and whisper-shout interrogations from said at least one formation member;
performing passive surveillance by said at least one formation member to track the position of said formation leader and other passive intruders performing active interrogation by said formation leader;
transferring, from a formation leader to said at least one formation member, information relating to Mode S, Mode A and Mode C aircraft in said airspace.
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34. A low power method for interrogating Mode S traffic by a reference aircraft comprising the steps of:
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A) transmitting an initial tracking interrogation at maximum power (Pmax) to detect traffic within a surveillance volume surrounding said reference aircraft;
B) after the track is established, transmitting subsequent tracking interrogations at successively reduced in power until either the intruder does not reply or a minimum power limit (Plim) is reached;
C) if said Mode S traffic does not reply to said tracking interrogation, transmitting a retry tracking interrogation at a higher power level;
D) transmitting an interrogation following said retry tracking interrogation which will be at an intermediate power level; and
E) repeating steps B, C and D until said traffic is no longer within said surveillance volume.
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Specification