Abstract: A super resolution processor/receiver to discriminate superimposed secondary surveillance radar (Mode S, Mode A/C) replies and squitter that uses frequency-domain analysis to suppress interference between replies. In particular, the processor/receiver uses a spectral super-resolution method to estimate carriers of reply signals (every reply has a carrier that could be slightly different from the others). These frequency analyses, applied with particular timing referring to the signal that effectively carried the information, allow to estimate the information on SSR Mode S/Mode A/C replies.

Abstract: A super resolution processor/receiver to discriminate superimposed secondary surveillance radar (Mode S, Mode A/C) replies and squitter that uses frequency-domain analysis to suppress interference between replies. In particular, the processor/receiver uses a spectral super-resolution method to estimate carriers of reply signals (every reply has a carrier that could be slightly different from the others). These frequency analyses, applied with particular timing referring to the signal that effectively carried the information, allow to estimate the information on SSR Mode S/Mode A/C replies.

Abstract: An algorithm for improved tracking of Air Traffic Control Radar Beacon System transponders is disclosed. The algorithm can be combined with a system that includes an interrogator which transmits an interrogation signal to an associated vehicle transponder at a first frequency, preferably 1030 MHZ in accordance with FAA regulations, and a receiver array which receives the transponder reply signal transmitted by the transponder at a second frequency, preferably 1090 MHZ in accordance with FAA regulations. An angle of arrival processor calculates an angle of the received reply signal, and a position processor calculates the vehicle position based on at least the received angle data.

Abstract: A method is provided for controlling transponder replies to Mode-S interrogation signals. The method includes receiving Mode-S signals containing P5 and P6 pulses each having certain amplitudes. Each P6 pulse contains a sync phase reversal (SPR) signal followed by a data segment containing Mode-S data. The P5 pulse is asynchronous with respect to the P6 pulse and is timed to overlay the SPR signal. The method includes, analyzing each P5 and corresponding P6 pulse, identifying the SPR signal correctly in the received Mode-S signals in which the amplitude of the P6 pulse is at least 12 dB greater than the amplitude of the P5 pulse and in no more than 2% of the received Mode-S signals in which the amplitude of the P6 pulse is at least 3 dB less than the amplitude of the P5 pulse, and replying to the Mode-S signals where the SPR signal is correctly identified.

Abstract: A Mode-S transponder is provided for detecting synchronization phase reversal (SPR) signal. The transponder includes a receiver for receiving a Mode-S signal that contains a P6 pulse having a Mode-S data segment and an SPR signal therein. The transponder also includes a phrase detector that detects a phase change between first and second states in the received Mode-S signal. The phase detector includes an SPR qualifier that determine whether, following a state change, the Mode-S signal remains at one of the first and second states for at least a predetermined minimum time sufficient to qualify as a detector enable signal.

Abstract: An embedded digitization system which enables a military platform to receive, transmit and process a variety of types of information for a variety of purposes. The system includes a mission processing capability, a digital message communications capability, a time and position location and navigation capability, a weapons delivery system aim and shoot capability, a sensor input processing capability, a user interface capability, and an input/output processing capability. The system exchanges information through digital message communications with other systems in a theater of operation. Information exchanged and processed by the system includes command and control information, situational information, intelligence information, mission information and host platform information.

Abstract: A system and method for measuring and predicting information on the position of approaching aircraft are disclosed. The system features a processor, an interrogating antenna, a receiving antenna, and a data link. The processor schedules interrogations and suppression pulses. Both of the antennas and the data link are in signal communication with the processor. The interrogating antenna transmits interrogations to a plurality of approaching aircraft. At least some of the interrogations include suppression pulses. The receiving antenna comprises at least three fixed, broad azimuth, array elements. The receiving antenna receives replies from each of the plurality of approaching aircraft and communicates the replies to the processor. The processor determines a state for each of the plurality of approaching aircraft based on the replies. The data link communicates information on the state of each of the plurality of approaching aircraft from the processor.

Abstract: A method of processing reply signals received in response to an interrogation by a secondary surveillance radar system. The method includes the steps of receiving a reply signal from each of a plurality of targets, and enabling each of a plurality of target mode blocks having a predefined mode to select from the reply signals. The method further includes the step of correlating the selected reply signal to the target mode block that selected same.

Abstract: A positive stop capping system is provided for sealing an inkjet printhead in an inkjet printing mechanism during periods of printing inactivity. A positive stop or brace is provided in a cavity defined under a cap cover skin, with the skin also forming a sealing lip which surrounds ink-ejecting nozzles of the printhead when sealed. The flexible skin supporting the lip deflects into the cavity toward the brace when the cap is moved into a sealing position, in some cases contacting the brace, and in other cases, compressing the brace. An inkjet printing mechanism having the positive stop capping system and method of capping using this system are also provided.

Abstract: An aircraft system and method for determining when to attempt acquisition of an intruder for active tracking. A link reliability score associated with the intruder is adjusted based upon the signal strength of transmissions, the frequency of the transmissions, and the number of previous attempts to acquire the intruder for active tracking.

Abstract: A method of processing reply signals received in response to an interrogation by a secondary surveillance radar system. The method includes the steps of receiving a reply signal from each of a plurality of targets, and enabling each of a plurality of target mode blocks having a predefined mode to select from the reply signals. The method further includes the step of correlating the selected reply signal to the target mode block that selected same.

Abstract: A tracking data fusion method used in a combined radar/ADS surveillance environment defines track states, track types, and track types transition rules to track aircraft. The best available flight services could be provided if the proposed method is used in an air traffic control system.

Abstract: A method of a Traffic Alert and Collision Avoidance System (TCAS), includes the step of utilizing an MID Subfield for a TCAS Broadcast Interrogation Message that is different than a Mode S address assigned to the own aircraft, the aircraft on which a TCAS is installed. A Traffic Alert and Collision Avoidance System includes a TCAS processing unit that performs a method including the step of utilizing an MID Subfield for a TCAS Broadcast Interrogation Message that is different than a Mode S address assigned to the own aircraft.

Abstract: A method of determining conflicting flight paths between a first and a second airborne vehicle is provided, wherein each vehicle comprises an aircraft-to-aircraft navigational communication system having a navigational device. First, a position and a velocity vector are determined for each of the airborne vehicles. A cylindrical volume is then defined about the first airborne vehicle. A separation distance is then determined between the vehicles at a selected time and using a great circle earth model. An accuracy factor is thereafter determined for the position of each vehicle. The separation distance is then modified by the accuracy factor. A determination is then made as to whether the modified separation distance is within the cylindrical volume about the first airborne vehicle during a time range to thereby determine whether conflicting flight paths exist between the vehicles. An associated system and computer software program product are also provided.

Abstract: A surveillance transceiver system is provided for receiving extended squitters from Mode S transponders, translating the squitters into ADS-B state vectors in UAT format, and transmitting the ADS-B state vectors using a Universal Access Transceiver (UAT) datalink. The surveillance transceiver system bridges the gap created by differently-equipped aircraft by using multiple datalinks to provide seamless ADS-B surveillance. The module for processing the extender squitters includes a 1090 MHz receiver and a computer processor in communication with the UAT processor for parsing the squitter and composing the ADS-B state vector in UAT format for broadcast.

Abstract: Disclosed is a method to determine target azimuth by the use of a radar, especially of the ASR type. The radar sends out a wave of detections by N-pulse bursts. The method comprises at least the following steps in one burst: a step in which the burst is split up into two half bursts, one front burst and one rear burst; a step for the filtering of the half burst to associate an azimuth value &thgr;1 and an amplitude value A1 with the front burst, and an azimuth value &thgr;2 and an amplitude value A2 with the rear burst; a step to obtain the target azimuth Az at a value corresponding to the maximum of a Gaussian curve passing through the points having components (&thgr;1, A1), (&thgr;2, A2). The invention can be applied especially to surveillance radars used, for example, in air traffic management applications.

Abstract: A method and apparatus that permit military aircraft operators to use the civilian Aircraft Addressing and Reporting System (ACARS) technology while ensuring data security.

Abstract: A formation collision avoidance system includes a Traffic Alert and Collision Avoidance System (TCAS) having a passive mode and an active mode. The passive mode enables several members of an aircraft formation to fly without actively interrogating using TCAS while only one or few formation members are actively interrogating. Formation members in passive mode maintain awareness of current air and ground traffic conditions using networked surveillance information provided over a communications link between formation members in active mode and formation members in passive mode. The networked surveillance information includes positional and intent information of current air/ground traffic obtained from ADS-B broadcasts and replies to the actively interrogating members of the formation. The communications link utilizes Station Keeping Equipment (SKE) already existing on certain aircraft.

Abstract: A method for eliminating signals from false targets in a secondary surveillance radar system includes the steps of obtaining plots of radar data for the same target. The range from the radar system to the targets is determined, and the target plot having smallest range of all target plots that indicate reflection of radar signals from the same target is accepted as being a real target. Other target data is rejected as being from a radar reflector. The coordinates of radar reflectors may be stored in a database to form a map of reflectors in the vicinity of the radar.

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.

Abstract: A positioning and proximity warning method for vehicle includes the steps of outputting global positioning system signals to an integrated positioning/ground proximity warning system processor; outputting an inertial navigation solution to an integrated positioning/ground proximity warning processor; measuring air pressure, and computing barometric measurements which is output to the integrated positioning/ground proximity warning processor; measuring time delay between transmission and reception a radio signal from a terrain surface, and computing radio altitude measurement which is output to the integrated positioning/ground proximity warning processor; accessing a terrain database for obtaining current vehicle position and surrounding terrain height data which is output to the integrated positioning/ground proximity warning processor; and receiving the position, velocity and time information or said pseudorange and delta range measurements of said global positioning system, the inertial navigation solution

Abstract: An airport runway incursion detection and warning system for monitoring ground traffic in the vicinity of a runway or taxiway of an airport. The system utilizes a microwave radar transceiver, commonly referred to as a motion detector, connected to a voice annunciator to provide a verbal warning of aircraft or ground vehicle runway incursion. In one embodiment, the microwave transceiver is integrated into a runway lamp and includes a transformer to allow the transceiver to operate from an existing runway lamp power system.

Abstract: An electronic cockpit display of traffic information in a pilot's own aircraft, comprising: a traffic display out to a distance from the own aircraft at a periphery of the display set by an adjustable scale; and a range indicator display representing a selected physical distance from the own aircraft, the range indicator moving in a selectable range ring mode to maintain the selected distance from the own aircraft represented by the indicator as the adjustable scale changes. The range indicator display optionally may be selectively operable in an alternative half-scale range ring mode, in which the range indicator remains at the halfway position on the display as the adjustable scale changes, and in which the physical distance from the own aircraft represented by the indicator varies with the scale adjustment. Range monitoring may be provided using a range ring as the range indicator.

Abstract: A system for correlating secondary surveillance radar (SSR) data and ACARS data which results in a real time correlation of data which are unique to the separate existing systems. More specifically, a method is provided to attach flight identification data from ACARS signals to real time SSR data from Mode S transponders. Aircraft Mode S addresses are decoded and then converted to aircraft registration numbers using an algorithm or lookup table. Registration numbers are then correlated with registration numbers from decoded ACARS signals. The result is a real-time system which may provide an aircraft's registration information, including registration number, owner, make, and model, as well as its current flight identification number, and ACARS messages. As part of an aircraft multilateration system, the system provides an independent air traffic control picture complete with aircraft position and identification by flight number without the use of active radar equipment.

Abstract: A circuit and method for displaying a vertical profile view of situational awareness information.

Abstract: A method, an apparatus and a computer program product are provided for accurately determining the vertical speed of an aircraft in a manner independent of signals provided by an air data computer, an inertial reference system and an inertial navigation system. Initially, a first vertical velocity of the aircraft is determined based upon a pressure altitude value associated with the aircraft. A second vertical velocity of the aircraft is also obtained from a GPS receiver carried by the aircraft. The first and second vertical velocities are then combined to determine the vertical speed of the aircraft. In this regard, the first and second vertical velocities are combined by complimentarily filtering the first and second vertical velocities. More particularly, the first vertical velocity is typically low pass filtered to remove high frequency noise that is attributable to the relatively low resolution of the first vertical velocity value.

Abstract: An apparatus and techniques for predicting conflicts between maneuvering aircraft which does not provide an excessive number of false alarms. The techniques utilize information to limit the time interval during which conflict predictions are made such that the predictions are made when they are most likely to be true.

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.

Abstract: A method, an apparatus and a computer program product are provided for accurately determining the vertical speed of an aircraft in a manner independent of signals provided by an air data computer, an inertial reference system and an inertial navigation system. Initially, a first vertical velocity of the aircraft is determined based upon a pressure altitude value associated with the aircraft. A second vertical velocity of the aircraft is also obtained from a GPS receiver carried by the aircraft. The first and second vertical velocities are then combined to determine the vertical speed of the aircraft. In this regard, the first and second vertical velocities are combined by complimentarily filtering the first and second vertical velocities. More particularly, the first vertical velocity is typically low pass filtered to remove high frequency noise that is attributable to the relatively low resolution of the first vertical velocity value.

Abstract: A number of navigation functions are performed on terrain navigation space. One function is to define a dynamic dangerous zone based on flight altitude by locating and aggregating, a set of nodes of terrain height over a minimum flight altitude. Algorithms such as collision check, mountainous area boundary and region growing technique are developed as basic operations for this terrain model. In addition a visibility graph approach for dynamic route selection may adapted to reduce the real-time computational requirements. This approach reduces the size of the search space by establishing a partial visibility graph of terrain and avoids details of the terrain, which do not influence the choice of flight path, independent of the size of the navigation space. By exploiting the multiple and variable resolution properties of Oct-tree terrain models, a series of CFIT warning functions using terrain data as reference are implemented efficiently with existing-on-board terrain data resources.

Abstract: A method and apparatus for transmitting a directional reply signals in response to Air Traffic Control Radar Beacon System and Mode Select signals interrogation signals. Two directional antennas independently acquire an interrogation signal and are connected by means of a configurable switch to a transponder. The antennas may include multiple directional antenna elements.

Abstract: Weather information is stored in a weather information storage unit. Information of aircraft flight situation, flight plan, air traffic flow management, and condition status is stored in an aircraft information storage unit. On the basis of information stored in the weather information storage unit and the aircraft information storage unit, arrival time of each arriving aircraft and departing aircraft is predicted by an arrival time prediction unit and a departure time prediction unit. The information of the estimated time thus predicted is stored in an estimated time of takeoff and landing storage unit. On the other hand, on the basis of information stored in information storage units, runway use time is assigned to each arriving aircraft and departing aircraft by a takeoff and landing assignment unit in accordance with Control System Standards. Runway reservation information thus obtained is stored in a reservation information storage unit.

Abstract: A combined airborne Air Traffic Control Radar Beacon System/Mode-Select (ATCRBS/Mode-S) surveillance system and Traffic Alert and Collision Avoidance (TCAS) collision avoidance system device having common antennas and a switch coupling the common antennas to the relevant functions.

Abstract: An apparatus and techniques for correlating crossing targets in an air traffic control system is described. The technique utilizes a target/track correlation made on the basis of three conditions: (1) separation distance between a target pair; (2) target polarity and (3) a value of a threshold separation value indicator.

Abstract: A secondary surveillance radar e.g. a Mode-S radar, has a controllable power source in which first and second in-phase r.f. signals are derived from a source (6) by a power splitter (11), and a phase shifter (32) adjusts selectively the relative phase of the signals, so that after amplification by main amplifiers (21, 22) and combination by power comber (23), the resultant power level can be controlled by the phase shift produced by the phase shifter (32).

Abstract: Air traffic surveillance and communication system for air traffic controllers includes a plurality of ground based first digital radio transceivers, each first digital radio transceiver being located in specific geographic sectors, respectively, and having a first frequency channel for supporting party-line digital voice, and a second frequency channel dedicated to supporting a digital data channel for down-linking dependent surveillance data and for both up-link and down-link data communications. The first and second frequency channels are paired such that each time a frequency change is commanded by the ground both the first and second frequency channels will be automatically tuned to a new air-ground frequency pair.

Abstract: An aircraft landing determination apparatus and method for determining landing status of an aircraft by tracking arriving aircrafts and providing a unique runway assignment therefor. The aircraft landing determination apparatus includes a target processor, a track administrator, and a track reporter. The target processor culls multiple target tracks from a target data transmission provided by a target sensor. The track administrator receives the target tracks, selects at least one arrival track therefrom, and allocates a unique runway assignment to each arrival track. The track reporter receives the arrival track and runway assignment, prepares a track report thereabout, and transmits the track report to a position monitoring apparatus.

Abstract: A system for coding and transmitting traffic alert and collision avoidance data between vehicles (A, B and C) traveling within a given airspace (12). The airspace is divided into a grid of volume elements (14a, 14b . . . 14i), each of which is assigned a unique pseudonoise (PN) code. A vehicle (A) traveling through the airspace determines its position using signals from Global Positioning System (GPS) satellites. The vehicle's position places it within one of the volume elements in the airspace. A Traffic Alert and Collision Avoidance System (TCAS) transmitter (38) on the vehicle creates a navigation message that describes the position of the vehicle. A collision avoidance signal is then generated by modulating a carrier signal with the PN code representing the volume element containing the transmitting vehicle and with the navigation message. The collision avoidance signal is transmitted on a common communications channel using time-multiplexing based on a pseudorandom sequence.

Abstract: The present invention provides a combined ground and satellite system for global aircraft surveillance, navigation, landing guidance and collision avoidance which comprises a satellite subsystem consisting of both a satellite constellation and associated ground stations, and a ground subsystem consisting of a network of ground stations, together with an airborne subsystem comprised of a transponder unit located in each of the aircraft using the system. A high speed two-way data link is provided between each of the subsystems using spread spectrum technology to permit overlaying and operation of the system in an existing band of narrow channels with minimum mutual interference. The system of the invention is reliable because of the redundant subsystems, and is not subject to failure. Also, the system provides for computations to be made on the ground, rather than in the aircraft, thereby reducing the size and complexity of the airborne equipment.

Abstract: A device is provided for interrogating airborne SSR transponders at an airport, in which in certain regions which are made non-active, P1 pulses are transmitted followed, with the correct timing, by P2 pulses which have the same or a larger amplitude than the P1 pulses. As a consequence, SSR transponders in these regions are blocked or muted, and this blocking or muting is repeated, whereas in one or a few selected regions, normal interrogating signals are transmitted. Spreading of transmitted pulses to higher levels above ground is countered by keeping the energy of the pulses low and the vertical gain of transmitter antennas small.

Abstract: A communication system is provided for identifying the position of aircraft in a surveillance area. The communication system includes a dual-frequency interrogator which produces two signals at different frequencies. These signals are transmitted over a narrow beam, scanning antenna, the antenna being located within the surveillance area. A transponder is provided on the aircraft with an auxiliary antenna assembly tuned to a frequency equivalent to the difference between the dual frequencies. The transponder produces a signal containing aircraft identification information. A processing unit is co-located on the aircraft with the transponder to receive the two signals transmitted by the interrogator and produce a signal equivalent to the difference between those signals. The difference signal produced by the processing unit is coupled with the transponder and is used to identify the position of aircraft on the ground.

Abstract: The device comprises an analog-digital converter coupled between a pulse receiver and a device to extract the continuous level of the signal given by the receiver. The continuous level extraction device is coupled to an edge detection device and to a scrambling characterizing device to detect the presence of rising or descending edges and of scramblers in the signal given by the receiver.

Abstract: An apparatus for monitoring the position of multiple objects in a space including a target supervisor, a location supervisor, and a hazard monitoring supervisor. The tracking supervisor receives target data from a sensor, characterizes and tracks selected objects, and provides a target output having multiple features respective of the selected objects. The location supervisor characterizes and displays multiple features in the space, and provides a location output having the aforementioned features therein. The hazard monitoring supervisor detects and responds to a predetermined hazard condition, and provides a detectable notice of such hazard condition, responsive to the target output and the location output. A data logger for selectively retains the target output, the location output, or both. The position monitoring apparatus has six modes: full operation, non-airport-surveillance-radar, isolation, set-up, adaptation, and simulation.

Abstract: A communication system for receiving aircraft reply squits (transmissions) normally used in a radar beacon system for surveilling aircraft in a given geographic area. The communication system includes a plurality of omnidirectional receivers, each receiver having a function of omnidirectionally receiving the aircraft squits and developing therefrom two types of information strings, namely a data string, indicative of a message in the aircraft squit, and a corresponding confidence string indicative of the reliability of the developed data string. A data communication link transmits the data and confidence strings between the plurality of omnidirectional receivers and the master data processor.

Abstract: Apparatus for associating target reply signals with target signatures, wherein each reply signal is received from a target transponder within a selectable time period, and further wherein each target signature comprises a first set of parameter values that identify a target position and movement relative to an interrogating aircraft, the apparatus including reply processor means for producing a target report for each reply signal, the target report having a second set of parameter values; and report processing means for: 1) comparing each target report with each target signature to identify which report/signature pairs are potential matches, each comparison between a target report and a target signature being based on comparisons of corresponding parameter values to produce a probability of match for each parameter comparison; and 2) identifying which report/signature matches are best based on comparison of each report/signature potential match with each other potential report/signature potential match includ

Abstract: Apparatus for rejecting multipath reply signals received from a target transponder within a selectable time period, comprising: a top antenna and a bottom antenna to detect reply signals; means for determining an altitude code associated with each reply signal detected by the antennas respectively; means for determining a differential time of arrival (DTA) value for each reply signal detected by the antennas respectively; and processing means for: 1) producing, for each top antenna reply signal, a top antenna target report that includes the altitude code and DTA values; 2) producing for each bottom antenna reply signal, a bottom antenna target report that includes the altitude code and DTA data; and 3) comparing each top antenna report data with corresponding data from each bottom antenna report, and marking out each bottom antenna report that is a multipath reply based on such comparison.

Abstract: An air traffic surveillance and communication system for air traffic controllers, includes a plurality of ground based first radio transceivers located in specific geographic sectors, respectively, and having a first frequency channel for supporting party-line digital voice and a second frequency channel dedicated to supporting a digital data channel for down-linking dependent surveillance data and for both up-link and down-link data communications. The first and second frequency channels are paired such that each time a frequency change is commanded by the ground both the first and second frequency channels will be automatically tuned to a new air-ground frequency paid. The system also includes a plurality of aircraft based second digital radio transceivers, one located in each aircraft. Each second radio transceiver has corresponding first and second frequency channels and a navigational data source on each aircraft.

Abstract: Methods and apparatus for detecting and decoding transponder reply signals of the type having a plurality of associated time discrete pulses including two bracket pulses and a number of related data pulses that may have been transmitted at discrete data time intervals between the bracket pulses such that the signal content detected during the data time intervals corresponds to the reply signal data code, comprising receiver means for receiving the reply signals and producing in-phase (I), quadrature (Q) phase and video (V) signals for each received pulse; means for detecting received pulses and storing the I/Q/V signals in a first memory; means for storing in a second memory pointer values that correspond to the temporal location of pulse I/Q/V signals in the first memory; means for identifying, based on time of arrival (TOA) values, pairs of potential bracket pulses wherein each pair marks the beginning and end of a reply code; and processor means for 1) determining an angle of arrival (AOA) value for each d

Abstract: A proximity warning device for aircraft responds solely to transmissions from transponders. The host aircraft has a host transponder and a signal is generated therein and coupled to the device to indicate transmission of a host reply. Selective suppression is implemented based on presence of an SSR beam which is indicated by the signal. Suppression pulses have a fixed duration but randomly selected intervening durations. Data collection proceeds without regard for suppression or the presence of host replies. The shaping of data collection intervals free of interference from suppression provides for improved efficiency for later data decoding and processing. The signal is used to specially mark collected data generated by a host reply. The ability to discriminate between host and other replies allows completely new performance monitoring functions. In one case, the health of the receiver is deduced from the amplitude of host replies.

Abstract: An airport vehicle identification system includes a ground surveillance radar system which radiates both a conventional radar signal and a beacon interrogation signal. The radar receives i) a backscatter signal from the skin returns of a target and ii) an encoded ID signal indicative of the target identity. The encoded ID signal is transmitted by a vehicle (e.g., an aircraft) mounted transponder in response to receiving the beacon interrogation signal. The transponder can be located within an external vehicle light housing such as an aircraft collision avoidance light. This invention fills the critical void in airport traffic control of providing ground controllers with electronic airport surface surveillance data which includes both vehicle position and identity.