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: Transponder identification record assembly is suitable for associating an identification code with a code recipient and for maintaining an independent record of the identification code associated with the code recipient. The assembly includes a carrier element, a patch, and a data record. The patch is releasably disposed on the carrier element and is further provided with an adhesive coating so that the patch is adherable to the code recipient after the patch is removed from the carrier element. The patch also includes a transponder which stores information such as an identification code. The transponder can be remotely interrogated to obtain the identification code. The data record is disposed on the carrier element separate from the patch. The data record includes at least a copy of the identification code such that, after the patch is removed from the carrier element and adhered to the code recipient, the carrier element bearing the data record can be separately stored.

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: In an air traffic control radar system, a processor is described for correlating primary target data received from a target with a target report and a target track, wherein the processor has a search acquisition time that is adapted to the distance of the target from the radar site. The search acquisition time is shorter for more distant targets. The processor can employ a shorter cycle time (time quantum) to establish a correlation between target data and target reports than would otherwise be possible with conventional fixed search acquisition times. The average total dwell time may be reduced while complying with the mandated maximum processing time for more difficult radar reports.

Abstract: A method for designing an aircraft to ground communications system identifies a plurality of unique functions in the communications system. The components, hardware and software, necessary to implement each of the plurality of unique functions are isolated such that the components for implementing a specific function are partitioned to allow independent testing and certification of the hardware and software components for each unique function.

Abstract: A method for measuring and characterizing the Air Traffic Control Radar Beacon System without interrupting service which comprises a computer-controller system which captures the beacon radar system emissions during one radar rotation and software which extracts and plots the two antenna signal patterns. Data is collected for 50 microseconds during each degree of antenna rotation, triggered by the first pulse of the three pulse signals, and is then stored in separate omni-directional and directional arrays for subsequent plotting. Data is also collected for 50 microseconds during each one-tenth degree of antenna rotation within the directional antenna main lobe.

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: A radar system which time shares the use of a common radar head to perform functions associated with Air Surveillance Radar (ASR) and Precision Approach Radar (PAR) systems, i.e., for respectively displaying information to an air traffic controller useful for tracking an aircraft's approach to an airport and then guiding said aircraft along a preferred glideslope approach to a runway. In accordance with a significant feature of a preferred embodiment, a common radar head is comprised of an azimuth antenna capable of using radar beams to scan, e.g., electronically, a subsidiary scan arc, i.e., less than .+-.90.degree., mounted on a rotational scan apparatus that directs said radar beams within a principal scan arc, a full circle (360.degree.), by continuously rotating, e.g., mechanically, said azimuth antenna at an essentially constant rate.

Abstract: This is a Mode S radio frequency transmission system with coordinated use of a rotating directional antenna and omnidirectional antennas. A software-implemented prefilter both processes messages destined for aircraft equipped with Mode S datalink capable transponders, and prevents any uplink message transmission to a transponder from coinciding with the once-per-scan surveillance interrogation from the rotating antenna as well as any datalink interrogations specified for transmission through the rotating antenna.

Abstract: A method and apparatus for controlling the scan rate of an electronically-scanned (E-scan) antenna (24) of a secondary radar system to provide a variable-dwell time for the E-beam (62) of the E-scan antenna (24) at selected scan angles. The secondary radar system operates in conjunction with a primary radar antenna (20) that scans at a constant angular rate throughout a scan cycle. The E-scan antenna (24) scans through any given azimuth sector at an approximately constant data rate, whereby the beam (62) remains in the azimuth sectors that have high-target densities (52) for extended periods of time and moves rapidly through azimuth sectors that have low-target densities (54).

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 coherent signal generated at a precise frequency determined by an atomic clock is transmitted by a moveable object. A receiver station compares the frequency of the coherent signal received from the moving object with a second coherent signal generated at the same precise frequency by an atomic clock in the receiver to determine the radial component of the velocity of the moveable object relative to the receiver as a function of the doppler shift of the transmitted signal. Low cost, low power, miniature atomic clocks with an accuracy of 10.sup.-11 make possible accurate measurements of velocities of only centimeters per second. Such velocity measurement can be used to enhance radar tracking in air traffic control and collision avoidance systems.

Abstract: An airport surface traffic system is provided which detects targets moving on an airport surface and automatically adds ID codes thereby reduces the controlling duties of an air traffic controller and elevates safety of an aviation control. An airport surface traffic system comprises airport surface monitoring radars which detects targets moving on an airport surface, ASDE target detector which detects targets by an output signal of the airport surface monitoring radars, a second monitoring radar which receives response signals from airplanes and from an airport monitoring radar which controls airport, ASR/SSR target detector which detects targets, ID code addition apparatus which adds an ID code to targets based on a signal from FDP which stores flight schedule data of airplanes and a multi-function display which displays targets.

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 secondary radar uses monopulse reception techniques to improve the estimate of the aircraft position and to improve the reliability of the reply decoding process. Digital signal processing techniques are utilized to replace the analog circuit used in the prior implementations. The secondary radar implements monopulse processing using a half angle phase method wherein the sum and difference signals are encoded in a complete phasor. The detection of the signal and extraction of the azimuth angle data is implemented using a digital receiver concept. The complex phasor is sampled at an intermediate frequency, down converted to baseband and detected. The azimuth angle is computed using arithmetic methods implemented by digital signal processing circuitry.

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: This is a computer-implemented model for the frequency space utilized by the Mode Select Beacon System (the Mode S system) for air traffic surveillance and control. The model simulates the operation of interrogators, transponders, and receivers, and calculates the probability of interference between transponder reply signals using a sliding window.

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: An airspace management system and method includes an alternate quick look mode display option which allows a user to designate a specific geographic region for display in a specified area on a display screen. Within this specified area, which can encompass a portion or all of the display screen, radar plot data is displayed for at least one aircraft for which input radar information is received. Symbols can be assigned to aircraft to differentiate friend and enemy aircraft; colors can be assigned to differentiate friend and enemy aircraft and plots; and radar-measured height information can optionally be displayed. In this quick look mode, near real-time positions for all aircraft within the quick look mode window are displayed, since selection of the quick look mode window bypasses normal time-consuming tracking information processing.

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: In a method of communicating data between a transmission/reception center and a target, a transaction is constituted by one or more interrogation pulses sent out by the center followed by one or more associated reception windows designed to receive the response from the target that has been sent the associated interrogation pulse. The length of a transaction is the delay between its interrogation pulse and its reception window, the transactions are classified and positioned according to their distances from the radar in decreasing order. The reception window of each transaction is transmitted immediately before the window of the immediately lower-ranking transaction so long as its associated pulse does not overlap an interrogation pulse of a transaction.

Abstract: A millimeter wave radar is placed on an aircraft and several radar targets are placed near a runway. The targets are discrete objects, each having a relatively localized radar cross section, a unique signature or a unique range bin, and a position which is accurately known. Targets should be spread over the length of the runway. Radar corner reflectors and active or passive repeaters are preferred. The locations of the radar targets with respect to the runway can be transmitted to the aircraft, or they can be stored on board. On board memory requirements can be reduced by requiring all airports to select one of only a few standard target placement patterns, or even only one. Targets are inexpensive, as are radars whose only precision requirement is in range, and not in azimuth or elevation angles. Range to at least three targets in the radar's field of view is all that is required for an on-board computer to determine the aircraft's location.

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: Disclosed are a device for the detection of S mode responses received by a secondary radar receiver and its use for the filtering of the pulses contained in this response. The device furthermore comprises means to detect a signal S, means for the real-time computation of the mean values of magnitudes characterizing the pulses that belong to the response, and means for the filtration, by comparison, of the values of the magnitudes measured on each pulse detected with the mean value of the corresponding magnitude.

Abstract: Disclosed are a method and device for the real-time processing of the responses constituted by pulse signals emitted by secondary radar transponders. The device has an analyzer of sampled magnitudes characterizing the pulses, said magnitudes being prepared by a device located upline with respect to the disclosed device. This device creates a sample message at the sampling rate. Said sample message characterizes the variations of the different magnitudes from one sample to another. A device for the processing of the pulses receives the sample messages and prepares pulse messages. Finally, a device filters the pulses belonging to a same response from the information elements pertaining to the pulse messages and from response detection signals.

Abstract: An airport vehicle identification system for improving airport traffic management and collision avoidance, includes a ground surveillance radar and a plurality of low power frequency translators located in spaced relationship about the surface of the airport. The radar system transmits a conventional radar signal for target detection and a beacon interrogation signal for target detection. Each translator is designed to bandshift the interrogation signal to a frequency value compatible with the vehicle transponder, and transmit the bandshifted interrogation signal to the vehicle transponder. Each frequency translator is bi-directional and receives a transponder reply signal indicative of vehicle identity and bandshifts the reply signal to a frequency value compatible with the ground surveillance radar and transmits the bandshifted reply signal to the ground radar.

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: A method and means for evaluating transponder reply signals in a secondary radar system to differentiate valid replies from false replies. Transponder reply signals received by the interrogating radar are decoded to establish conformity with an established format. All decoded replies to a succession of N interrogation signals are stored in their order of reception in an array of N shift registers. A reply filter is associated with each of the N shift registers. The reply filters operate in parallel to scan the stages of each associated shift register. A unary adder provides the number M of replies detected by the reply filters at each scan step. Reply decision means selects a threshold value that is dependent upon operating conditions of the radar and generates a valid reply signal whenever the value M equals or exceeds the selected threshold value.

Abstract: Conventional secondary radar systems use mechanically rotating antennas to radiate a concentrated beam that rotates in a horizontal plane. Data exchange between ground stations and airborne transponders can only take place if the aircraft is struck by the antenna lobe. The distance from the aircraft to the ground station is determined from the signal transit time. Directional information is derived from the antenna position. The secondary radar system according to the invention uses an omnidirectional antenna, so that data can be exchanged between ground station and aircraft at any time. To determine the position of the aircraft, interrogation signals are transmitted by a single active ground station such that the reply signal from a transponder falls within the common system time frame of the ground station. The times of arrival of the reply signals at different ground stations are then directly proportional to the distances from the aircraft to these ground stations.

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.

Abstract: A method of processing a plurality of tracks representative of one or more target aircraft in a vicinity of a surveillance aircraft, where each track is generated in response to target reply signals provided by the target aircraft in response to interrogation signals transmitted by the surveillance aircraft, includes eliminating a portion of the plurality of tracks which are duplicate tracks of the same target aircraft. The remaining tracks are maintained and updated in response to the target reply signals provided by the target aircraft. A threat level for each of the remaining tracks is determined and two or more of the remaining tracks which are possibly representative of a same target aircraft are merged resulting in a composite track. The composite track is output to a display device utilizing information from a particular remaining track of the composite track having the greatest threat level to the surveillance aircraft while continuing to maintain and update all the remaining tracks.

Abstract: A method of processing a plurality of replies of target aircraft provided in response to interrogation signals from the surveillance aircraft during surveillance periods to determine whether an altitude track may be initialized for use in a traffic alert and collision avoidance system includes the step of selecting three replies, one from each of three consecutive surveillance periods. The replies have binary or coded altitude data of high or low confidence. The binary or coded altitude data of non-adjacent and adjacent replies of the selected replies are compared and an altitude difference value for each of the comparisons is generated. Further efforts to initialize a track are discarded if any of the altitude difference values are greater than first predetermined separated altitudes if and only if such compared non-adjacent and adjacent replies have binary or coded altitude data of high confidence.

Abstract: This invention concerns a secondary radar antenna operating in S mode.The antenna comprises a row of columns (1) of radiating elements powered by a hyperfrequency distribution circuit (2) containing a summing channel (.SIGMA.), a difference channel (.DELTA.) and a secondary lobe suppression channel (.OMEGA.), each producing a radiation diagram. The antenna end columns (L, R) each produce at least one auxiliary radiation diagram offset with respect to the diagram produced by the summing channel and contributing with the other antenna columns (1) to the creation of the other three diagrams.Application: secondary radars in S modes in communication with a large number of aircraft per antenna revolution.

Abstract: In a Traffic Alert and Collision Avoidance System on an aircraft having a plurality of antennas, an optimal bearing value is obtained for each target aircraft by generating a target data block for each response to an interrogation, each target data block including a measured bearing value and an associated priority code. A priority code is assigned based on the antenna receiving the information, and the number of valid bearing measurements used to determine a measured bearing value for the reply. If more than one target data block is obtained in a surveillance period, one target data block is retained based on predetermined criteria. The measured bearing value of all the target data blocks having the same, highest priority code are selected or combined, the result being saved in the target data block. The priority codes are then used to select the proper reply bearing measurement, the bearing track update filtering parameters, and to aid in the reply qualification for bearing track initialization.

Abstract: The range from which transponder replies can be received at a virtual secondary surveillance radar of the type described in U.S. Pat. No. 4,115,771 is extended by replacing the omnidirectional antenna previously utilized to receive replies from transponders within the range of the SSR with a stationary array of a plurality of directive antennas arranged in a circle and having radiation patterns pointing in different directions from the center of and covering a respective sector of the circle, and sequentially switching on the antenna of the array covering the sector in which the rotating beam of the associated SSR is then pointing.

Abstract: A secondary surveillance radar system combines a mechanical scanning type of mode-S sensor using a mechanical rotation type of antenna and an electronic scanning type of mode-S sensor using an electronic scanning type of antenna. The mechanical scanning type of mode-S sensor performs at least mode-A/C general inquiry/response with aircraft targets and create a file of surveillance data obtained by the general inquiry/response. This allows circumvention of problems, which would be encountered in performing the same processing by using the electronic scanning system, such as the deterioration of accuracy of monopulse angular measurement, the increasing probability that unwanted responses will be received, etc., which are due to the elevation dependence of horizontal beamwidths.

Abstract: The invention provides a Secondary Surveillance Radar (SSR) to be used on airports, in which the airport is divided in a considerable number (preferably 100 to 250) divisional regions, each of said regions having at least one and preferably at least two transmitters (1,2 if FIG. 1; 1,3; 2,4; 3,5; 4,6 in FIG. 4) and at least two receivers (1,2,3 in FIG. 1; 1,2,3; 2,3,4; 3,4,5; 4,5,6 in FIG. 4) to determine the location of interrogated transponder by means of multilateration, in which a transmitter may have the same location as a receiver and the transmitters and receivers are connected to a central processor.

Abstract: A virtual secondary surveillance radar (VSSR) of the type described in U.S. Pat. No. 4,115,771 can produce inaccurate or indeterminate range information for a transponder positioned on or near a line between the actual SSR and the VSSR, owing to unfavorable geometrical relationships. This can be avoided by receiving the SSR interrogation and reply signals at two or more separated locations and processing the signals to provide positional information at a display site. No radar transmissions other than those of the existing ATCRBS are required.

Abstract: Disclosed herein is a method and apparatus for a ground radar and information display system for commercial and general aviation. The method includes processing raw data from the presently existing ATCRBS system, duplicating the raw data and sending it to an auxiliary computer, filtering out non-positional messages of the raw data, encoding the raw data into a data block and transmitting the data block to a display facility, where it is decoded and displayed. The apparatus of the invention includes and auxiliary ground computer and a smaller on-board computer for processing the data block.

Abstract: In a Traffic Alert and Collision Avoidance System (TCAS), response to interrogations can result in normal, multipath (image), and mixed multipath (potential image) tracks. The method for reducing the number of false tracks includes the steps of selecting a track to be updated from an existing track list. The selected track has the shortest measured range within the highest priority category track. A reply which has not yet been utilized is selected which has parameters which are within predetermined windows of the selected track parameters. (The predetermined windows are equal to or smaller than the windows for lower priority targets.) The selected track is updated using .alpha..beta..gamma. range squared filter, and the selected reply is marked as used. After all tracks are updated, the unused replies are tested to generate new tracks. Then all the tracks are examined to insure that predetermined track category criteria are met, otherwise the track is recategorized.

Abstract: An airborne surveillance method and system allows an observer aircraft to determine the position and change of position of a multiplicity of target aircraft and thus allows analysis of collision threats from these aircraft. The system uses a phase comparison direction finding antenna to determine direction of nearby ground based SSRs and all target aircraft of interest. The system further makes use of all other available data including Mode C transponder generated altitude information of the target aircraft, the altitude of the observer aircraft, the received signal strength of both the SSR beam and the received transponder signal, the time difference of arrival between the SSR interrogation signal and the response from the target aircraft, and a variety of other factors to determine the position of the target aircraft.

Abstract: A system for transmitting aircraft beacon information received by a secondary surveillance radar through telephone lines to a remote display includes a digitizer connected to the radar for preparing a serial file of data records containing position and identification information of the beacons detected by each sweep of the radar. This information is transmitted through the telephone lines to a remote computer where it is displayed.

Abstract: A secondary surveillance radar system in which monopulse processing is used to obtain angle estimation of azimuth bearing, the improvement residing in a precision method, involving a monopulse qualifier signal, for identifying the maximum unambiguous off-boresight azimuth (OBA), while ensuring reduced sensitivity to Omni channel variations; the monopulse qualifier signal is developed from coherently combining the IF limited signals derived from the Sum+JDelta and Delta+jSum signals, such that two amplitude varying signals are created, such signals bearing a direct relationship to the Sum and Difference antenna pattern ratios and being independent of antenna signal power.

Abstract: The device improves the decoding of the replies in S mode deformed by multiple-path phenomena or by imbrication with replies in standard A or C mode. To do this, the device carries out the following in the reception video signal Log .SIGMA. of the secondary radar: determines a pulse level reference value of the data block of the reply by a study of the histogram of the presumed pulse levels of data and compares the level of the reception signal Log .SIGMA. taken at the middle of each time interval that may be occupied by a data pulse with the level reference value, a data pulse being detected or not detected according to the result of the comparison. Should there be a negative result in a baud period, it may recommence similar operations on the angle measurement video signal .SIGMA./.DELTA. if the secondary radar is a monopulse radar.

Abstract: Disclosed herein is a method and apparatus for a ground radar and information display system for commercial and general aviation. The method includes processing raw data from the presently existing ATCRBS system, duplicating the raw data and sending it to an auxiliary computer, filtering out non-positional messages of the raw data, encoding the raw data into a data block transmitting the data block to a display facility, where it is decoded and displayed. The apparatus of the invention includes and auxiliary ground computer and a smaller on-board computer for processing the data block.

Abstract: A guidance system for landing an aircraft is described which uses a source of signals identifiable with the aircraft and a ground station which is linked to the aircraft. Specifically, the ground station includes a receiver which is connected to one or more pairs of antennas having a fixed, overlapping, directional sensitive pattern symmetically located relative to the center of the landing path, a receiver and a processor for measuring the relative sensitivity of the signals received at the antennas and for using the relative signal intensity to determine the location of the aircraft relative to the center of the landing path.