Abstract: A passive airborne mounted collision warning system suitable for light aircraft that enables an observer aircraft to determine the position of a nearby transponder-equipped target aircraft. The transponder-equipped target aircraft transmits replies responsive to interrogation signals from rotating secondary surveillance radars (SSR). In an embodiment of the invention, position of the target aircraft is determined based on the known position of the observer aircraft obtained e.g. via satellite navigation means such as GPS, the position of the SSR, and the bearing of the target aircraft measured by a direction finding antenna. The direction-finding antenna elements and the GPS receiver components are included in a device that is externally mounted on the observer aircraft. The data from the device is connected to a portable computer for processing and presentation to the pilot to alert him of the position of the target aircraft for avoiding collisions.

Abstract: A transceiver or transponder particularly for synthetic aperture radar, or SAR, systems, operating in a frequency band having a central frequency, the transponder comprising a receiver (1) and a transmitter (2) both thermally stable and made by microstrip technology, the receiver (1) and the transmitter (2) being adapted to receive and to transmit, respectively, an electromagnetic wave provided with at least one linear polarisation, the receiver (1) being connected to the transmitter (2) by amplifier means comprising an amplifier unit (5) for each linear polarisation of the wave received by the receiver (1), each amplifier unit (5) including at least two amplifier stages (7, 9, 11) cascade arranged along a single microstrip and interconnected to one another and to an input and to an output of the corresponding amplifier unit (5) by means of coupling or matching stages (6, 8, 10, 12), the output signal of each amplifier unit (5) having substantially the same frequency as the input signal thereto, the amplifier

Abstract: A target designation system for indicating a target to be destroyed by remotely guided ordnance comprising a receiver arranged to produce a receiver output signal in response to an incident electromagnetic signal from an attack aircraft. An auto-switch is connected to the receiver and arranged to produce a power signal in response to the receiver output signal. A transmitter is connected to the auto-switch to be activated by the power signal. When activated, the transmitter transmits a homing signal that indicates its location or the location of the target.

Abstract: SAW devices such as interdigital transducers (IDTs) have been widely used in RADAR applications and as filters. An IDT produces a SAW when excited by a single electrical pulse and can be fabricated to embody a code, which code provides for a passive autocorrelation of a SAW input to the IDT and thereby lends itself to further application as a signal generator in a communication device. However, internal dimensions of IDTs are inversely proportional to operating frequency, such that high frequency IDTs present significant manufacturing difficulties. Fabrication of IDTs for high frequency applications is simplified by exploiting a harmonic frequency SAW generated by IDTs. An IDT may therefore be designed according to fundamental frequency internal dimension criteria but can operate at a multiple of the fundamental frequency, thereby providing much higher frequency operation than conventional SAW systems.

Abstract: A transponder lock provides allows an aircraft transponder to continue transmitting an alerting code for the duration of an emergency. The transponder lock thereby enables the aircraft transponder to continue to provide crucial information to ground tracking stations. Installation of the transponder lock results in very little aircraft downtime because the transponder lock connects in-line with existing aircraft wiring.

Abstract: An RFID system using encoded digital information utilizing pulsed linear frequency modulation (LFM). The LFM waveform is sent from an24 aircraft or satellite and is received by a transponder. The LFM waveform is demodulated using both, an AM and an FM receiver. The demodulated data is compared to preprogrammed criteria tables, and after validation is decoded and utilized. Algorithms in the transponder are used to determine the frequency deviation and for calculating the direction of the slope of the LFM input signal. The valid RF signal is stored in a delay element, encoded with the transponder data using phase modulation (PM), and frequency modulation (FM). The tag transmission is synchronized to the input LFM waveform. The transmit/receive chopping signal prevents unwanted oscillations and is capable of randomization.

Abstract: An RFID system using encoded digital information utilizing pulsed linear frequency modulation (LFM). The LFM waveform is sent from an aircraft or satellite and is received by a transponder. The LFM waveform is demodulated using both, an AM and an FM receiver. The demodulated data is compared to preprogrammed criteria tables, and after validation is decoded and utilized. Algorithms in the transponder are used to determine the frequency deviation and for calculating the direction of the slope of the LFM input signal. The valid RF signal is stored in a delay element, encoded with the transponder data using phase modulation (PM), and frequency modulation (FM). The tag transmission is synchronized to the input LFM waveform. The transmit/receive chopping signal prevents unwanted oscillations and is capable of randomization.

Abstract: A method of locating an underground utility line. A first step involves securing transponders along a length of an underground utility line at regular spaced intervals. A second step involves interrogating the transponders to receive transponder signals. A third step involves ascertaining the position of the transponder signals and extrapolating positioning of the underground utility line from the transponder signals.

Abstract: A millimeter wave beacon includes a millimeter wave transmitter that produces at least one signal and plurality of antennas, coupled to the millimeter wave transmitter, that each emit millimeter wave radiation in response to the at least one signal. In one embodiment, the antennas are constructed and oriented to produce an overlapping signal field in which millimeter wave radiation emitted from multiple of the antennas can be detected. The millimeter wave radiation can be pulsed to encode various information of interest. Determination of the direction of approach to the beacon is facilitated by multiple antennas transmitting signals having different pulse encodings and/or different frequencies.

Abstract: A target designation system for indicating a target to be destroyed by remotely guided ordnance comprising a receiver arranged to produce a receiver output signal in response to an incident electromagnetic signal from an attack aircraft. An auto-switch is connected to the receiver and arranged to produce a power signal in response to the receiver output signal. A transmitter is connected to the auto-switch to be activated by the power signal. When activated, the transmitter transmits a homing signal that indicates its location or the location of the target.

Abstract: A target designation system for indicating a target to be destroyed by remotely guided ordnance comprising a receiver arranged to produce a receiver output signal in response to an incident electromagnetic signal from an attack aircraft. An auto-switch is connected to the receiver and arranged to produce a power signal in response to the receiver output signal. A transmitter is connected to the auto-switch to be activated by the power signal. When activated, the transmitter transmits a homing signal that indicates its location or the location of the target.

Abstract: A method and apparatus are provided that determine a frequency dependent calibration vector for a set of transmit or receive chains of a radio communications system using only differential phase and amplitude between the transmit chains and the receive chains, respectively. In one embodiment, the invention includes an antenna array adapted to transmit and receive radio communications signals with a plurality of other terminals, a transmit chain to transmit a calibration signal through the antenna array to a transponder on at least two different frequency bands, and a receive chain to receive through the antenna array a transponder signal from the transponder, the transponder signal being received on at least two different frequency bands and being based on the calibration signal.

Abstract: A multi-frequency RFID remote communication system is provided that includes a plurality of RFID tags configured to receive a first signal and to return a second signal, the second signal having a first frequency component and a second frequency component, the second frequency component including data unique to each remote RFID tag. The system further includes a reader configured to transmit an interrogation signal and to receive remote signals from the tags. A first signal processor, preferably a mixer, removes an intermediate frequency component from the received signal, and a second processor, preferably a second mixer, analyzes the IF frequency component to output data that is unique to each remote tag.

Abstract: Methods and Apparatus for early detection and identification of a threat, and alerting against detected threats, such as individuals wearing or carrying explosive materials and/or weapons, e.g., suicide bombers and other terrorists, at a great enough distance to limit loss of life and destruction of property are disclosed. The methods comprise transmitting a signal in the direction of a potential threat, measuring the detected reflected signal, and comparing the signal level with a threshold indicative of a threat. A monitor is employed to display the threat and attributes of the detected signals. The invention further illuminates the suspicious individual(s) with a Laser illuminator/designator and provides information about the distance to the suspicious individual(s).

Abstract: A device for data transmission in a motor vehicle and/or from a motor vehicle in its vicinity includes a first transceiver unit in or on the motor vehicle and a second transceiver unit. which is provided in at least one transponder unit whose spatial position relative to the vehicle may be variable or any desired position. In the first transceiver unit is a radar unit equipped for distance measurement, expanded by adding a two-channel data transmission system. The second transceiver unit is also a two-channel data transmission unit, and the microwave frequencies for two-channel communication of the data transmission system are selected so that their difference yields an intermediate frequency which is processable using conventional components in a heterodyne receiver in the reception part of each of the first and second transceiver units.

Abstract: A target designation system for indicating a target to be destroyed by remotely guided ordnance comprises a receiver arranged to produce a receiver output signal in response to an incident electromagnetic signal from an attack aircraft. A switch is connected to the receiver and arranged to produce a power ON/OFF signal in response to the receiver output signal. A transmitter is connected to the auto-switch to be selectively activated and deactivated by the power ON/OFF signal. When activated, the transmitter transmits a homing signal that indicates its location or the location of the target being illuminated by the transmitter signal.

Abstract: The invention relates to a system suitable for a remote interrogation of passive transponders using chirp signals for interrogation. The transponder preferably has an encoding unit (11), a calibrating unit (12) and a measuring unit (13) each with a plurality of parallel channels (11.1 to 11.5, 12.1 and 13.1 to 13.2). The encoding unit and the calibrating unit are preferably jointly incorporated with a common delay line (14) on the same SAW chip. The interrogation signals received in the transponder via an antenna (10) are delayed characteristically and code-specifically, in particular in the encoding and calibrating unit. Decoding in the interrogation station is preformed by discrete Fourier transformation of the response signal and subsequent evaluation of the spectrum. To correct general disturbing influences on the delay of the response signal, said signal is calibrated using a single calibrating component in the response signal.

Abstract: A police activity transponder utilizes data available through a vehicle on-board diagnostic system or a intelligent vehicle data bus to adjust the sensitivity of the police activity transponder to law enforcement signals based on speed data. A police activity transponder is configured to read speed data available through an on-board diagnostic system or an intelligent vehicle data bus and using an internal clock, calculate a 0 to 60 mile per hour or a quarter mile time for display and function as a speedometer. A police activity transponder is configured to read engine revolutions per minute (rpm) data and function as a tachometer. A police activity transponder is configured to allow a user to input shift points, read engine rpm data, and provide a user indication.

Abstract: A backscatter transponder interrogator, comprising a transmitter, emitting an interrogation signal for interacting with a backscatter transponder within an interrogation field, a plurality of antennas, each having a different and complementary property, such that a backscatter response from a backscatter transponder is likely to be preferentially received by at least one of said at least two antennas, a receiver, selecting an output from a selected antenna, and demodulating the backscatter response to produce an information signal, and a digitally controlled oscillator, producing an output controlling said transmitter and employed by said receiver to demodulate the backscatter response. The interrogator may have a plurality of transmit antennas. The antennas may have respectively different polarization properties, e.g., horizontal and vertical polarization. The interrogator may implement null steered polarization cancellation to distinguish between backscatter transponders within the interrogation field.

Abstract: A transmitter and method for transmitting transponder or TCAS signals uses linear amplification to save on circuit component weight, cost and size while enabling precise amplification and control of the transmitted signal.

Abstract: A method and apparatus are provided that determine a frequency dependent calibration vector for a set of transmit or receive chains of a radio communications system using only differential phase and amplitude between the transmit chains and the receive chains, respectively. In one embodiment, the invention includes an antenna array adapted to transmit and receive radio communications signals with a plurality of other terminals, a transmit chain to transmit a calibration signal through the antenna array to a transponder on at least two different frequency bands, and a receive chain to receive through the antenna array a transponder signal from the transponder, the transponder signal being received on at least two different frequency bands and being based on the calibration signal.

Abstract: A cooperative tracking system designed to track multiple cooperative targets within a given field in real time with high precision and high update rate comprises a microwave transmitter and two receivers with each target being provided with one or more coded microwave transponders which enable calculation of both position, speed and in a preferred embodiment direction of movement of each target.

Abstract: A method and apparatus are provided for sensing two-dimensional identification marks provided on a substrate or embedded within a substrate below a surface of the substrate. Micropower impulse radar is used to transmit a high risetime, short duration pulse to a focussed radar target area of the substrate having the two dimensional identification marks. The method further includes the steps of listening for radar echoes returned from the identification marks during a short listening period window occurring a predetermined time after transmission of the radar pulse. If radar echoes are detected, an image processing step is carried out. If no radar echoes are detected, the method further includes sequentially transmitting further high risetime, short duration pulses, and listening for radar echoes from each of said further pulses after different elapsed times for each of the further pulses until radar echoes are detected.

Abstract: A method and apparatus is provided for remotely and constantly calibrating a transponder by using the ring around phenomenon. A number of different time varying physical quantities, such as for example temperature, signal level, noise, transmission line flex, frequency, and general operational effects, affect the inherent delay in transponders on a time varying basis. The invention relies on a the ring around phenomenon to produce pulse doublets, wherein the distance between the pulses in the pulse doublets correspond to the instantaneous delay in the transponder. The system is configured so that instantaneous variation in the transmission delay is detected and recognized on a pulse by pulse basis and transmitted to the interrogation device, which then functions to calculate the actual delay. Normal operation of the transponder is not affected by the continuous calibration method, and therefore a special calibration mode is not required.

Abstract: When a question signal of a transmitting frequency band &Dgr;F1 output from a radar device is received in search and rescue radar transponder (SART) of a wreck ship, a response signal is sent from the SART to the radar device. In the radar device, the response signal and an echo of the question signal are received as a reception signal, intensity of components of the reception signal placed in almost the same frequency band as the transmitting frequency band &Dgr;F1 of the question signal is suppressed to produce a filtered response signal, and components of he filtered response signal placed in a receiving frequency band &Dgr;F2, which does not overlap with the transmitting frequency band &Dgr;F1 of the question signal, are extracted from the filtered response signal as an image signal.

Abstract: A dual channel microwave sensor employs single sideband Doppler techniques in innumerable vibration, motion, and displacement applications. When combined with an active reflector, the sensor provides accurate range and material thickness measurements even in cluttered environments. The active reflector can also be used to transmit multi-channel data to the sensor. The sensor is a homodyne pulse Doppler radar with phasing-type Doppler sideband demodulation having a 4-decade baseband frequency range. Ranging is accomplished by comparing the phase of the Doppler sidebands when phase modulated by an active reflector. The active reflector employs a switch or modulator connected to an antenna or other reflector. In one mode, the active reflector is quadrature modulated to provide SSB reflections.

Abstract: SAW devices such as interdigital transducers (IDTs) have been widely used in RADAR applications and as filters. An IDT produces a SAW when excited by a single electrical pulse and can be fabricated to embody a code, which code provides for a passive autocorrelation of a SAW input to the IDT and thereby lends itself to further application as a signal generator in a communication device. However, conventional SAW expanders and compressors typically have insertion losses greater than 20 dB, which can have a profound effect on an RF link budget in a communication system. Insertion losses are drastically reduced by using a single phase unidirectional transducer (SPUDT-type) instead of a conventional IDT as a SAW expander/compressor. A SPUDT-type reflects SAW components which are lost in conventional IDT designs so that a stronger SAW is directed toward a transmission element. In a receiver, a SPUDT-type directs a stronger SAW toward a compressor IDT.

Abstract: A pre-crash sensing system is provided for sensing an impact of a target vehicle (46) with a host vehicle (12). The target vehicle (46) has side transponders that generate side identification signals. The host vehicle (12) has a remote object sensor (20) that generates an object distance signal in response to the target vehicle. A countermeasure system (42) resides in the host vehicle (12). A controller (14) in the host vehicle is coupled to the remote object sensor (20) and the countermeasure system (42). The controller (14) activates the countermeasure in response to the object distance signal and side identification signal.

Abstract: Methods and apparatus for determining location information corresponding to a volume in space (VIS) that is occupied by a selected target from a remote observation platform through the process of collecting an identification signal from a source at or near the selected target and associating VIS location information data with that signal to identify location information corresponding to the VIS occupied by the target.

Abstract: The invention relates to a system suitable for a remote interrogation of passive transponders using chirp signals for interrogation. The transponder preferably has an encoding unit (11), a calibrating unit (12) and a measuring unit (13) each with a plurality of parallel channels (11.1 to 11.5, 12.1 and 13.1 to 13.2). The encoding unit and the calibrating unit are preferably jointly incorporated with a common delay line (14) on the same SAW chip. The interrogation signals received in the transponder via an antenna (10) are delayed characteristically and code-specifically, in particular in the encoding and calibrating unit. Decoding in the interrogation station is preformed by discrete Fourier transformation of the response signal and subsequent evaluation of the spectrum. To correct general disturbing influences on the delay of the response signal, said signal is calibrated using a single calibrating component in the response signal.

Abstract: A securing system, in particular for motor vehicles, comprises at least one multi-functional sensor, which is simultaneously provided both as a radar unit and as a transmitter/receiver unit for communicating with an external device such as a user identifying transponder. The device may have multiple transmitters and/or receivers spatially situated to determine whether the external device is inside or outside the vehicle and may emit a HF-modulated signal that is frequency shifted and re-emitted by the external device and received by the multi-function sensor, wherein a security function may be performed based on both identifying information in the re-emitted HF-modulated signal and the distance to the transponder determined from the time duration between emission of the HF-modulated signal and reception of the re-emitted HF-modulated signal.

Abstract: A reply is received from aircrafts for calibration in response to an interrogation of SSR stations to detect transmission timing of the interrogation of the SSR stations and directly-facing timing of antennas of the SSR stations and thus detect a position of an arbitrary aircraft based on the transmission timing and directly-facing timing and the reply from the aircraft.

Abstract: A transponder for automatic identification and corresponding systems. The transponder may include patch antennas for reflecting transponder data as information sidebands of a microwave signal received from a reading unit, for example. The antennas may by parallel to, but oppositely directed from one another. Additionally the antennas may act against at least one intermediate earth plane, and are linearly polarized so that their polarization direction is rotated through 90° in relation thereto. In this arrangement, the transponder may be read from a short distance and from both sides of the antennas, and communication with the transponder may not be disturbed by the presence of a rearwardly-located reflection plane.

Abstract: An improved traffic alert and collision avoidance method and device wherein TCAS data is augmented by higher resolution radar data. By using radar to search out targets, altitude information can be developed for those aircraft not equipped with altitude reporting transponders. The improved accuracy also allows angle/angle perspective display of air traffic and thus provides enhanced situational awareness.

Abstract: Novel means of achieving increased security while still obtaining a low cost, manufacturable device are disclosed and claimed. The first mode of operation is the learn mode which provides means for initial checkout with no security. In the learn mode of operation, the interrogator and transponder may be switched to a predetermined error detection algorithm, i.e. CCITT(Start Mask, CCITT Mask), and certain information is programmed into the transponder memory. During programming, all the bits received from the interrogator are shifted through the preintialized CRC generator. In addition, once the transponder response is sent back to the interrogator, the response is also shifted through a preinitialized CRC generator within the interrogator(which could be a software implementation). Because neither the Cypher Key nor the Function Key are directly readable once programmed, an encryption must be performed to verify the proper Cypher Key and Function Key were programmed into the transponder's memory.

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: An anticipatory object detection system includes a transducer device for transmitting a modulated carrier signal and receiving the reflected modulated carrier signal from an object; a detection device for detecting a plurality of Doppler shifted harmonic components from the reflected modulated carrier signal; a range determining device responsive to the amplitude of at least two of the harmonic components for determining the instantaneous range of the object; a velocity measurement device, responsive to the frequency of at least one of the harmonic components, for determining the relative, instantaneous velocity of the object.

Abstract: A system and apparatus for enhancing the satellite based navigation systems which includes providing an aircraft with an interrogating radar for interrogating beacons disposed at a predetermined location in front of a runway wherein the beacons are radar-activated passively powered runway beacons.

Abstract: An active reflector including an antenna, a frequency converter, and a delay circuit is placed at a location within an area to be detected by a synthetic aperture radar. The active reflector receives an incoming radio wave emitted by the synthetic aperture radar and changes its frequency or delay time. The resultant radio wave is transmitted as a reflected radio wave toward the synthetic aperture radar. As a result, the position of the active reflector image displayed on the screen of the synthetic aperture radar is shifted. The ambiguity is quantitatively detected from the pixel value at the original display position at which the active reflector image was displayed before it was shifted, thereby evaluating the image quality of the synthetic aperture radar.

Abstract: Doppler control circuit for a CW or pulse Doppler radar system for monitoring not only the phase shift between echo signals from several targets but also the amplitude difference between the several targets and to further provide a phase lock loop which tunes the radar to a particular target among one or more targets from which echo signals return. The control circuit can be used in state of the art CW or pulse Doppler type radar systems. In a further system, a continuously generated radar signal is repeatedly transmitted at three different frequencies in time division fashion to define a succession of transmit and receive frames. The receive frames are divided into a plurality of time interval windows with selected windows being used to detect received signals at the different frequencies. The remaining windows can be used for subsystems of the radar system.

Abstract: A stabilizing method of a synthetic aperture radar and a position determining method by the radar. At least three repeaters are arranged in mutually different positions on the ground or the sea and a radio frequency signal having a predetermined frequency is transmitted from the radar mounted on a radar platform such as an aircraft to the repeaters. Each repeater frequency-modulates and amplifies the received signal to return the signal to the radar. The radar receives the signal returned from each repeater. The radar calculates a distance between the radar platform and each repeater on the basis of a time required for the transmitting and the receiving and phase information of the received signal. When the position of each repeater is known, by using the positions of the repeaters and the calculated distances, the position of the radar platform can be calculated. On the basis of the obtained position of the radar platform, a reference signal for phase compensation is generated.

Abstract: An active, phase-coded, time-grating transponder and a synthetic-aperture radar (SAR) and signal processor means, in combination, allow the recognition and location of the transponder (tag) in the SAR image and allow communication of information messages from the transponder to the SAR. The SAR is an illuminating radar having special processing modifications in an image-formation processor to receive an echo from a remote transponder, after the transponder receives and retransmits the SAR illuminations, and to enhance the transponder's echo relative to surrounding ground clutter by recognizing special transponder modulations from phase-shifted from the transponder retransmissions. The remote radio-frequency tag also transmits information to the SAR through a single antenna that also serves to receive the SAR illuminations.

Abstract: An identification/security tag system, including miniaturized tags which can be readily concealed, utilizes a concept of "electronic" Doppler shifting to generate a frequency shifted signal in response to an interrogation signal. The frequency shifted signal is used to identify individual tags. The implementation of electronic Doppler shifting permits the utilization of conventional police/sport radar guns as a combined transmitter and receiver unit, thereby greatly reducing the expense of the system. The high frequency operation of the system permits size of the tag to be significantly reduced with respect to the size of tags used in conventional tag systems. Rectenna circuitry is further employed to eliminate the need for an active power supply in the tag in some applications.

Abstract: An improved system and method for detecting and positively identifying with nhanced IFF techniques an object or target from an interrogator platform where the area outwardly of and about the platform is suitably surveyed for detecting an object and where the platform is on the earth's surface, in the air or space so long as the platform and detected object to be identified are both within the envelope defined by the Global Position System (GPS) or the like. The system for carrying out the method can be generally made up of a GPS receiver, a programmed central processor unit and combined transceiver/antenna means. The GPS receiver of any platform after detecting an object advantageously functions to obtain the platform geoposition. Then by suitable means or by the cooperation of the programmed processor and antenna means obtain the bearing of the detected object. The detected object is then interrogated with an encrypted IFF signal as to the estimated position of the detected object.

Abstract: A collision avoidance system for sea navigation comprises, for each equipped ship, a transmitter that repeatedly transmits the geographic coordinates, course and speed of its own ship and a receiver that sends a display device similar data received from other ships. These received data are displayed, mostly in the form of symbols, on the panoramic screen of the display device.

Abstract: An interrogation responder system composed of a transmitter stationarily mounted in a certain fixed place and a receiver mounted on a mobile object. The receiver on the mobile side starts the operation when a power is supplied to the entire circuit in accordance with a wake-up signal from the transmitter on the fixed side so as to modulate the electromagnetic signal emitted from the transmitter on the fixed side in accordance with a predetermined code and reflect a response. This enables continuing bilateral communication of a command, data and so forth. By starting communication between the transmitter and the receiver by a direct wave of a carrier signal in a microwave band after sensing that the receiver on the mobile side has entered a good communication zone, secure communication is enabled at a sufficient electric field strength.

Abstract: An improved passive IFF system operating as a supplement to a conventional adar system including a coded variable delay system to produce like time-coded variable phase delayed identifying signal components indicative of cooperating or friendly objects and which overlap signals of other reflecting echo signals from the objects. The IFF system is provided with a retro-directive type antenna. The overlapping cooperating or friendly signal components and the corresponding other echo reflecting object signals are simultaneously detected at the radar system which is provided with a compensating or complementary phase delay means time coded in the same manner as the identifying IFF signal components. The identifying IFF signal components are thus produced in uniform phase and are summed up to provide a signal at the radar system whose magnitude is relatively large as compared to the combined corresponding echo reflecting signals which are in random-phase relationship.

Abstract: A method for assisting terrestrial vehicle traffic involves equipping at least some vehicles with a radar system and a transponder capable of re-transmitting with selected frequency transposition any radar wave received within a predetermined frequency band. The radar system semi-continuously transmits the waves capable of measuring a distance over a range of several hundreds of meter, and the radar system receives the transposed echoes in order to carry out distance measurement thereon. It is also possible to provide certain bodies, not equipped with radar, with individual transponders which are different from those provided on vehicles.

Abstract: The present invention pertains to a radiowave relay station in which image information or the like is transmitted by a helicopter from a first station to a second station. A direction finding device is provided which detects the direction of a transmitting source, i.e., a first station. The direction finding device calculates the vertical directional angle .phi. representing the direction of an incoming radiowave which is transmitted from the first station. This direction finding device allows the helicopter performing a relay function to fly rapidly to a contact point with the first station, i.e., in a vicinity of the first station. The direction finding device may also provide information to control an antenna driving portion for adjusting a receiving antenna located on the helicopter.

Abstract: A radar system operating by the line-of-sight method requires an accurate measurement of the relative position of at least two objects. By sending out coded radar transmission pulses, control data are transmitted to a guided flying body in a radar beam, which sends back an echo signal to the receiver via a transponder. In order to measure the passive signal and the transponder echo signal in the radar beam as accurately as possible, common reception channels are provided for both echo signals containing, inter alia, arrangements to equalize the dynamic levels of the echo signals. The returned transponder echo signal corresponds with respect to coding and bandwidth to the transmission pulses originally generated in the transmitter and that are phase-coded but not provided with the control code.