Abstract: A radar transponder and transponder system is provided for providing transponder communications signals embedded within radar interrogation and reply signals. The radar interrogation signals include transponder interrogation signals embedded within the bandwidth thereof. The transponders include a receiver for extracting the transponder interrogation signal and an offset frequency generator for up-converting or down-converting the transponder interrogation signal while remaining within the bandwidth of the radar signal. The transponders may be selectively enabled in response to interrogation signals having particular frequencies and/or in accordance with preset date or time schedules. The transponder outputs may be phase coherent with the interrogation signals and generated less than 10 nsec after receipt of the transponder interrogation signal. As such, the transponder reply signals are difficult to distinguish from the radar interrogation/reply signals.

Abstract: A covert and secure communication system which employs a very narrow bandwidth to permit receivers to be very sensitive to low power signals while maintaining acceptable signal-to-noise ratios. In the preferred embodiment, the system operates at the millimeter wavelength which, because of very high attenuation in atmosphere, will be undetectable beyond a very limited range. In another embodiment of the invention, the covert communication system is applied to an IFF system in conjunction with a homing missile. The IFF system of the present invention may be used as a back-up to confirm that a target is a foe by transmitting to and receiving a confirming signal from the target at the terminal portion of the engagement. For example, transmission between the target and missile may occur when the target and missile are less than 2,000 feet apart.

Abstract: The invention relates to the processing of the multiple paths in an interrogator station which, in response to a salvo of interrogations, receives responses in the form of pulses. The station comprises at least two reception channels. The responses to each interrogation of one and the same salvo are classified by order of appearance. A value of dispersion of the energies is estimated, for each channel and each salvo, on the responses having the same classification. Since the first classified response is, by assumption, considered to have arrived by a direct path, the following responses will be eliminated, on the grounds that they have been received after passing through multiple paths, if their values of dispersion of energy on the two paths are not equivalent to those of the first response.

Abstract: The combat communication system is used for "identification friend or foe", firing simulation during practice, and/or combat aiming for live night shooting. Each participant wears a harness comprising light detectors and control units, as well as a laser assembly mounted to a weapon. For firing simulation or identification, a participant aims his weapon at a potential target and sends a laser signal. When the target is another participant wearing a harness, his harness answers via a radio, ultrasonic or light signal. The carrier frequency of the response signal can be determined and transmitted by the querying unit over the laser beam.

Abstract: An optical identification friend-or-foe (IFF) system for vehicles comprises an active cooperative identification friend-or-foe (ACTIFF) system wherein a responder optical head is located on each friendly vehicle. That responder optical head comprises a number of small panels arranged in an array with surfaces of adjacent panels being at an angle to each other, the outer surfaces of the panels being coated with laser paint designed to emit radiation at one or more selective wavelengths when subjected to a suitable interrogation pump beam. Those selective wavelengths form an identification code for a vehicle. In operation, an interrogating vehicle would transmit a narrow well-collimated infrared (IR) beam towards a target vehicle causing laser paint on the coated surfaces to emit the selective wavelengths when subjected to that IR beam. These wavelengths can then be detected by the interrogating vehicle for identification purposes.

Abstract: When an IFF system interrogates a target aircraft and receives IFF reply signals, monopulse processing of the reply signals can provide more accurate determination of target azimuth. However, when reply signals have amplitudes close to noise or jamming levels, azimuth processing by non-monopulse techniques such as beamsplitting or center of gravity analysis can provide better accuracy than monopulse azimuth processing. Methods are described to enable adaptive selection of the type of azimuth processing to be employed. Such selection is based on active comparison of received signal magnitudes against monopulse sum and difference signal threshold values and a noise threshold value. Monopulse azimuth processing can thus be used at all times, except when non-monopulse azimuth processing is chosen by such adaptive selection.

Abstract: A compact infrared identification and communication assembly, including a transponder device and at least one interrogator device, is provided. Each device includes a housing having an opening therein through which light may be received or emitted. The opening has a spectral filter mounted therein which permits only a specific frequency band of incident light to pass into and out from the housing. A dichroic beam splitter is mounted in the housing, aligned with the spectral filter, for reflecting and transmitting separate selected portions of the specific frequency band. A photodiode is aligned with the beam splitter, thereby receiving light from one of the separate portions, for example the transmitted portion. The photodiode converts its received light into an electrical signal which is subsequently converted into a form which a user may easily understand, for example an LED display.

Abstract: An IFF system produces a challenge in which some or all of the anti-interference pulses that are inserted between adjacent bits of an encrypted message are replaced with "information pulses" that convey information which a decryption sub-system uses to decipher the encrypted message. To produce an information pulse that replaces a given anti-interference pulse, the system combines an information bit with the anti-interference pulse. The decryption sub-system recovers the information bit from the information pulse by comparing the state of that pulse with the state of the anti-interference pulse that it replaced. If the states of the two pulses are the same, the information bit is a zero and if the states differ, the information bit is a one. The information included in the information pulses may be, for example, an address that the decryption sub-system uses to select a cryptographic key from one or more stored tables of keys.

Abstract: A method and device for locating and identifying objects uses an encoding transponder in combination with the use of an SAR device carried in aircraft and spacecraft. Signals transmitted by the SAR device are received by the transponder are provided with an additional dominant signal structure and subsequently retransmitted back to the SAR device. Once the modulated code sequence is known, a signal correlation can be carried out between the signals output by the transponder and the signal reflected from the environment.

Abstract: A modulated retroreflection system for secure two-way communication and identification includes a transceiver at a first location and a transponder at a second location. The transponder receiving, modulating, and reflecting the signal back to the transceiver includes a retroreflector having a at least one reflective surface coated with an electro-responsive material. The electro-responsive material modulating the reflection coefficient of the reflective surface thereby modulating signals reflected by the surface. The transponder further includes a modulator electrically connected to the electro-responsive material for applying a modulated bias voltage thereby modulating the refractive index and consequently the electrical phase, and/or amplitude of the reflected signal.

Abstract: A deciphering unit having input and output matrices connected to a master ift register to permit flexible access to its stages. The output matrix allows selection of four register positions in the master shift register from which data is fed to a correspondence generator where it is partially descrambled. Subsequently, the input matrix allows selection of four input register positions for the partially descrambled data, and one input register position for serial key shift register data. A comparison matrix selects eight bit positions to allow comparison of the descrambled master shift register data with a predetermined eight bit word. Upon favorable comparison a four bit word is transmitted to a base interrogating station for identification. Also, the same apparatus can be used for enciphering by shifting the data in the master shift register in a reverse manner.

Abstract: The invention is an identification friend or foe system for an aircraft providing identification information when illuminated by an incident radar signal. In detail, the system includes at least a portion of the aircraft's surface incorporating magnetic material for absorption of at portion of the incident radar signal with the remainder reflected and scattered back in the direction of the incident radar signal. A electromagnetic coil assembly) is positioned behind the aircraft skin and is used to impress a biasing field on a portion of the aircraft's surface incorporating the magnetic material such that the biasing field modulates the reflected and scattered signal. A system is coupled to the coil assembly to modulate the biasing field such that the reflected and scattered signal from the portion of the aircraft's surface incorporating the magnetic material is modulated with an encoded signal incorporating the identification information.

Abstract: A post launch identification friend or foe fire control system for a munition has an identification and ranging interrogation unit for mounting on a munition. The interrogation unit transmits an interrogation unit which detects and verifies an incoming identification code from a remote transponder unit in reply to the interrogation code. The range of the remote transponder is determined and a decision signal is provided to the fire control circuit of the munition to enable it to avoid a friendly target; a transponder unit receives the rf carrier signal containing an incoming interrogation code from an interrogation unit on board a munition, validates the incoming interrogation code, and extracts a timing signal from it. An identification code is synchronously generated with the incoming interrogation code using the timing signal. The synchronized identification code is then transmitted back to the interrogation unit on board the munition to confirm the identification of the transponder unit and its range.

Abstract: An IFF system including an interferometric ultra-high resolution synthetic aperture (SAR) radar located on an aircraft and a respective transponder located on one or more ground targets which may be, for example, ground vehicles. Each transponder is responsive to RF pulses transmitted from the radar and includes means for generating an identification code which then modulates the radar return with a coded signal indicative of the target's identity. Upon receiving the signal from the transponder, the radar processes the signals in an interferometric moving target focusing (IMTF) mode and a high resolution SAR processing mode to provide signals indicative of both moving and fixed targets with ID data superimposed thereon. Target ID extraction apparatus also having the same identification code applied thereto is included in the radar signal processor and extracts the target ID by a correlation technique which is then displayed along with the radar image of the target in question.

Abstract: In a method for automatically identifying an unknown number of transponders, these transponders are put into a dead state by a collision signal transmitted by the reader. Then, each transponder generates its own random dead time and the transponder with the shortest dead time is the first to transmit its data to the reader, while the other transponders are put into an idle state. When the reader has completely received the data of the first transponder, the idle states of the other transponders end and they generate another dead time for themselves. The entire process is then repeated, i.e., the transponder with the shortest dead time transmits its data to the reader, etc. until all transponders have transmitted their data to the reader individually and successively.

Abstract: A synchronous communication targeting system for use in battle. The present invention includes a transceiver having a stabilizing oscillator, a synchronous amplifier and an omnidirectional receiver, all in electrical communication with each other. A remotely located beacon is attached to a blackbody radiation source and has an amplitude modulator in electrical communication with a optical source. The beacon's amplitude modulator is set so that the optical source transmits radiation frequency at approximately the same or lower amplitude than that of the blackbody radiation source to which the beacon is attached. The receiver from the transceiver is adapted to receive frequencies approximately at or below blackbody radiation signals and sends such signals to the synchronous amplifier. The synchronous amplifier then rectifies and amplifies those signals which correspond to the predetermined frequency to therefore identify whether the blackbody radiation source is friendly or not.

Abstract: An Identification-Friend-or-Foe System Using Variable Codes (IFF System) lizes variable codes and pre-selected encryption/decryption technology to querry potential targets as to their battlefield affiliation and also to identify itself as a friend to a potential attacker. The IFF System performs a querry by sending a narrow laser beam to the potential target which is accompanied or closely followed by a radio frequency (RF) wave modulated with encrypted identification information. If the potential target is also equipped with the IFF System and in possession of the valid code, then the received RF wave can be decrypted to reveal the potential attacker as a friend. The potential target, then, encrypts its own identification information using the same code and transmits it via RF wave to the potential attacker. Thus fratricides may be avoided.

Abstract: A liquid jet head for discharging liquid comprises a plurality of element boards each having electrothermal transducing elements to generate thermal energy for discharging liquid, and functional elements to drive the electrothermal transducing elements on one and the same board; and a circuit board having the wirings through which the functional elements input signals from or output signals to outside. Electrical connections are made so that the output signals from the element board are inputted to the adjacent element board through the circuit board. In this way, no connections are needed between chips in wire bonding to make the directions of bonding one-way, leading to a significantly increased efficiency of work on the wire connection.

Abstract: The harness comprises a plurality of elements, such as light detectors, a laser emitter and a master control unit. The elements are communicating by means of ultrasonic signals. Such signals provide a secure communication over a short distance while being impossible to detect from larger distances. Upon initialization of the harness, the master control unit initializes all elements to respond to a common identification code, which identification code can be updated automatically during later operation.

Abstract: An electronic system 8 is disclosed herein. The system includes circuitry 10 for processing a signal and a plurality of antennas 12a-12b. A plurality of switches 22a-22b are also included. Each of the switches 22a-22b is coupled between the processing circuitry 10 and a corresponding one of the antennas 12a-12b. Each of the switches 22a-22b includes first and second power MOSFETs where the source of the first MOSFET is coupled to the source of the second MOSFET. The system further includes circuitry 28 for selecting of one of the plurality of switches 22a-22b to be on.

Abstract: An optical identification friend-or-foe (IFF) system for vehicles comprises a Selective Wavelength IFF (SWIFF) system with a tunable optical beacon being located on each similarly equipped vehicle. That tunable optical beacon includes a light source and wavelength encoder which can select a number of narrow-band optical wavelengths for emission from the beacon, those selected wavelengths forming an identification code for a vehicle. The optical beacon directs the selected wavelengths along an optical path to a diffuser which can irradiate a wide field-of-view around the vehicle with those selected wavelength for detection and identification by other friendly vehicles. The light source may be one that emits a broad range of wavelengths with the encoder providing a number of narrow-band optical filters which can be selectively positioned in the optical path from the light source to the diffuser.

Abstract: The disclosure relates to the recognition of an objective known as an IFF or "Identification Friend or Foe" system. In the interrogator unit of the IFF system, the signals received undergo processing operations that take account of the characteristics of the antenna and enable the useful information to be separated from the disturbances. In order to be able to use an electronic scanning antenna in spite of the fact that it has characteristics which vary with the training angle, hence with the direction in which the objective is located, the processing operations to be performed are designed for different training angles, the characteristics of these processing operations are memorized and the processing operations are performed as a function of the training angle.

Abstract: A night vision device includes an image intensifier tube for providing an intensified image of a dim or night-time scene. The night vision device also includes provision for full duplex transmission and receipt of voice audio between the user of the device and another person who is using a substantially identical device. Another provision of the device is for interrogating IFF (identify friend or foe) units worn by other personnel. The IFF units have provision for receiving a beamed interrogation signal and for transmitting a coded identification signal in response. Thus, a user of the night vision device can identify friendly personnel at a distance, as well as communicating by voice with others who are using similar night vision devices so equipped.

Abstract: A method and apparatus for passive identification includes a series of elements preferably in the form of strips, bars or other geometric shapes, or as dipole antennas made of a material having variable EM retro-reflectivity characteristics. By varying the characteristics of individual elements (i.e. spatial, polarization, frequency response and angular extent of retro-reflection), the elements form an alterable pattern which can be used for identification. The characteristics can be changed remotely, the ability of the device to understand and implement the change being a criterion for identification.

Abstract: Apparatus and method for conveying information from an object by delayed reflection of an interrogating ultra-high range resolution radar signal which is digitized into a series of programmable spaced pulses by an electronic license plate circuit. The electronic license plate includes a plurality of unique programmable delay lines connected through a coupler network to an antenna.

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 optical retroreflector apparatus and method detects (20) incident light radiation (12). A processor (30) periodically enables the detector (20, 60-64) to receive a signal included in the incident light radiation (12). A reflector (40) is triggered by receipt of a particular signal included in the incident light radiation to reflect a coded signal toward the source of the incident light radiation.

Abstract: A method of protecting a predetermined area, comprises the steps of: a) providing a base station positioned essentially at the center of the area to be protected, the said base station being provided with scanning laser beam generating and receiving means, image and signal processing units, memory means, voice receiving and transmitting means and image viewing means; b) causing a laser beam generated by the base station to be reflected from the surveyed area into the receiving means of the base station; c) processing the received reflected light to generate an image of the surveyed area; d) storing one or more scanned images in memory means, to be used as reference images; e) at any given time, comparing a real-time scanned image with one or more stored reference image(s), to determine changes which have occurred on the image, which exceed predetermined threshold values, and alerting the operator of the base station of any such changes; f) providing one or more moving station(s) comprising emitting/receiving

Abstract: A system (10) for friend-or-foe identification (IFF) comprises an interrogator unit (18) carried on a first platform (T1) for generating and transmitting a laser beam. A control unit (22) selectively directs the transmitted laser beam toward a second platform (T2). A coding/decoding unit (28) encodes an IFF interrogator message with which a portion of the transmitted laser beam is modulated. A laser reflector (30) carried on the second platform receives the coded laser beam. The reflector is a normally passive reflector which is activated by receipt of the transmitted laser beam. The reflector responds to the IFF message contained in the received laser beam by modulating the unmodulated portion of the transmitted laser beam. This newly modulated portion of the laser beam is reflected back toward the first platform. The coding/encoding unit decodes on the first platform receives and the response, and determines if it corresponds to a predetermined response which identifies the second platform as a "friend".

Abstract: A transponder receives a stable reference frequency transmitted from an interrogator and compares the stable reference frequency to a local oscillator frequency that has short term stability. A comparison signal is provided to a synchronous oscillator for providing a locked signal that briefly locks onto the comparison signal and "remembers" its phase and frequency characteristics. The locked signal, which is inherently locked to the stable reference signal of the interrogator, is then combined with the short-term stable local oscillator frequency, and the combined signal is used in the up-converted reply back to the interrogator.

Abstract: Apparatus and method for allowing ground vehicle identification and communication utilizing IFF equipment consisting of a multi-channel extremely high frequency transmitter for IFF and data transmissions and a receiver for multi-frequency conversions and multi-channel reception. The apparatus and method has both an IFF mode of operation in which the vehicle is able to identify itself and a communications mode in which the vehicle transmits vehicle status information to other vehicles and a command unit. The transmitter comprises a first and second oscillator means for generating a number of frequency tones and a power combiner for combining the tones prior to transmission. A controller monitors the transmitted signal and operates the first and second oscillation means. The receiver consists of a channelizer for separating a received signal into separate frequency tones and a measuring means for determining the values of the frequency tones. A controller controls the comparison or decoding of received signals.

Abstract: To harden transmissions, in both directions, between a master station (1) and a slave station (2), a table of communication parameter values is memorized in each station and the table values are then used in accordance with the master station's decision. Each message from one station to the other contains information to allow the receiving station to determine the parameter values to be selected in the table to eliminate values where there is a high risk of jamming.

Abstract: A semiautomatic jam-accept decider for use in an interrogator responsor installation in which an operator selects a particular range and azimuth of interest. The decider can make Accept decisions concerning IFF Mark XII Mode 4 reply targets in the presence of extraneous signals. Enemy spoofing or jamming of the Mode by transmitting on the reply frequency can also be detected and the position of the enemy aircraft can be determined.

Abstract: A laser interrogator system and technique establishes low-observable idenication friend or foe (IFF) between two distinct positions. An interrogating laser transmits a laser pulse from a first position to a passive retroreflector fiber optic bundle located at a second position. The bundle retransmits a delayed laser retroreflector pulse. A receiver and processor at the first position processes the received retroreflected delayed laser pulse to determine a presence of a predetermined delay such that an IFF determination of the second position is achievable.

Abstract: An Identification Friend or Foe (IFF) system uses CO.sub.2 laser identification beacons on ground vehicles such as tanks, in conjunction with an existing (or future) Forward Looking InfraRed (FLIR) detection system on an attacking aircraft or ground vehicle, to provide a cost effective solution to the problem of identifying friendly targets on a battlefield. The CO.sub.2 Laser can produce radiation only in the FLIR's spectral band, aiding stealth and improving signal to noise ratio. An acousto-optical modulator in conjunction with a specially shaped optical reflector steers the beam in the desired direction toward the FLIR in the attacking aircraft, aiding stealth and detection signal to noise ratio. The optical element also shapes the beam into the desired angular extent, needed for reception by the attacking aircraft.

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: Received IFF reply-frequency signals are examined to determine whether they re being interfered with by enemy sources, and indication of the extent of detected interference is provided.The number of correct replies received from selected range bins surrounding and including the center one in which a target leading edge is first declared is counted and compared with the count of the number of friend-accept decisions made based on replies from the selected range bins. The level of interference is then indicated by the ratio between the two counts.

Abstract: Systems are provided for distinguishing between friendly ground targets and those of a foe and for receiving passive communications from friendly ground targets by providing friendly ground targets with reflector means adapted to modulate or otherwise change the character of laser light striking the reflector surface. The target is illuminated with a laser beam and the reflected laser energy is examined to determine whether it differs in character from that normally reflected from a target. Modulation of the laser beam can be accomplished by changing the reflectivity of the reflector means according to a selected sequence or pattern.

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: An IFF device comprises a beam generator for directing an unmodulated beam at a target. The target has a plurality of retro-reflectors mounted on it. These retro-reflectors have internal reflecting surfaces for reflecting the unmodulated beam penetrating the retro-reflector. A device is associated with the internal reflecting surfaces for modulating the beam at a predetermined frequency so that the reflected beam emerging from the retro-reflector is modulated at the same frequency. A tuner is positioned in the path of the reflected modulated beam and tuned to predetermined frequency, so that if the tuner receives a signal, it indicates the target is friendly.

Abstract: A microwave carrier signal emitted from a tracker unit is amplitude moduld periodically at different preset modulation frequencies during spaced intervals between established time slots. The carrier signal is detected by differently coded credential units within a reception zone whereby such signal is demodulated at the different modulating frequencies to produce reply signals at one of several different code frequencies during one of the time slots dependent on the credential unit coding. The reply signals are detected by the tracker unit during narrowed reception windows within the time slots. Such reply signals are decoded within separate frequency channels corresponding to the code frequencies thereof to extract signal data processed to indicate entry, departure and status of the credential units relative to the reception zone.

Abstract: An enemy radar or transmitter transmits a signal at frequency f1. A tag on a friendly forces target receives frequency f1 and, in response thereto, transmits a signal at frequency f2.noteq.f1 modulated by a code unique to the tag. A friendly forces receiver, in response to receiving frequency f2 provides an indication that (a) the tag has received frequency f1, meaning the enemy is operating in the area, and (b) which specific tag has received a signal at frequency f1. The friendly forces can then take appropriate action.

Abstract: A universal IFF technique and system utilizes a real-time communication l established between both parties allowing the approximate immediate transferral of digital information with positive direction and identification of both parties achieved. A pump laser emits a first signal at a first position and a remote laser beacon emits a second signal at a second position, both signals at nominally the same wavelength. A MPPCM receives the first signal which establishes a beam fan. The MPPCM and first signal scans about a region of interest to intercept the second signal. The second signal provides a second input signal into the MPPCM so that a two-way phase conjugation signal builds up and lock-on is established.

Abstract: A compact beacon-detector type IFF system to be carried by individual soldiers. The system consists of a beacon and a special purpose detector. The beacon is a small, light-weight, battery powered device that is worn on the soldier's web gear. The detector consists of a small flashlight-like device that can be hand held or mounted on a weapon, similar to a rifle scope. The beacon's signal is not visible to those using existing night vision equipment nor is it otherwise exploitable by a potential adversary. The system achieves its covertness through the selection of the optical wavelength used by the beacon. Further signature reduction is achieved through the use of a Low Probability of Intercept ("LPI") spread spectrum waveform as the beacon output. This waveform utilizes a spreading code to encode the beacon output signal.

Abstract: An Identification Friend or Foe (IFF) method and system are provided to dct i) friendly ground-based vehicles, ii) each of the vehicle's unique identity, and iii) each of the vehicle's approximate position. A video image of an area of interest on the ground is generated from an aircraft. The video image is defined by a matrix of pixels. A range from the aircraft to a reference position within the area of interest is provided. The reference position is defined by known latitude, longitude and height within the area of interest and is further defined in the matrix of pixels by matrix coordinates. A coded signal is transmitted from a vehicle on the ground to uniquely identify the vehicle and identify the vehicle as friendly. The coded signal is also detectable as part of the video image when the coded signal is transmitted from the area of interest. The vehicle position within the area of interest is thus defined in the matrix of pixels by matrix coordinates.

Abstract: A laser warning receiver (LWR) having an ability to not only detect a low power level laser source, such as a pulse train emitted by a laser beam rider, but to also provide a high angular resolution in determining the angle of arrival of that pulse train. The receiver includes a lens/filter arrangement for a large area photodetector to detect an incoming signal from an emitting source and a high gain amplifier to amplify the signal which is then applied to a synchronization generator that generates a digital pulse train with pulses corresponding to peaks in the incoming signal. The digital pulse train is applied to a code breaker where the code is analyzed and a further code is generated anticipating the arrival of further pulses in order to verify the code. That further code is applied to a time gate generator which generate a code, synchronized with the incoming signal, that controls the high voltage of a gated image intensifier which is coupled to a video camera.

Abstract: An identification friend-or-foe system for vehicles wherein each vehicle is provided with a radiation transmitter and a receiver with a detector for detecting radiation transmitted by other vehicles. Each transmitter can transmit a first coded signal which can be detected by the receivers in other vehicles, the receivers providing an unblocking signal after the first coded signal is correctly identified. The unblocking signal clears a radiation transmission path in the vehicle, the path containing a reflector which reflects the received signal back to the source of the transmission. The reflector adds a further predetermined code to the signal reflected from the reflector with each vehicle having another detector for detecting a reflected signal and a device to identify the further predetermined code.

Abstract: A system for locating and identifying aircraft while on an airport. Each aircraft has an IFF transponder which is interrogated from on board the aircraft to produce replies at a slower rate than normal interrogation rates. A plurality of receiving stations at different locations about the airport measure the time of arrival of the replies and decode the replies. The time of arrival information is forwarded to a central receiving station along with the decode reply data. Using conventional correlation techniques, the location of each aircraft is established through the time of arrival information as well as the identity of the aircraft from the decoded reply data.

Abstract: An electronic identification system for use by vehicles on a battlefield comprises an interrogator circuit in an attack vehicle and a transponder circuit in several other vehicles which are friendly but could be mistaken for the enemy. In operation, the interrogator circuit transmits a time shifted code which is very difficult for an actual enemy to detect and/or jam, and which causes the transponder circuits to send a response from only a selected one of the other friendly vehicles that is being examined by the attack vehicle as a target.

Abstract: A method of and an apparatus for positively identifying the vehicles, troops, and landmarks of friendly forces to reduce or eliminate the threat of fratricide includes a light display comprising a plurality of flexible electroluminescent panels which are conformable with and affixable to visible outer surface of friendly or noncombatant vehicles, troop helmets, or landmarks. Each of the panels is electrically energized and modulated under computer control to provide various combinations of pattern display, color, intensity, and activation times to transmit a desired identification code.