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 and apparatus for preventing unauthorized sources from utilizing rcraft-borne I.F.F. for locating same. A bypass switch is inserted in the I.F.F. transponder antenna line which normally sends all incoming signals into a dummy load. Upon receipt of a proper interrogate command, the antenna is switched to the transponder.

Abstract: A friendly target recognition system is provided for use in combat zones ing friendly and unfriendly target objects residing therein. Transmitting means are mounted on each friendly target object in the combat zone to transmit radiation in the form of coded, short burst data packets according to a particular digital transmission code sequence. A receiving means is mounted on the targeting device that is aimed at one targeted object. The receiving means has a field-of-view that is limited to the one targeted object such that the presence of the transmitted radiation according to the particular digital transmission code sequence is indicative of a friendly target object.

Abstract: An identification of friend from foe (IFF) device is described containing a radio transceiver (F) which, in addition to being designed for communication purposes, is equipped for transmitting, receiving, and evaluating IFF signals. The IFF device further includes a laser transmitter (LS) and an optical receiver (LE) which are coupled to the radio transceiver (F) via a controller (G). For identification, unmodulated direction-selective light signals and modulated nondirectional radio signals are used.

Abstract: An antenna system for mounting in a roadway comprised of an electrically lossy material. The antenna system has a reflector trough shield filled with a solid dielectric. An antenna, preferably comprised of coaxial cable, is positioned in the reflector trough, which prevents electromagnetic waves radiated by the antenna from being lost into the roadway.

Abstract: An electro-optical IFF system easily integrable into existing laser systems uses a laser to illuminate a potential target platform. The potential target, if friendly, has apparatus for returning to the illuminating platform a return beam which has the same signature but is delayed with respect to the illuminating beam by a predetermined time interval. If the illuminating platform sees a return beam with the same signature in the proper time frame, an indication is generated that the target is friendly. A friendly target platform contains apparatus for comparing the signature of the illuminating beam to a stored reference signature, and for providing a friendly-illumination indication and activating the return beam only if the signatures match.

Abstract: An IFF system comprises an interrogation device having an antenna arrangement operating in the HF or microwave range with a relatively broad radiation characteristic for radiation of coded interrogation pulses and for receiving answer signals. The IFF system cooperates with a position finding device whose transmission pulses are radiated by way of a relatively narrow radiation lobe and wherein the answer signals are triggered in the answering device in response to the arrival of transmission pulses of the position finding device.

Abstract: A system for secure distance ranging between a reader 11 and a tag 12 wherein the distance between the two is determined by the time it takes to propagate a signal from the reader to the tag and for a responsive signal to return, and in which such time is random and unpredictable, except to the reader, even though the distance between the reader and tag remains the same. A random number (19) is sent from the reader and encrypted (26) by the tag into a number having 16 segments of 4 bits each (28). A first tag signal (31) is sent after such encryption. In response, a random width start pulse (13) is generated by the reader. When received in the tag, the width of the start pulse is measured (41) in the tag and a segment of the encrypted number is selected (42) in accordance with such width. A second tag pulse is generated at a time T after the start pulse arrives at the tag, the time T being dependent on the length of a variable time delay t.sub.

Abstract: The device is an IFF Authentication System for sending and receiving of coded intelligence. So as to reduce an alien's chances of using the intelligence transmitted, the system uses a clock to provide signals for additional encipherment or scrambling of the coded intelligence. The clock is easily synchronized and provides continuously changing code encipherment for maximum protection and is connected into the system at a variety of predetermined places depending on the componential design of the particular system being used.

Abstract: A radar system, such as a tracking radar installation or other radar installation which is of the pulse compression type, transmits data during transmission of the radar signal. The data is transmitted by inserting, into the radar signal, at least one short nonpulse interval. The position of the nonpulse interval within the radar pulse can be modulated.

Abstract: This method can be used either as an independent radar system or as an adct to an existing radar system, after suitably modifying the existing system, and will provide a cooperative, Radio Frequency passive, identification system for either stationary or moving targets. The system uses suitable devices that will mechanically vibrate as a transponder mechanism as an attachment to stationary or moving targets. A sideband analyzer is used to identify the viberation pattern in the radar return, and therefore, identifies the target.

Abstract: Apparatus and methods for combining incoherent signals having different carrier frequencies but a common modulation to obtain a coherent summation of the modulations of such signals are described. The apparatus comprises adaptive means of changing the carrier frequencies and corresponding phases of various signals to a common carrier frequency and a common phase, thus enabling the coherent summation of the common modulation and enhancing, thereby, the level of received information content. When the incoherent signals are transponder-signals, radiated from an object or platform in response to a modulated interrogating signal, and are obtained by different frequency offsets from the interrogating signal carrier frequency, the particular offset frequencies being unique to that object or platform, the ability combining of modulations coherently provides a means of unique identification of the object or platform.

Abstract: A reply decoder (30) for declaring mode 4 replies when used with a KIR cryptograph computer (25) is described including timing logic (114), memory (112) for storing mode 4 replies and logic circuitry for analyzing replies stored in the memory (112). The invention further provides logic circuitry for detecting railing (117) i.e., successive replies, for detecting garbled or overlapping replies (123), for providing a floating density value window (114, 120) for summing the replies in nonselected reply positions and for target start/stop determination (215) based on selected criteria. The invention overcomes the problem of declaring excessive mode 4 replies which over burden the subsequent reply processing in a reply processor (50).

Abstract: An IFF system interrogating station comprises an IFF interrogator which has its transmission antenna joined to the infra-red camera of a field observation device. Each friendly vehicle is fitted with an IFF receiver antenna and an infra-red laser transmitter transmitting a laser pulse at each IFF interrogation.

Abstract: A method of providing secure tactical communications between a submerged submarine and an airborne platform using a pulse-modulated blue-green laser beam. During an initial acquisition mode, the airborne transceiver sends out a downlink laser beam to the ocean surface and below using a predetermined IFF code to identify the transceiver to the submarine. In the preferred embodiment the transmit optics spread the beam out into an elongated elliptically-shaped pattern to maximize coverage of the search area. When the downlink beam energy is within range of the submarine, an optical receiver on the submarine detects the beam, filters out the background light with a very narrow-band filter, and converts the light pulses to equivalent electrical pulses. A signal processor in the submarine receiver decodes the electrical pulses and verifies the IFF code to prevent the submarine from responding to a laser beam from an unfriendly source.

Abstract: An identification system to identify objects from a remote interrogation station may be used with moving objects such as railroad cars. The system remotely programs and stores information on an object and remotely retrieves information from the object. An information and identity storage device is located on the object and at least one interrogation station is located remotely from the object.

Abstract: Diclosed is a dual band communication receiver for use in a burst communication sytem. The receiver is capable of esentially simultaneous reception at a first carrier frequency (L), such as L-band and a higher carrier frequency (H), such as S-band, using distinct codes and replying in the frequency band received. A typical system is composed of a transponder and an interrogator. The incoming coded signal is down converted to an i.f. frequency compatible with surface acoustic wave (SAW) convolvers. The i.f. signal is then divided between two SAW convolvers, each having a convolution interval of two times the message symbol length (2T). Reference signals A and B are composite signals comprised of alternate L-band and H-band signals, each having a time period equal to T and each L- or H-band signal operating at a 50% duty cycle. Reference signals A and B are time reversed to the input signals applied to the convolver and are orthogonal to one another.

Abstract: Disclosed is a communication receiver for use in a burst communication system. A typical system is composed of a transponder and an interrogator. The transponder receiver and interrogator receiver operate in an asynchronous communication mode. The incoming coded signal is down converted to an i.f. frequency compatible with surface acoustic wave (SAW) convolvers. The i.f. signal is then divided between two SAW convolvers, each having a convolution interval of two times the message symbol length (2T). Reference signals having a bit length of T provided to each of the two convolvers are time reversed to the coded spread sequences and applied to each of the convolvers at a 50% duty cycle. Each of the convolver outputs are processed through log video detection circuits to reduce the dynamic range followed by peak detecting and stretching to reduce the pulse bandwidth.

Abstract: The IFF system uses basic identification codes which are transmitted between an interrogator and a responder. The basic codes are chosen in dependence upon the time and position of the interrogator or responder at the time of choice. In one version of the system, the lifetime of a code is less than or equal to the propagation time of a radio signal for a given maximum range between the interrogator or responder. Interactive interrogation may also take place using codes chosen in the same way as the basic codes. Local information may also be transmitted between the interrogator and transponder. An example of apparatus for performing these operations transmits basic or other codes together with a time code defining the time of production of the basic or other codes. It is not essential to transmit a time code in some circumstances. Position and time information may be gained from an external communications system.

Abstract: The invention pertains mainly to a method and a device for the display of targets and/or target positions using the data acquisition means of a weapons system.The device of the present invention can be used to display the target or the direction of the target acquired by missile homing heads. This data comes as a complement, and other data on the position of the target is used to ascertain that the homing head is properly locked on as well as to supplement any lack of information caused, for example, by a breakdown in the display systems. The invention can be applied mainly to the building of anti-aircraft defense launching platform or anti-aircraft and anti-tank launching platform.

Abstract: A secure identification system for identifying a potential target in a battlefield environment as being either a friend or a foe is disclosed. An interrogator produces two interrogation pulses, such as laser flashes, aimed at the target and separated from each other by a randomly determined period of time. The target detects the two interrogation pulses, measures elapsed time between the two pulses, and prepares a reply signal for transmission which is controlled by the elapsed time. Frequency, pulse width, and transmission delay parameters are each controlled in a substantially random, but predetermined manner in response to the elapsed time. The interrogator has a receiver and qualifier which receive reply signals and define expected values for the controlled parameters. An indication is provided concerning whether the target represents a friend or a foe based on received reply signals at the interrogator.

Abstract: For carrying out an interrogation a position modulated laser light wave is used. A key word is displayed in an interrogator and coded in accordance with a cyclic code, for example Golay's code. This coded key word is used for modulating the laser wave. In the responder the same key word is displayed and coded in the same way. After reception and demodulation each message is compared in a correlation circuit with the local reference word. The correlation method used allows parasite pulses to be taken into account and the word received to be validated with a given security threshold.

Abstract: Test equipment is described for testing a transponder and an interrogator positioned in close proximity to one another to cause suppression of its receivers while either transponder or interrogator is transmitting incorporating an RF receiver, detector, shift register, timing controller, modulator and RF transmitter. The invention overcomes the problem of testing an interrogator and transponder with cryptograms that must be generated or stored in the test equipment and overcomes the problem of requiring two test sets for testing the interrogator and transponder.

Abstract: The process for limiting traffic according to the invention comprises an AND input gate receiving the incident pulses representative of the interrogations of the system, its output being connected to an authorization output as well as to a counter which is itself connected to an adder and to a counter, the adder receiving from a memory criteria values, and its output being connected via a reference values memory to the comparator, the output of which is connected via a memory to the said AND gate.

Abstract: The conventional way of achieving an identification, friend or foe (IFF) function for a moveable subject requires the subject to carry a transponder that emits a coded return when a radar pulse is received by its receiver. In the present invention, an IFF system is disclosed which departs from the conventional transponder method and employs no radio-frequency power source. Instead, it uses the scattering or reflecting properties of an antenna to modulate, in a distinctive manner, the radar return from a moveable subject. A binary sequence code generator modulates the impedance of a receiver antenna, with the reflected signal being detected and correlated with a synchronized code sequence at the radar.

Abstract: A multichannel DME ranging circuit is described which is capable of simultaneous multistation operation. A microprocessor is coupled to control associated peripheral devices and the receiver/transmitter of a DME to produce a multiplexing for receiving frequency data input from up to three DME ground stations. The data received from each of the three DME stations is used to generate timing and interface signals to control the DME receiver/transmitter and associated video processing circuitry. The video processing circuitry is in turn used to provide signals to the ranging circuit to independently determine range, velocity, time-to-station, and the identity of each of the stations providing input to the DME. Each of the three channels is constructed so that it may operate independently of the others to produce rapid acquisition, search, track and identification of each of the particular ground stations to be monitored.

Abstract: A precision distance measuring equipment (DME/P) receiver for detecting an RF signal including at least one interrogation pulse is described. The DME/P receiver includes first and second signal processing channels. The first processing channel includes a wideband filter, of bandwidth BW1, for receiving the processed RF signal and in response thereto generating a wideband (FA) mode signal proportional to the logarithm thereof. The second signal processing channel includes a narrowband filter, of bandwidth BW2, for receiving the processed RF signal and in response thereto generating a narrowband (IA) mode signal proportional to the logarithm thereof, the bandwidth BW2 of the narrowband filter being within the bandwidth BW1 of the wideband filter.

Abstract: A simple active/passive proximity warning system for an Own station that uses differential time of arrival values, direct time of arrival values, and differential altitude values determined from 1030 MHz interrogations from ground-based SSRs and Own station and 1090 MHz transponder replies from Other stations to identify threats is disclosed. The invention combines a passive detection system and an active detection system into an integrated system that overcomes the limitations present when either type of system is used by itself. Generally speaking, the passive system identifies threats and produces a threat alert when the differential altitude value and the largest time of arrival value associated with an Other station are below predetermined values. A preferred embodiment of the active system monitors the environment for SSR density, classifies the environment into a plurality of "cases", and automatically selects in response thereto one of a plurality of control modes.

Abstract: An improved bracket decoder apparatus including an enhanced bracket decoder ortion and a regenerative bracket decoder portion operates to generate enhanced bracket decode signals and regenerative bracket decode signals. The foregoing combination of decoder portions will allow digital display systems which use IFF information to detect all targets that are replying regardless of the IFF train spacing, even overlapping replies. The enhanced bracket decoder portion of the apparatus can be operated alone to detect all reply conditions except the one of overlapping replies. The apparatus is configured to provide presently used signals also, i.e., the bracket decode, the degarbled bracket decode, and the range and code information for each video reply.

Abstract: A 360.degree. IFF video resynchronizer unit for storing pertinent data such s the range, the code, the IFF mode and the azimuth for each reply from associated transponders is disclosed. The 360.degree. IFF video resynchronizer unit is also configured for interfacing with one of a plurality of interrogator subsystems associated with a plurality of radar systems having multiple antennas so as to backup any one of the plurality of interrogator subsystems with a single 360.degree. IFF video resynchronizer unit. In addition, any number of the plurality of interrogator subsystems can be replaced with a single 360.degree. IFF video resynchronizer unit when at least one of the plurality of interrogator subsystems is present.

Abstract: A converter, according to the present invention, operates to convert pertnt IFF data which is in a digital format to an IFF composite video format. The converter is configured to interface with conventional plan-position indicators (PPIs) and decoders.

Abstract: A collision avoidance system for aircraft in which one aircraft is equipped with an interrogation station having a secondary surveillance radar. .[.Coarse.]. .Iadd.A .Iaddend.distance measurement is effected either by passive or active distance measurement or by both of them. If the detected distance lies within a certain limit, the output power and/or period of the interrogation signal of the secondary surveillance radar of the subject aircraft is altered .[.so as to effect fine distance measurement.].. This system can be applied without increasing interference against the existing secondary surveillance radar system by keeping the output power and period of interrogation signal in a minimum required extent. By the same reason the system can keep the interference at a small extent between proximate aircraft, each mounting this collision avoidance system.