Abstract: A balanced receive antenna circuit configuration determines an accurate position of a transponder within the antenna field pattern of the reader antenna. The balanced receive antenna configuration consists of two antennas physically rotated 90 degrees relative to one another, disposed concentrically on top of one another. Furthermore, each receive antenna consists of two coils located a predetermined distance apart. The optimum distance separating the coils is determined by trading off zero position detection with the transponder detection range. A third receive reference antenna is concentrically disposed, sharing the same horizontal plane with the balanced antenna coilsets. The transmitter antenna is disposed separately from the receive antennas. In operation, initially the transmitter antenna sends a power burst signal for a predetermined duration to charge up the transponder to the maximum charge possible.

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: In a remote identification device, an interrogator sends a microwave signal to a responder, the interrogation wave signal being modulated. At each period of the modulation signal of the interrogation wave signal, the responder accumulates the energy conveyed by this signal, the energy received being converted into supply voltage to be used to encode and transmit a response microwave signal to the interrogator. This may be used for the identification of objects by a radar signal.

Abstract: An improved inductor/antenna (100)improves the selectivity of a recognition system (10) by ensuring that only the transponder (14) closest to the inductor/antenna (100) of an interrogator (12) receives therefrom, and reacts to, an interrogation signal (S1). The improved inductor/antenna (100) also receives the resulting recognition signal (S2) from the transponder (14) for analysis by the interrogator (12). The inductor/antenna (100) includes two or more coils (102, 104; 124, 126, 128, 130; 132, 134) which may be wound on ferromagnetic cores (108), spaced around a metal mass (46, 48) such as a lock cylinder (46) of an ignition switch (24). The shape, number, location and relative winding sense of the coils are selected to shape and locate the energy field (F; 118, 122) radiated by the inductor/antenna (100) so that only the transponder (14) in a key (26) which is inserted into or operating the ignition switch (24) responds to the interrogation signal (S1) radiated by the inductor/antenna (100).

Abstract: The invention relates to an identification system comprising an interrogator and a plurality of transponders. The interrogator includes transmitter means for transmitting an interrogation signal to the transponder, receiver means for receiving a response signal from the transponder, and processor means for identifying the transponder from data in the response signal. Clock extraction means are further provided for extracting a transponder clock signal from the response signal which is used to synchronise the modification of the interrogation signal with the response signal from the transponder. Each transponder comprises receiver means for receiving the interrogation signal, a transponder clock generator, a code generator, transmitter means, and a modulator connected to the code generator, so that on receipt of the interrogation signal the transponder transmits a response signal containing data which identifies the transponder.

Abstract: The present invention uses a novel adaptation of a tree splitting algorithm applied to Radio Frequency (RF) tagging technology to identify many tags in the RF field of a base station.The invention uses the tree splitting algorithm to identify a single tag in a field of a plurality of radio frequency tags. Once the single tag is identified, the identified tag is placed in a Data.sub.-- Exchange state where the base station can access data from the tag memory by using information that identifies the tag.

Abstract: A method for interrogating remote transponders having the steps of: sending an RF interrogation pulse from an interrogator (10), receiving by a first and second transponder (12,12a) the RF interrogation pulse, and establishing in a resonant circuit (130) of each of the transponders (12,12a) an oscillation, the oscillation being established by the coupling of signal energy from the RF interrogation pulse into the resonant circuit (130). After the RF interrogation pulse ends, the first transponder (12) senses the termination of the pulse and initiates a first RF response having a selected duration. A second RF response from the second transponder (12a) will also be detected in the first transponder (12) whose response will be affected by this second RF response.

Abstract: A transponder arrangement is described having an interrogator unit (10) which transmits at least one RF programming sequence and at least one RF interrogation pulse. The responder unit (12) includes a responder unit receiver (130) for receiving data transmitted by the RF programming sequence from the interrogator unit (10). The responder unit (12) then upon receipt of the RF interrogation pulse transmits data, which may have been modified by the programming sequence from the interrogator unit (10), back to the interrogator unit (10) in the form of a modulated RF carrier. The responder unit (12) further comprises a responder unit energy accumulator (136) which stores energy contained in the RF interrogation pulse and a responder unit end of burst detector (142) which upon detection of a decreasing power level of the RF interrogation pulse sends a RF threshold signal.

Abstract: In a method for transmitting a data message comprising a synchronization section and a data section stored in a transponder device (10) to an interrogating device (12) in full duplex mode. The interrogating device (12) continuously emits an interrogating command, the receipt of which in the transponder device (10) prompts output of the data message. Both the sync section and the data section of the data message each comprise a predetermined number of bits in accordance with a given transmission protocol. In the sync section, a predetermined number N of sequential bits of duration .tau. is replaced by a lesser number n of sequential bits of longer duration T, where: T=.tau. N/n. The interrogating device (12) determines the location of the sync section and thus the start of the data section in the received data message by identifying the bits having the longer duration T. For the ratio N/n a value is selected which is smaller than 1.5.

Abstract: The monitoring assembly (10) monitors the location of mobile objects (12), i.e., personnel, within a structure (18). The object (12) carries a transponder (14) which periodically transmits status signals and receives command signals. Transceivers (16) are fixed at locations about the structure (18) for receiving the status signal producing the location signals, and transmitting commands to the transponders. The transmissions and reception occur during prescribed time windows. A central controller (20) is connected to each transceiver (16) and monitors the location of transponders (14) and communication therethrough. The transponders (14) have audio capability of producing audio messages directly to the person thereof, especially during emergency conditions for assistance. The controller (20) transmits synchronizing signals to the transceivers (16), which in turn synchronize themselves and transmit the synchronizing signal to the transponders (14) for synchronizing.

Abstract: A Radio Frequency Identification (RFID) system having an interrogator (12) and a transponder (14). The interrogator has a first tuned circuit (28) of a powering frequency for sending a powering burst to a transponder (14), a filter/demodulator (64) for receiving an wireless, modulated RF response from a transponder (14). The interrogator (12) further has a second tuned circuit (29) in electrical communication with a modulator (48), the second tuned circuit (29) having a selected bandwidth about a communication frequency, the selected bandwidth not substantially overlapping the powering frequency and encompassing the bandwidth of the modulated carrier of the RF response.

Abstract: A signal received by an electronic article surveillance system is processed using a neural network processing algorithm to determine whether an electronic surveillance marker of a predetermined kind is present. The raw received signal is processed to generate a small number of parameter values to be provided as inputs for the neural network. The neural network processing distinguishes between two different types of surveillance marker.

Abstract: A system and method for avoiding the discharge of a battery or otherwise excessive power consumption by a transponder (14) in the presence of a spurious noise source. In a described embodiment, the transponder (14) renders itself immune to activation by presence of RF energy for some period if the transponder does not receive a proper wake-up message within an activation period.

Abstract: A transponder interface circuit (172) operates to allow communication between a transponder controller (104) and external circuitry. The interface circuit (172) has a buffer memory (184,186) that allows the transponder controller (104) and the external circuitry each to transmit data at either the transponder's (14) or the external circuitry's clock rate without complicated protocols for direct communication. Each of the transponder controller (104) and the external circuit may be enabled by an interface controller (174) to assume control of the buffer memory (184,186). By using the buffer memory (184,186) and interface controller (174), whichever of the transponder controller (104) and the external circuitry is transmitting or receiving data may fill or empty the buffer memory (184,186) at either the transponder controller's (104) or the external circuitry's chosen clock rate.

Abstract: A credit-card sized microwave transponder for "wireless key" and surveillance applications uses a subharmonically-pumped quasi-optical mixer. The transponder is activated by a C-band interrogation beam to upconvert and radiate a digitally modulated identification tone at X-band frequencies nonharmonically related to the interrogation signal.

Abstract: This invention provides a tag identification system and method for identifying tags in the range of a reader station where the tags are divided into smaller groups, where the tags are identified one group at a time so as to save power by powering off the tags that are not in the group currently being identified. Each tag puts itself in a group by performing calculations from parameters stored in itself and from parameters received from the reader station. In another variation of this invention, only tags which configure themselves to be activated at a final frequency are identified. The set of tags which configure themselves to be activated at the final frequency changes with each identification round until all tags in the range of the reader have been identified.

Abstract: An identification system comprises an interrogator and a plurality of transponders. The interrogator includes a transmitter which transmits at least two independent interrogation signals to the transponders, and a receiver for receiving response signals from the transponders. The interrogator also includes processor means for identifying the transponders from data in the received response signals. Each transponder comprises receiving means, a code generator, and transmitter means connected to the code generator. On receipt of at least one of the transmitted interrogation signals the transponder transmits a response signal containing data which identifies it. The interrogation signals may be transmitted continuously or intermittently. In a preferred embodiment, the interrogation signals are relatively narrow bandwidth signals at different frequencies.

Abstract: A transponder as well as a data communications system equipped with such a transponder are described, with which identification and/or individual addressing of the simultaneously present transponders is guaranteed in a simple manner even in the case of the simultaneous presence of a plurality of transponders in the field range of the reader.

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: An interrogator-transponder system in which multiple vehicle mounted transponders which may be closely spaced in distance and moving at similar velocities are interrogated by interrogation signals that are identical for all interrogations. Digital coded data blocks consisting of an address code and a message code are transmitted on the interrogation frequency and are interleaved with the interrogation signals. Transponders respond with a coherent identification code and a message data code signal that is displaced in frequency from the interrogation signal by an amount that is identical for each transponder. The transponders decode interrogator data blocks that are associated with an address that is identical to the transponder identification code. The response signal spacings in time are difference for each transponder but are always multiples of the pulse repetition interval of the interrogation signal.

Abstract: The tag circuit system uses resonant circuit technology in conjunction with an insulative substrate and conductive ink or metal conductor to permit the tag to be sewn into the clothing, protecting the circuit elements, yet providing a trace on a portion of the tag which can be clipped from the main portion of the tag to change the operation of the tag. The tag can be configured to resonate at a first frequency outside the frequency of detection, be clipped to resonate at the frequency of detection, and there after subjected to an over current condition to cause the circuit to fail to an open circuit condition to thence be disabled; or it may initially resonate at the detection frequency and then be clipped to an open circuit condition to thence be disabled. The circuit components may be formed of conductive ink or stamped from metal sheet enabling the tag to be inexpensive and to make the circuit components less prominent, particularly where the color of ink used matches the color of the dielectric substrate.

Abstract: A radar sensor/processor for intelligent vehicle highway systems. The radar sensor/processor provides the range, speed, identity of, and selective communications with, vehicles equipped with a transponder in a first cooperative interrogator/transponder mode, and provides information on the range and speed of vehicles without a, or with an inoperative, transponder in a second noncooperative mode. The interrogator includes a first direct digital synthesizer, with an associated first input binary tune register, for producing a sine wave output, a multiplier for multiplying the sine wave output to produce an X-band signal, and a bi-phase single sideband modulator which modulates the X-band signal with data to be transmitted. The interrogator receiver receives a returned transponder reply signal, and includes a balanced mixer for downconverting the reply signal.

Abstract: The invention provides a reader-transponder system that prevents reading of undesired transponder signals. The reader generates a low-frequency signal that is used to supply power to the transponder. The same low-frequency signal also is used to generate a clock signal for the transponder. The reader varies the frequency of the low-frequency power signal according to a code that is unique to the reader. Because the transponder clock signal is derived from the encoded low-frequency power signal, it also varies in accordance with the reader's code. The coded transponder clock signal is contained in the modulation of the RF signal produced by the transponder. When the reader receives and decodes the RF signal, it also extracts the transponder clock signal from the received RF signal and compares variations in the extracted transponder clock signal to the code that was applied to the low-frequency power signal transmitted by the reader.

Abstract: A system and method for communicating between an identification reader 12 and a transponder unit 10 is disclosed herein. A first interrogation signal is transmitted from the reader 12. This first interrogation signal having a first read range. A first response signal is then received at the reader 12 after which a second interrogation signal is transmitted from the reader 12. The second interrogation signal has a second read range which is different than said first read range. The read range can be varied by varying either the amplitude or duration of the power level of the interrogation signal. A second response signal is then received at the reader 12. These consecutive responses are then compared determine a correct response signal which can be displayed.

Abstract: A protocol is used to coordinate the use of a common communication medium by one or more interrogating commander stations and an unknown plurality of responding responder stations. Each commander station and each responder station is equipped to broadcast messages and to check for error in received messages. When more than one station attempts to broadcast simultaneously, an erroneous message is received and communication is interrupted. To establish uninterrupted communication, a commander station broadcasts a command causing each responder station of a potentially large first number of responder stations to each select a random number from a known range and retain it as its arbitration number. After receipt of such a command, each addressed responder station transmits a response message containing its arbitration number. Zero, one, or several responses may occur simultaneously.

Abstract: The present application describes an electronically powered postage stamp or mailing label and including a radio frequency identification (RFID) device and system mounted between the opposing and facing major surfaces thereof. The RFID device and system includes an integrated circuit transceiver chip which is connected to and powered by a thin flat battery cell and is operated with a thin film RF antenna, all of which are mounted in side-by-side relationship on a thin base or support layer. These thin flat components are mounted in an essentially two dimensional planar configuration well suited for incorporation into the planar structure of a postage stamp or a mailing label. In addition, the RFID transceiver chip may be replaced with an electro-optically operated IC chip using, for example, LEDs or laser diodes for the propagation of light signals to an interrogator.

Abstract: There is described an electronic interrogation and identification (I/I) system in which an interrogator/reader (I/R) unit operates remotely using a microwave beam in conjunction with one or more coded articles. The articles are identified by a unique method and search sequence. As the I/R unit interrogates the articles, one or more of them respond to the I/R unit whenever a code word (data value) sent from the I/R unit matches a code word stored in one or more of the memory positions within the articles. After searching through all of the possible code words and word positions the I/R unit will have identified at least one code word stored in each of the word positions of at least one article. Then combinations of the just-identified code words are matched with the respective stored words of the various articles. After being uniquely identified each article is "powered-down" on command from the I/R unit and remains inactive so that one-by-one all remaining articles are also identified.

Abstract: An apparatus including an object 10 associated with a contactless, electronic identifier is disclosed herein. In one example, the object 10 is a trash bin. This object 10 is formed from a non-conductive material. A single-loop antenna 14 is disposed adjacent the object 10. An impedance transformer 18 which is matched to the single-loop antenna 14 is used to generate a desired inductance. A transponder 12 is also disposed near to and associated with the object 10. The transponder 12 is coupled to the antenna 14 through the impedance transformer 18.

Abstract: Apparatus and method for identifying a plurality of transponders (10-16) located within an inquiry field (18) of an interrogation unit (20) are provided. Each transponder (10-16) is assigned an unique identification code, and the interrogation unit (20) dynamically constructs and modifies a bit string used to solicit responses from selected transponder(s) until each transponder (10-16) in the inquiry field (18) is identified. The bit string is transmitted to the transponders, which compares it with the least significant bits of their respective identification codes. A mismatch between the identification code and the bit string results in suppressing the response from the transponder.

Abstract: A transponder interface circuit (172) operates to allow communication between a transponder controller (104) and external circuitry. The interface circuit (172) has a buffer memory (184,186) that allows the transponder controller (104) and the external circuitry each to transmit data at either the transponder's (14) or the external circuitry's clock rate without complicated protocols for direct communication. Each of the transponder controller (104) and the external circuit may be enabled by an interface controller (174) to assume control of the buffer memory (184,186). By using the buffer memory (184,186) and interface controller (174), whichever of the transponder controller (104) and the external circuitry is transmitting or receiving data may fill or empty the buffer memory (184,186) at either the transponder controller's (104) or the external circuitry's chosen clock rate.

Abstract: One or more roadside collection stations (RCS) communicate over a short-range, high speed bidirectional microwave communication link with one or more in-vehicle units (IVU) associated with one or more respectively corresponding vehicles in one or more traffic lanes of a highway. At least two up-link (IVU to RCS) communication sessions and at least one downlink (RCS to IVU) communication session are transacted in real time during the limited duration of an RCS communication footprint as the vehicle travels along its lane past a highway toll plaza. Especially efficient data formatting and processing is utilized so as to permit, during this brief interval, computation of the requisite toll amount and a fully verified and cryptographically secured (preferably anonymous) debiting of a smart card containing electronic money. Preferably an untraceable electronic check is communicated in a cryptographically sealed envelope with opener.

Abstract: The present invention relates to the areas of communication and/or identification of remote devices (active or passive). The invention has application where there is a need to identify or communicate with more than one remote device. The remote device may be embodied as a transmitter arrangement, transducer, transponder or responder. In particular, the present invention calls for each remote device to include a transmitter means in which, at each transmission, a carrier frequency or medium is newly selected.

Abstract: An transponder arrangement (10) for use with tires (20) is described. The arrangement (10) includes an antenna (14) which is mounted about the tire's (20) perimeter. The antenna (14) preferably has a coupling coil (16) at one end. A transponder (12) is preferably located close to the coupling coil (16) and is preferably loosely coupled to the coupling coil (16). The RF-ID efficiency of the arrangement (10) is generally optimized for this type of application by the long but narrow antenna solution and by the simple fact that coupling an antenna (14) to a transponder (12) amplifies the emission of the transponder's signal relative to the noise, thus improving the signal-to-noise ratio of the RF-ID system. The degree of coupling between the antenna (14) and the transponder (12) is not particularly critical. The antenna (14) acts to extend the reading range for the interrogator (24) to be generally, radially symmetric about the tire (20). Other arrangements are disclosed.

Abstract: A system and method which conserves energy in the operation of a transponder or tag (14) by providing that the transponder (14) be enabled or awakened in multiple stages. A threshold detector (62) is provided which measures the power level of received RF energy. If the RF energy received by the detector (62) exceeds a pre-determined level, the transponder (14) then employs a modulation detector (64) to ascertain whether it has been awakened by a valid interrogation signal from an interrogator (12) or whether the RF energy received was merely a spurious burst of RF energy from some other source. If a pre-determined modulation is detected by the modulation detector (64), the transponder (14) is then fully activated to its normal operational state.

Abstract: A Passive Surface Acoustic Wave Identification Tag ("SAW-ID tag") device utilizes pulse compression techniques and a large number of coding possibilities for identifying articles at enhanced ranges. The SAW-ID tag device provides a piezoelectric substrate having bus bars, spaced electrode taps between the bus bars and a built-in antenna, with an input chirped SAW transducer having a dispersive, complementary matched filter response to an input expanded chirp signal from an expanded linear FM chirp waveform actively generated by a nearby chirp transmitter. The input expanded chirp signal is fed into the input chirped SAW transducer through the built-in antenna, to compresses the input expanded chirp signal into a narrow, compressed pulse signal propagating toward the electrodes taps. The spacing of the electrode taps establishes the desired unique time-ordered coding.

Abstract: An improved inductor/antenna (100)improves the selectivity of a recognition system (10) by ensuring that only the transponder (14) closest to the inductor/antenna (100) of an interrogator (12) receives therefrom, and reacts to, an interrogation signal (S1). The improved inductor/antenna (100) also receives the resulting recognition signal (S2) from the transponder (14)for analysis by the interrogator (12). The inductor/antenna (100) includes two or more coils (102,104; 124,126,128,130; 132,134) which may be wound on ferromagnetic cores (108), spaced around a metal mass (46,48) such as a lock cylinder (46) of an ignition switch (24). The shape, number, location and relative winding sense of the coils are selected to shape and locate the energy field (F; 118,122) radiated by the inductor/antenna (100) so that only the transponder (14) in a key (26) which is inserted into or operating the ignition switch (24) responds to the interrogation signal (S1) radiated by the inductor/antenna (100).

Abstract: An improved identification system that employs a novel radio frequency (RF) transponder. The RF transponder comprises a plurality of integrated circuit transponder chips, an RF transmit antenna coupled to an RF output of each of the transponder chips, and a sensor coupled to each of the plurality of transponder chips. A sensor switch is coupled between each of the transponder chips and the RF transmit antenna. The plurality of transponder chips may be individually programmed with different information, or identical information except for one bit. A code reader is coupled to an RF receive antenna for processing data transmitted by the transponder. The transponder is used to transfer information to the code reader relating to an item to which the sensor or transponder is coupled and the condition of the sensor switch. Transmission is accomplished by way of an RF communications link using the RF transmit and receive antennas.

Abstract: A method for interrogating remote transponders having the steps of: sending an RF interrogation pulse from an interrogator (10), receiving by a first and second transponder (12,12a) the RF interrogation pulse, and establishing in a resonant circuit (130) of each of the transponders (12,12a) an oscillation, the oscillation being established by the coupling of signal energy from the RF interrogation pulse into the resonant circuit (130). After the RF interrogation pulse ends, the first transponder (12) senses the termination of the pulse and initiates a first RF response having a selected duration. A second RF response from the second transponder (12a) will also be detected in the first transponder (12) whose response will be affected by this second RF response.

Abstract: A multi-interrogator transponder arrangement is disclosed. The transponder arrangement comprises a first interrogation unit (10) comprising a first wireless datacom transceiver (19) which transmits at least one RF interrogation signal. The arrangement also comprises a second interrogation unit (16) comprising a second wireless datacom transceiver which is in wireless communication with the first wireless datacom transceiver 19. The arrangement still further comprises a responder unit (12) which upon receipt of the RF interrogation signal transmits data stored therein back to the first interrogation unit 10 in the form of a responsive RF communication, the responder unit (12) comprising a responder unit energy accumulator (136) which stores energy contained in the RF interrogation signal. Other devices, systems and methods are also disclosed.

Abstract: A transponder system comprises an interrogation unit for communicating with a plurality of responder units. At least one responder unit receives an interrogation signal from the interrogation unit and returns data as signal information to the interrogation unit in response to the reception of the interrogation signal. The responder unit also includes sensor circuitry sensitive to predetermined physical parameters in the environmental area of the responder unit and, via a data processor, generates data representative of the physical parameter and sends it back to the interrogator as signal information.

Abstract: An object of the invention is to provide a reader which can read transponders having different communication standard protocols with a minimum loss of demodulation speed performance and with the least amount of additional components.

Abstract: A method and system is provided for communicating permanent or semi-permanent information to a transponder (14) from an interrogator (12), preferably operated by a toll agency or other authorized entity. This permanent or semi-permanent information is communicated by means of special instructions valid only during a special mode or maintenance mode which is entered by transmitting a special access code to the transponder (14) from the authorized interrogator (12). The transponder (14) will preferably acknowledge to the authorized interrogator (12) that it is, in fact, operating in the maintenance mode so the interrogator (12) can transmit the special instructions in confidence.

Abstract: A transponder arrangement is described having an interrogator unit (10) which transmits at least one RF programming sequence and at least one RF interrogation pulse. The responder unit (12) includes a responder unit receiver (130) for receiving data transmitted by the RF programming sequence from the interrogator unit (10). The responder unit (12) then upon receipt of the RF interrogation pulse transmits data, which may have been modified by the programming sequence from the interrogator unit (10), back to the interrogator unit (10) in the form of a modulated RF carrier. The responder unit (12) further comprises a responder unit energy accumulator (136) which stores energy contained in the RF interrogation pulse and a responder unit end of burst detector (142) which upon detection of a decreasing power level of the RF interrogation pulse sends a RF threshold signal.

Abstract: Disclosed is a system and method which protects a transponder or tag (14) from being enabled or awakened by spurious RF energy. A modulation detector (64) is provided which detects a modulation signal that is superimposed upon an RF modulation from an interrogator (12). Preferably this superimposed modulation is of a low frequency, below those typically existing as Electro-Magnetic Interference (EMI), such that the transponder (14) is less likely to be erroneously activated by an unintended RF signal. Upon reception of an RF interrogation having the proper modulation superimposed thereupon, the modulation detector (64) is operable to awaken other circuitry within the transponder (14) such that the transponder (14) is then operable to communicate with the interrogator (12).

Abstract: An interrogation unit which has a control circuit and an RF oscillator is described. The interrogation unit further has a transmitter which receives the output of the RF oscillator and transmits at least one RF interrogation pulse of a first frequency for interrogating the responder unit, causing the responder unit to return read data in the form of a RF response. Also in the interrogation unit is a switch for disabling the output of said transmitter and enabling reception of the RF response upon termination of the RF interrogation signal. The interrogation unit still further has a receiver for receiving the RF response upon termination of the RF interrogation pulse and an interrogation unit demodulator for demodulation of the read data from said RF response.

Abstract: A system and method for initiating communication between a controller and a selected one or other subset of multiple transponders in a common RF field in which each transponder has a unique, (or commonly unique) preprogrammed ID number. The controller transmits a series of commands/questions to the transponders and they either respond, or do not respond, to the controller based on their ID number, with the non-responding transponders entering a reset state. The transponders respond to the controller in such a way that, if multiple transponders respond, the controller can recognize that at least one transponder has responded and, for individual responses, the controller is not required to determine how many transponders have responded. Through use of the communications system and method disclosed, a sequence of controller commands and transponder responses single out a selected individual transponder or group of transponders based upon its particular ID number.

Abstract: A hardware and software solution for providing a tamper-proof, batteryless, remote transponder which will only be programmable by an authorized user is disclosed. This goal is achieved through the use of a hardware Cyclic Redundancy Check (CRC) generator which checks during a WRITE function of the data that is received from the Reading/Writing (R/W) unit and also generates several protection bits (Block Check Character; BCC) which are sent back during the response function (READ). Before the CRC generator checks the data during a WRITE function, however, it must be set to a predetermined start value called a Segment Code, and the Segment Code of the R/W unit must be the same as the Segment Code of the transponder in order for a Write (or a READ) to be performed. Additionally, programming of the Selective Address must be done within a predetermined time window (has a predetermined Time Code).

Abstract: A hand-portable position locating radio has a geolocation (e.g. GPS) receiver providing local position and timing information from geolocation means (e.g. GPS or IRIDIUM satellites) and a local transceiver for sending local position and other information to a communication system (e.g., an IRIDIUM or MILSAT satellite). A data processor coupled to the local transceiver and receiver controls operation of the device, including storing local position information and separating signals broadcast by the communication system into those intended or not intended for the device. The radio prepares an emergency access message which it sends to the satellite communication system in a manner to insure rapid detection of the emergency signal and allocation of a clear channel and time slot for further communication.

Abstract: A responder unit (12) located in spaced relation with respect to an interrogator unit (10) is described. The responder unit (12) has a responder unit receiver (130) for receiving at least one RF interrogation pulse, a responder unit memory (168) containing a potentially unique responder unit group address, a responder unit controller (202) operably connected to the memory (168) for comparing the potentially unique responder unit group address to the Group Address, and a responder unit transmitter (130) for transmitting a RF response when the potentially unique responder unit group address matches the Group Address.

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.