Abstract: A system and method for determining the position of a radio frequency identification (RFID) transponder with respect to a sensor. In one embodiment, the system comprises a plurality of stationary sensors located in an array within certain physical areas. Each sensor comprises a plurality of antenna coils arranged in unique physical orientations and capable of transmitting radio frequency signals of differing phase. The RFID transponder includes an antenna which receives the plurality of signals generated by the antenna coils, and compares the phase of at least two of the signals to determine the relative position of the transponder. In a second aspect of the invention, the aforementioned antenna coils emit two direction finding mode (DFM) signals in succession; the first signal with all antenna coils turned on, the second with one of the coils turned off.

Abstract: A reader/writer (RW) requires identification of anti-collision techniques used by IC cards (A, B, C, and D). The IC cards implement answers to the anti-collision technique identification requirement by the reader/writer at different timings respectively for respective IC cards among the IC cards which use different anti-collision techniques respectively. The reader/writer requires identifications of types of the IC cards in dependence upon the anti-collision techniques in response to the answers by the IC cards. The IC cards return identification data thereof in response to the card type identification requirements by the reader/writer for respective IC cards among the IC cards which use different anti-collision techniques respectively. The reader/writer identifies the types of the IC cards in response to the identification data of the respective IC cards.

Abstract: Described herein is a circularly polarizing radar transponder. The circularly polarizing radar transponder comprises a helical type circularly polarizing antenna unit for receiving all of a circularly polarized wave, a vertically polarized wave and a horizontally polarized wave therein, a receiver unit connected to the helical type circularly polarizing antenna unit, a transmitter unit for generating a plurality of pulses with a radio wave received by the receiver unit as a trigger, and a battery unit for supplying power to these receiver and transmitter units.

Abstract: A wireless identification device including a housing; circuitry in the housing configured to provide a signal to identify the device in response to an interrogation signal; and a selectively actuated switch supported by the housing and permitting operation of the circuitry only while the switch is actuated. A method of manufacturing a wireless identification device, the method including configuring circuitry to provide, a signal to identify the device in response to an interrogation signal; coupling the circuitry to a selectively actuated switch, such that the circuitry provides the signal only while the switch is actuated; and encasing the circuitry in a housing such that the switch is actuable from outside the housing by touching a portion of the housing.

Abstract: A method for simultaneously reading a serial number and/or other information from multiple colliding RF signals from RF identification tags requires minimal additional logic in the tag's processor and provides for a powerful and rapid sorting and identification scheme. This technique employs a primary communication channel and multiple secondary channels. A locator or reader unit interrogates the tags, which respond with an RF signal. Upon receiving multiple signals, the locator or reader unit commands the RFID tags and requires them to transmit another response, which is transmitted in one of the secondary channels based on a portion of their unique serial identification number, thereby forcing the tags to sort in the secondary channels. These secondary channels are assigned using a portion of the unique serial identification numbers for the tags. The reader then detects an acknowledgment in the occupied secondary channels and commands a tag in a particular channel to move to the primary channel.

Abstract: A method and a system for monitoring a plurality of movable objects, wherein each of the objects is equipped with a transponder with which a stationary node is arranged to communicate. Each transponder is caused to reply to a unique signal from the node and each transponder that sends a response signal gives to the response signal a transponder identification addition. A node is caused to detect the speed and direction at which each transponder moves towards and away from the node. Movement of the transponder relative to the node is evaluated by node associated means on the basis of the speed and direction of the transponder. A register over those transponders with which the node shall communicate is set-up for each node. A plurality of separate nodes are provided and each node is provided with such a register. The nodes are arranged to communicate with one another, so as to enable a node to record in its monitoring register a transponder from another node.

Abstract: An object identification system includes a monitor and a plurality of transceivers that communicate over a common medium. The monitor includes a first transmitter, a first receiver, and a processor. Each transceiver includes a resonant circuit, a transmitter, a receiver, and an antenna coupled to the resonant circuit. The processor performs a method for performing transceiver communication that includes the steps of: (a) transmitting from the first transmitter a first frequency for a first duration; (b) after lapse of the first duration, receiving via the first receiver a response signal from at least one of the resonant circuits; (c) determining a second frequency from the received response signal; and (d) performing transceiver communication using the second frequency.

Abstract: Interrogators, wireless communication systems, methods of operating an interrogator, methods of monitoring movement of a radio frequency identification device, methods of monitoring movement of a remote communication device and movement monitoring methods are provided. According to one aspect, an interrogator includes communication circuitry configured to output a forward wireless signal to a radio frequency identification device and to receive a return wireless signal from the radio frequency identification device; and a processor coupled with the communication circuitry and configured to process the return wireless signal to monitor movement of the radio frequency identification device.

Abstract: An electromagnetic transponder is provided that includes an oscillating circuit, an electronic circuit, a rectifying circuit, and a capacitive modulation circuit. The oscillating circuit includes an inductive clement and the electronic circuit includes a transmission circuit for transmitting digitally-coded information. The rectifying circuit is coupled to the oscillating circuit to provide a DC supply voltage to the electronic circuit, and the capacitive modulation circuit is coupled to both end terminals of the inductive element and to the reference potential of the electronic circuit. In a preferred embodiment, the capacitive modulation circuit includes two capacitors, with capacitor being coupled between one end terminal of the inductive clement and the reference potential and the other capacitor being coupled between the other end terminal of the inductive element and the reference potential.

Abstract: System for tracking mobile tags. Cell controllers with multiple antenna modules generate a carrier signal which is received by the tags. Tags shift the frequency of the carrier signal, modulate an identification code onto it, and transmit the resulting tag signal at randomized intervals. The antennas receive and process the response, and determine the presence of the tags by proximity and triangulation. The recursive-least squares (RLS) technique is used in filtering received signals. Distance of a tag from an antenna is calculated by measuring the round trip signal time. The cell controllers send data from the antenna to a host computer. The host computer collects the data and resolves them into positional estimates. Data are archived in a data warehouse, such as an SQL Server. Also disclosed is an article tracking system that supports both active and passive tags with a cell controller able to read both passive and active tag signals.

Abstract: A method and a system for monitoring a plurality of movable objects, wherein each of the objects is equipped with a transponder with which a stationary node is arranged to communicate. Each transponder is caused to reply to a unique signal from the node and each transponder that sends a response signal gives to the response signal a transponder identification addition. A node is caused to detect the speed and direction at which each transponder moves towards and away from the node. Movement of the transponder relative to the node is evaluated by node associated means on the basis of the speed and direction of the transponder. A register over those transponders with which the node shall communicate is setup for each node. A plurality of separate nodes are provided and each node is provided with such a register. The nodes are arranged to communicate with one another, so as to enable a node to record in its monitoring register a transponder from another node.

Abstract: A communication device (6) includes detection means (28) adapted to detect a value (V), which value (V) represents a maximum amplitude value of a data carrier signal (DS) produced by a data carrier (10, 12, 14, 16, 18, 20) as it moves through a communication range (KB) of the communication device (6) along a predetermined path and received with the aid of receiving means (23) of the communication device (6), the detection means (28) being adapted to supply a detection signal (RS) upon detection of the value (V) representing the maximum amplitude value.

Abstract: A method of communicating to a RF tag having a low power mode and a scan mode with a radar and an interrogator. The method comprises the steps of alternating the RF tag between the low power mode and the scan mode and then transmitting a wake-up call to the RF tag with the radar. Next, the wake-up call is received from the radar by the RF tag when the RF tag is in the scan mode. Once the wake-up call has been received, the radar will transmit a downlink message to the RF tag. Upon receipt of the downlink message, the RF tag will send an uplinked message to the radar. After the uplink message has been sent to the radar, the RF tag will return to the low power mode. By alternating the RF tag between the low power mode and the scan mode, the power consumption of the RF tag is greatly reduced thereby increasing the battery life thereof.

Abstract: This invention allows a toll authority to monitor transaction numbers which are sent from a transponder (14) to an interrogator (12). By incrementing the transaction counter stored in the transponder with successful transactions the toll authority can ascertain whether accounting of a transaction has been missed (i.e., a transaction number missing from the sequence), or double-counted (i.e., two transactions with the same transaction number).

Abstract: A tag which uses radio frequency waves transmitted from a scanning device in order to identify an item to which the tag is attached or with which the tag is associated. The tag includes a first insulating layer having a top surface and a bottom surface, and resonant circuits formed on the first insulating layer. Each of the resonant circuits are formed on one of the top surface and the bottom surface of the first insulating layer and have a resonant frequency associated therewith. Each of the resonant circuits include capacitance and inductance elements. The capacitance and inductance elements include an inwardly spiralled coil connected to an outwardly spiralled coil. The tag is associated with a binary number established by a pattern of ones and zeros depending on each circuits' resonance or nonresonance, respectively.

Abstract: A transponder reading device and a control system for controlling the handling and/or processing of transponder-bearing objects by such transponder reading devices. The transponder reading device is equipped with its own microcontroller, and with its own control unit. The microcontroller is, as a component (node) of a control unit, able to communicate with other devices of the same design to exchange information. Consequently, several such devices can be operated simultaneously in a confined space without interfering with each other.

Abstract: A radio frequency identification transponder (RFID tag) in accordance with the principles of the present invention includes a tag antenna and RFID circuitry having respective input impedances Za and ZL. In accordance with the principles of the invention, the read distance of the RFID tag is maximized by connecting an inductor in series between the antenna and the RFID tag circuitry. The inductor having an impedance ZL that maximizes the expression [(Ra)(Ga)]½|(ZL|/|Za+Zind+ZL|, where | | indicates the absolute value of the enclosed expression.

Abstract: A passive garage door opener system includes a sensor for determining the position of the vehicle relative to the receiver. When the vehicle is within a predetermined area near the receiver, the transmitter sends the signal to open the garage door. Other conditions of the vehicle, such as speed and heading, may also be monitored to determine when and whether to send the signal.

Abstract: A transponder communication device interrogates an operational test transponder that is permanently within a receiving range of the transponder communication device. In response thereto, the operational test transponder sends operational test information to the transponder communication device. The transponder communication device checks whether received operational test information is valid, and generates an error signal if the received operational test information is invalid.

Abstract: A system and method for determining a location. The system employs encoded information devices dispersed through the environment, each having a non-unique code associated therewith. The codes from the encoded information devices are acquired as a reading device passes nearby, and stored. The codes from a proximate set of information devices are correlated with a map or mapping relation to determine one or more consistent positions within the environment. The information devices are preferably passive acoustic wave transponders, and the mapping relation may be a pseudorandom sequence or a defined map.

Abstract: A method and apparatus for attaching a RF/ID transponder to an object is described. The transponder is integrated within an attaching device to protect the transponder from damage, hazardous environments and tampering. Further, by integrating the transponder within the attaching device, the device can be countersunk to further protect the transponder. Further still, manufacturing the device from a non-ferrous material prevents degradation of the transponder reading range.

Abstract: For reading the data stored in a transponder by means of an interrogation device, the interrogation device at first receives the background noise for the purpose of detecting interference frequencies present in this background noise. On the basis of the interference frequencies acquired, coefficients for an adaptive filter are computed by means of which this filter may be tuned in such a way as to suppress the interference frequencies. The response signal from the transponder with the superimposed background noise is received by the interrogation device and routed through the adaptive filter which acts to suppress the interference frequencies. The signal available at the output of the filter can then be demodulated for the purpose of reading the data stored.

Abstract: In accordance with the present invention, a general antenna system is disclosed suitable for applications in which an RFID Tag passes by an Interrogator. We then disclose a specific antenna design that uses a single planar antenna for transmit and a multi-element planar antenna array for receive. The multi-element planar antenna array is spaced such that each of the planar elements is four inches apart, center-to-center, thus defining a narrow 30° receive beamwidth in the horizontal plane. The vertical receive bandwidth is much greater than 30°, facilitating the Interrogator receiving signals at a variety of elevations. Furthermore, a multi-way microstrip combiner is used to sum the signals received from each of the planar antennas. To block interference from the transmit antenna and to improve receive sensitivity, this multi-way microstrip combiner is shielded using, in one embodiment, copper tape along its edges. In a specific embodiment, a four element receive antenna design is disclosed.

Abstract: A method of forming a radio frequency communication apparatus includes providing a substrate provided with an outermost surface. An RFID is adhered at least partially within the substrate, and the RFID includes an antenna and an integrated circuit. The RFID and substrate together form a radio frequency communication apparatus. A method of forming a radio frequency communication apparatus includes providing a substrate with a frontside surface. An opening is formed through the frontside surface and into the substrate. An RFID is inserted within the opening and adhered to the substrate within the opening. The RFID includes an antenna and an integrated circuit to form a radio frequency communication apparatus.

Abstract: An impedance matching circuit in accordance with the principles of the present invention employs series-connected transmission lines to match a high reflection coefficient source impedance with a load impedance. The matching circuit is formed on a dielectric substrate material and accommodates the relatively limited capabilities of photo-lithographic circuit production. The new impedance matching circuit may be constructed of three series-connected transmission line sections. A first section, the section that is to be connected to the source, transforms the high source impedance into a relatively low valued impedance that is substantially resistive. The reflection coefficient of the first section is substantially equal to the reflection coefficient of the source. A second may be implemented as a quarter-wave transformer that transforms the low impedance developed by the first section into an intermediate impedance value.

Abstract: System for tracking mobile tags. Cell controllers with multiple antenna modules generate a carrier signal which is received by the tags. Tags shift the frequency of the carrier signal, modulate an identification code onto it, and transmit the resulting tag signal at randomized intervals. The antennas receive and process the response, and determine the presence of the tags by proximity and triangulation. Distance of a tag from an antenna is calculated by measuring the round trip signal time. The cell controllers send data from the antenna to a host computer. The host computer collects the data and resolves them into positional estimates. Data are archived in a data warehouse, such as an SQL Server.

Abstract: In an access control system (8)--which comprises a transponder communication device (9) and at least two transmission coils (11, 12) connected to the transponder communication device (9), for receiving transponder signals, of which a first transmission coil (11) is associated with a first door (2), and which comprises a first activation device (18 associated with the first transmission coil (11) and the first door (12), and which comprises a first door opener (23) for the first door (2) and a logic device (45) for activating the first door opener (23)--the two transmission coils (11, 12) have arbitrarily large receiving ranges and the first transmission coil (11) and at least one further transmission coil (12) are followed by amplitude detector (34, 36) by which the amplitudes of the transponder signals supplied by the two transmission coils (11, 12) can be detected and the logic device is arranged after the amplitude detector (34, 36) and adapted to detect a condition in which the amplitude of the transponde

Abstract: A radio frequency identification device comprises an integrated circuit including a receiver, a transmitter, and a microprocessor. The receiver and transmitter together define an active transponder. The integrated circuit is preferably a monolithic single die integrated circuit including the receiver, the transmitter, and the microprocessor. Because the device includes an active transponder, instead of a transponder which relies on magnetic coupling for power, the device has a much greater range.

Abstract: A holder is provided for the reception and selective shielding of an electronic vehicle identifying device conventionally used in conjunction with automatic toll collection. The holder includes a shielding portion which is manually actuated by the vehicle operator when it is desired to permit communication between the signal of the vehicle identifying transponder and an externally located interrogator which ascertains the presence of the vehicle.

Abstract: A document or object includes resonant tags, such as thin dipoles, and a machine-readable symbol, such as an area symbol, secured thereto. A reader reads the symbol and determines response characteristics encoded therein for the dipoles. The reader then can interrogate the dipoles and, together with the response characteristics and determined orientation (derived from the symbol), accurately determine resonant response characteristics received from the dipoles. Alternatively, a printer may interrogate the document to determine the response characteristics of the dipoles in the document, and then print the corresponding symbol.

Abstract: A contactless identification and communication system and method of operating a contactless identification communication system comprising a reader and one or more transponders, wherein the or each transponder is operable to be in RF communication with the reader, which method comprises the steps of: operating the transponder at a first clock rate when the transponder is not transmitting to the reader; and operating the transponder at a second clock rate during transmission of data from the transponder to the reader, the second clock rate being higher than the first clock rate.

Abstract: The present invention relates to a universal anti-theft device for securing articles against theft, which has at least one electromagnetic resonant oscillating circuit (2) that, in the interrogation field of an article monitoring system, is excited to transmit a characteristic signal which subsequently trips an alarm and at least one further electromagnetic resonant oscillating circuit which contains specific, encoded information about the article. The present invention also relates to a method for producing the universal anti-theft device for securing articles against theft.

Abstract: A golf distance indicator system provides measurement and display of the distance between a golfer and the pin on the green he is approaching. The system comprises a portable unit carried by the golfer and an target unit located on the pin. With the portable unit, the golfer selects the hole he is playing then activates the system. The portable unit sends a wireless coded message to an intended target unit. When a target unit receives a message, it analyzes the message to see if it should respond. If the target unit determines that it should respond, it sends a coded responding message to the portable unit. When the portable unit receives a responding message, it analyzes the responding message to see if the responding message originates from the intended target unit. If it does, the portable unit calculates a distance based on the elapsed time for the communications and the speed of the communications. The results are displayed on the portable unit.

Abstract: A radio frequency identification system employing a thin, flexible electronic radio frequency identification (RFID) tag having an overall thickness not exceeding approximately 280 microns and the process for its manufacture is disclosed. The RFID tag includes an insulating, flexible substrate having an aperture formed therein for receiving an RFID circuit chip. An antenna forming an integral part of the substrate is electrically connected to circuit chip. A cured adhesive having a portion substantially parallel with the substrate encapsulates the circuit chip so that the chip is operably retained within the substrate aperture.

Abstract: The RF tag system of the present invention minimizes the effect of the RF tag on the overall radar cross section (RCS) of the object with which it is associated, tailors the signal reflected from the tag to match the actual RCS of the object with which it is associated, utilizes an RF tag design that reduces degenerative RF coupling at the tag, and is designed to exploit the operational features of conventional pulse Doppler radars. In accordance with one embodiment of the present invention, a radio frequency tag system is provided including an interrogator and a tag. The tag is secured to an object. The interrogator is configured to generate a transmitted electromagnetic interrogation signal at a predetermined interrogation frequency. The tag comprises an antenna array including a plurality of receiver antennas and a plurality of transmitter antennas.

Abstract: A fast data transfer collection system using message authentication and contactless RF proximity card technology in non-contact storage and retrieval applications. The system is generally comprised of Host computers (application computer systems), Target radio frequency (RF) terminals, and a plurality of portable Tags ("smart" or "proximity" cards). A Host provides specific application functionality to a Tag holder, with a high degree of protection from fraudulent use. A Target provides control of the RF antenna and resolves collisions between multiple Tags in the RF field. A Tag provides reliable, high speed, and well authenticated secure exchanges of data/information with the Host resulting from the use of a custom ASIC design incorporating unique analog and digital circuits, nonvolatile memory, and state logic. Each Tag engages in a transaction with the Target in which a sequence of message exchanges allow data to be read(written) from(to) the Tag.

Abstract: A transponder communication device has an interrogation signal generator for generating an interrogation signal, a transmitter for transmitting the interrogation signal to a number of transponders, and a receiver for receiving answers signal from transponders. A transponder has an interrogation signal detector, an answer signal generator, and a state setting controller for setting a state of the transponder. The transponder communication device selects a single transponder from the number of transponders. First, the transponder communication device transmits an initial interrogation signal is transmitted to all transponders when the transponders are in an active state. In dependence of answer signals received from the transponders, the transponder communication device transmits a standby setting signal to at least one transponder at a time to instruct the transponders to adopt a standby state. In the standby state the transponders wait until a single other transponders has been selected.

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: In a first embodiment, a voltage controlled oscillator (VCO) is driven by a generator that provides a cyclic voltage having a sawtooth waveform. The VCO cyclicly provides a signal at a frequency that varies over a range that includes a frequency of a transmitted signal that causes a vehicular traffic signal light control system, of a type that has an inductive loop buried in a roadway, to provide a desired illumination of traffic signal lights of the system. The VCO is connected to a power amplifier that has its output connected to an antenna. In a second embodiment, a signal processor provides a train of pulses at a frequency of radiation from the inductive loop. The number of the pulses of the pulse train that are provided during a timing interval is stored by a counter. A digital to analog converter is connected to the output of the counter. After the timing interval, a signal is transmitted substantially at the frequency of radiation in response to the output of a VCO that is connected to the converter.

Abstract: A distancing system comprising radio frequency transceivers and data processing circuits. The radio frequency transceivers allow data transmission via a high frequency radio signal. The transmission and receipt of these radio signals can be timed to estimate distance. But the data processing circuits operate at local clock frequencies, and one cannot be sure at what point a give radio frequency signal was received to a resolution greater than one-half cycle of the local clock signal. The data processing circuits periodically "skip" to resynchronize with incoming data streams. These skips occur at intervals corresponding to the frequency difference between the local clock frequencies. This frequency difference can be used to pinpoint fairly precisely when a given radio frequency signal was received in a previous half-cycle of the local clock.

Abstract: An antitheft system for a motor vehicle includes a transponder having a charging capacitor which is wirelessly charged by energy signals from a transceiver. The level of the energy being transmitted depends on the quality of an inductive transmission between the transponder and the transceiver. Too little energy is transmitted if the exciting frequency of a transceiver oscillating circuit does not correspond to its resonant frequency due to component tolerances. In order to ensure that the charging capacitor is always quickly and properly charged, the exciting frequency is varied within a predetermined frequency range during a charging phase so that it passes in the vicinity of the resonant frequency at least once.

Abstract: A method of controlling access to a movable container, the method comprising controllably locking the container using an electronically actuated locking mechanism; storing in a memory a desired geographical location; determining the geographical location of the container; and enabling the locking mechanism to unlock the container if the determined geographical location matches the desired geographical location.

Abstract: A non-linear junction detector designed for counter surveillance measures achieves superior performance by using a single circularly polarized antenna to transmit a signal and to receive harmonics of the transmitted signal that are re-radiated by a non-linear junction such as would be found in a eavesdropping device containing a semiconductor. The antenna is mounted on a telescoping antenna extension assembly. A single electrically conductive cable is contained inside the antenna and connects the antenna to the transceiver case which houses the non-linear junction detector electronics. A cable winder is built into the antenna and is employed to provide automatic dispensing and retraction of the cable when the antenna extension assembly is extended or retracted. A display is built into the antenna head assembly to provide signal strength indications and operational information concerning the functioning of the non-linear junction detector to the user of the device.

Abstract: A transponder 20 for an electronic identification system transponder is characterized in that it presents a high input impedance (>400.OMEGA.) at an input thereof which is directly connected to an antenna 22 with a matched high input impedance. The transponder is aimed at improving the voltage recovered on capacitor C.sub.2 from an interrogation signal and thus the operational range of the system. The modulator 30 of the transponder is arranged to backscatter modulate the interrogation signal at a modulation depth of less than 80%, preferably in the order of 30%. This also results in an improvement of the operational range of the system.

Abstract: A new VIN Reading and Transmitting System for providing a device for automatically detecting a vehicle identification number and transmitting the number to a dispatch station for immediate identification of the vehicle and owner. The inventive device includes a vehicle unit containing the vehicle identification number, a portable unit which enables the vehicle unit to transmit the number which is detected by the portable unit, a digital repeater which receives a signal from the portable unit for transmitting to a receiver at the dispatch office where the number can be utilized to disclose the vehicle and the owner which can be transmitted to the police officer immediately.

Abstract: A radio communications system is that can determine the location of an RFID Tag. The radio communication system includes at least one Interrogator for generating and transmitting a modulated radio signal to one or more Tags. The Interrogator is at a known location, and is in motion with respect to the Tag at a known velocity. One or more Tags of the system receive and demodulate the modulated radio signal, which contains a first information signal which specifies which Tag or Tags should respond using Modulated Backscattering. The Tag generates a subcarrier signal, and backscatter modulates the reflection of the radio signal using the subcarrier signal, thereby forming a reflected signal. The Interrogator receives and demodulates the reflected signal. The Interrogator then determines the Tag's relative direction from the location and velocity of the Interrogator, and from the Doppler shift of the subcarrier signal. More than one of such measurements allow the location of the Tag to be determined.

Abstract: A radio-communication vehicle identification apparatus includes first and second radio communication units, a directional finding unit, a vehicle classification unit, and a vehicle identification unit. The first radio communication unit is mounted on a vehicle. The second radio communication unit is placed at a gate through which the vehicle passes to perform radio communication with the first radio communication unit. The directional finding unit measures an arrival angle of a radio signal transmitted from the first radio communication unit with respect to a reference direction. The vehicle classification unit detects a length of the vehicle on the basis of image data obtained by photographing the vehicle and classifies the vehicle on the basis of a detection result.

Abstract: This radiofrequency interface device (1) for a transponder, comprises a coil (2) forming the antenna of the transponder and a voltage converting circuit (4) connected, on the one hand to the terminals (5, 6) of said coil (2) and, on the other hand, to continuous voltage supply terminals (V.sub.dd, V.sub.ss) of an integrated logic circuit (7) of the transponder, and is characterised in that the terminals (5, 6) of the coil (2) are connected to floating potentials with respect to the substrate of the transponder, so that none of the terminals (5, 6) of the coil (2) passes below the potential (V.sub.ss) of the substrate.

Abstract: A transponder antenna is carried by a substrate and is sandwiched between the substrate and a cover sheet. A rectangular opening extends through the cover sheet and receives a signal processing chip adhesively carried in a recess below a cap which covers the opening. The chip is spaced with respect to the antenna so as to facilitate direct or inductive coupling between the chip and antenna. The cap has a protective portion which extends through the cover opening substantially all the way to the substrate so as to prevent accidental contact between the chip, on one hand, and the substrate and/or antenna on tee other.

Abstract: In a non-stop automatic toll collection system for exchanging information by radio between a vehicle-mounted device mounted on a vehicle and a toll station, the toll station side comprises two receivers having different directional properties. The gain of one receiver is high when the vehicle is inside a toll collection area in which a toll charge is collected, and the gain of the other receiver is high when the vehicle is outside this toll collection area. It can therefore be determined whether the source emanating the received radio waves is inside or outside the toll collection area by comparing the intensity of the signal received by these two receivers.