Abstract: Devices having either wireless data communication capability or RFID tags can be located using dual function fixed devices which are distributed throughout a facility. The devices will identify those units with which they are communicating using a wireless radio data communications protocol and also identify items within the local area using RFID tags on the units.

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: Disclosed herein is a critical band encoding technology (CBET) system having at least one portable people meter (PPM) and a home base station and/or household hub, the CBET system containing a radio frequency (RF) proximity detection and identification system, comprising at least one RF transmitter for receiving a control signal, modulating an RF signal to a present modulation frequency upon receipt of the control signal, and wireless transmitting the modulated signal; and an RF receiver for receiving the wirelessly transmitted modulated signal, determining the modulation frequency, and transmitting the modulation frequency to a remote location, wherein the transmission power of the RF transmitter is preset to transmit the modulated data within a predetermined range.

Abstract: A method and an identification system us for communicating between a reader and a plurality of transponders. The reader has a transmitter for transmitting a signal and each transponder includes a receiver for receiving the reader signal and a transmitter for generating a transponder signal. When the reader recognises a transponder signal from one of the transponders it immediately issues a mute instruction, muting all other active transponders and passing control to the said transponder, without the need for a specifically timed acknowledgement to the said controlling transponder. The reader may issue a single disable/wakeup instruction which disables the controlling transponder returning control to the reader and reactivated all muted (but not disabled) transponders.

Abstract: A smart vehicle registration plate for a vehicle have a computing unit configured to process vehicle related information, and a display, the display having one or more information display regions, for displaying the vehicle related information. The information display regions may be updateable by the computing unit as a function of changes to the vehicle related information.

Abstract: A method for identifying and determining the position of rolling stock within a railyard using a system that includes an AEI reader, a plurality of elevated electronic imaging devices and a tracking computer. The rolling stock includes a plurality of railcars and a plurality of locomotives. The method includes recording an identification pattern for each piece of rolling stock as each piece enters the railyard, compiling tracking data of the rolling stock as the rolling stock moves within the railyard using the respective identification patterns, and mapping the position of each piece of rolling stock as the rolling stock moves within the railyard.

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

Abstract: The present invention provides an apparatus, method, and system for determining a time of arrival (TOA) and time differences of arrival (TDOA) of a transmitted signal {S} receivable at different locations of known spatial coordinates. The system comprises a first transmitter 10 with a respective antenna feed point positioned at an a priori unknown location P and emitting a first signal {S}. The system includes furthermore a set of transceivers or transponder units 20, 30 comprising first receivers 22, 32 for receiving first signals {S} by means of respective antennas with feed points located at known locations Ln. Such system also comprises second transmitters 26, 36 emitting respective derived second signals {{tilde over (S)}n} after known and scheduled respective time intervals &dgr;n as measurable between the feed points of said respective first receiving antennas located at known locations Ln and respective second transmitting antenna located at locations L′n.

Abstract: A system which allows multiple senders to asynchronously transmit identification codes via a common communication channel (e.g., RF) to enable a central monitor to identify the presence (or absence) of each sender within the monitor's detection zone. Each sender is configured to repeatedly transmit a uniquely encoded identification frame. A frame, in accordance with the invention, is comprised of pulses spaced to minimize pulse collisions and configured to tolerate occasional collisions without impairing the monitor's ability to separately identify each transmitting sender. Each sender is configured to repeatedly transmit a unique identification frame characterized by a pulse pattern comprised of active intervals spaced by inactive (or “quiet”) intervals. The inactive intervals have variable length durations which are preferably pseudorandomly selected so that each sender defines a unique sequence of inactive interval durations.

Abstract: Methods and systems for determining the direction to a transponder are disclosed. The methods and systems include transmitting a first signal to an area where communications with a transponder is desired; producing a second signal desired from the first signal; receiving the second signal via a first and second antenna forming a difference signal from the second signal received via the first and second antennas; forming a third signal by adding the second signal received via the first antenna and the second signal received via the third antenna; delaying the difference signal; and comparing a fist polarity of the delayed difference signal with a second polarity of the third signal.

Abstract: A communication device includes detection a detector (28) adapted to detect a value (V) which represents a maximum amplitude value of a data carrier signal (DS) produced by a data carrier as it moves through a communication range (KB) of the communication device along a predetermined path and received with the aid of a receiver (23) of the communication device. The detector is adapted to supply a detection signal (RS) upon detection of the value (V) representing the maximum amplitude value.

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: An enhanced backscatter RF-ID tag reader system and multiprotocol RF tag reader system is provided. In a multiprotocol mode, the system emits a non-stationary interrogation signal, and decodes a phase modulated backscatter signal by detecting a stronger phase component from quadrature phase representations or determining phase transition edges in a phase of a received signal. The RF tag reader system predicts or follows the phase of the backscatter signal, thereby avoiding interference from nulls in the received signal waveform due to the non-stationary in terrogation signal, relative movement or environmental effects. An acoustic RF-ID tag detection system detects the reradiated signal corresponding to respective transformation of a signal in the tag. Detection of either type of RF-ID tags therefore is possible, and the absence of any tag or absence of any valid tag also determined.

Abstract: A method for identifying a person authorized to enter into a secured transaction, including implementing a security system to receive a coded signal that purports to identify as an authorized person the wearer of a device generating the coded signal through a transmission link constituting the body of the wearer, upon physical contact between an input terminal of the security system and the body of the wearer. After purported identification of the wearer as an authorized person for the transaction, data stored in a memory of the device is delivered to assist in processing the transaction by access through the security system. Data stemming from the transaction is retrieved for updating data stored in the memory, usable in a subsequent transaction by the wearer.

Abstract: This invention is a radar/tag system where pulses from a radar cause a tag (or transponder) to respond to the radar. The radar, along with its conventional pulse transmissions, sends a reference signal to the tag. The tag recovers the reference signal and uses it to shift the center frequency of the received radar pulse to a different frequency. This shift causes the frequencies of the tag response pulses to be disjoint from those of the transmit pulse. In this way, radar clutter can be eliminated from the tag responses. The radar predicts, to within a small Doppler offset, the center frequency of tag response pulses. The radar can create synthetic-aperture-radar-like images and moving-target-indicator-radar-like maps containing the signature of the tag against a background of thermal noise and greatly attenuated radar clutter. The radar can geolocate the tag precisely and accurately (to within better than one meter of error).

Abstract: A method of processing reply signals received in response to an interrogation by a secondary surveillance radar system. The method includes the steps of receiving a reply signal from each of a plurality of targets, and enabling each of a plurality of target mode blocks having a predefined mode to select from the reply signals. The method further includes the step of correlating the selected reply signal to the target mode block that selected same.

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

Abstract: A vehicle wireless transmitter system includes a collision avoidance sensor in a wireless transmitter. The wireless transmitter generates a wireless signal, such as a garage door opener signal, based upon information from the collision avoidance sensor. The wireless transmitter generates a garage door opener signal when the collision avoidance sensor determines that the vehicle is within a predetermined distance of the garage. The wireless transmitter generates a garage door opener signal when the collision avoidance sensor determines that the vehicle is in the garage, the engine is no longer running and no motion is detected around the vehicle for a predetermined period of time.

Abstract: A locator according to various aspects of the present invention includes a receiver and a processor. The receiver receives several signals, each signal having respective indicia of identification device presence within a respective communication pattern. The processor performs a method for determining whether a first identification device is located within a zone. The method includes the following steps performed in any order. A first step of determining, in response to receiver signals, a respective reliability of communication between the receiver and a plurality of identification devices. The plurality includes the first identification device and at least one second identification device. A first and a second communication pattern each respectively has a periphery such that communication with a provided identification device when located beyond the periphery is less reliable than communication with the provided identification device when located within the periphery.

Abstract: A collision resolution system and method for enhanced non-contact automated data collection. The data collection system generally includes a plurality of portable fare tags or token (“smart”) cards and a stationary target terminal. Each tag exchanges a series of messages with the target terminal to establish a communication link for the transfer of financial or other data. Concurrently, each tag and the target terminal process the messages to provide collision resolution, thereby ensuring that only one tag, at any instance, establishes the communication link with the target.

Abstract: Methods and systems for determining the direction to a transponder are disclosed. The methods and systems include transmitting a first signal to an area where communications with a transponder is desired; producing a second signal desired from the first signal; receiving the second signal via a first and second antenna forming a difference signal from the second signal received via the first and second antennas; forming a third signal by adding the second signal received via the first antenna and the second signal received via the third antenna; delaying the difference signal; and comparing a fist polarity of the delayed difference signal with a second polarity of the third signal.

Abstract: An RF transponder identification system with an interrogator operable to transmit a plurality of marker signals and a plurality of transponder. Each transponder has a random number associated therewith, a counter counting the number of marker signals received from the interrogator and transmission means to transmit an identification code when the number of marker signals received by the transponder equals the random number associated with the transponder.

Abstract: An enhanced backscatter RF-ID tag reader system and multiprotocol RF tag reader system is provided. In a multiprotocol mode, the system emits a non-stationary interrogation signal, and decodes a phase modulated backscatter signal by detecting a stronger phase component from quadrature phase representations or determining phase transition edges in a phase of a received signal. The RF tag reader system predicts or follows the phase of the backscatter signal, thereby avoiding interference from nulls in the received signal waveform due to the non-stationary interrogation signal, relative movement or environmental effects. An acoustic RF-ID tag detection system detects the reradiated signal corresponding to respective transformation of a signal in the tag. Detection of either type of RF-ID tags therefore is possible, and the absence of any tag or absence of any valid tag also determined.

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

Abstract: A method and apparatus for transponding pulsed RF signals is provided. The method comprises receiving, with a receiver, pulsed RF signals having a plurality of PRIs. Further the method includes generating, with a PRI tracker, control signals from the received pulsed RF signals. The method then filters the received pulsed RF signals with the control signals to thereby obtain enable signals, which in turn control a transmitter permitting retransmission without clock jitter.

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

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

Abstract: Apparatus for the identification of articles (5) endowed with device for changing the polarization properties of the radiation, comprising a source (1) of non-randomly polarized microwave radiation, and a detector (3) for detecting the change in polarization properties of the radiation. The microwave radiation may have a first plane of polarization and, in use, the device for changing the plane of polarization properties of radiation may change the first plane of polarization to a second plane of polarization. The detector (3) for detecting the change in polarization properties of radiation may comprise a receiving antenna (4c) connected to suitable microwave detector (3), where the receiving antenna (4c) is arranged to favour reception of radiation having the second plane of polarization. For example, the transmitting (4b) and receiving (4c) antennas may be waveguide antennas.

Abstract: A digital RF tag (10) for providing an automatic reply to an electromagnetic signal. The system includes a radar receiver (11, 20); signal and data processors (50, 64) for analyzing the electromagnetic signal to extract data with respect thereto and for synthesizing a second electromagnetic signal; and a radar transmitter (11, 20). The radar receiver (11, 20) is a narrow band radar receiver. The use of a narrow band receiver minimizes power consumption and extends battery life. The inventive RF tag (10) tracks the received radar signal. The data processor (50) includes a microprocessor adapted to execute software designed to implement the tracking function. While the received radar signal is being tracked, type and timing data are extracted and used to synthesize a reply signal. The use of a synthesized reply signal, as opposed to a recorded and modified transmit signal as a reply signal, allows for the transmission of the cleaner (noise free) reply signal.

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

Abstract: 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: A method identifying a set of transponders situated in the interrogation field of analysis apparatus, with each transponder storing a different identity code. The analysis apparatus first transmits data, and each unidentified transponder compares this data with a portion of its own identity code, which portion is selected by the analysis apparatus, and then transmits in a time window, selected at least as a function of the result of the comparison. The analysis apparatus, then receives the data transmitted by the transponders, determines whether data enables any of the transponders identity codes. The analysis apparatus then emits modified data so that after a finite number of iterations the data causes each of the transponders to transmit data enabling the individual transponder's identity code to be determined.

Abstract: An electronic identification system 100 comprises an interrogator 10 and a plurality of transponders 12, 14 and 16. The interrogator comprises a transmitter 11 for transmitting an interrogation signal to the transponders; a receiver 13 for receiving response signals from the transponders; and a controller 19 for processing response signals received, to identify the transponders by their respective response signals. Each transponder comprises a signature generator 35, 32 for generating a unique signature characteristic of the transponder and intermittently transmits, in responses to the interrogation signal, a response signal including the signature. The interrogator further comprises an acknowledgement signal generator 21 for generating upon reception of a response signal from one of the transponders, an acknowledgement signal to be transmitted by the transmitter 11. The acknowledgement signal comprises the signature, thereby to acknowledge reception of the response signal.

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

Abstract: Methods and systems for determining the direction to a transponder are disclosed. The methods and systems include transmitting a first signal to an area where communications with a transponder is desired; producing a second signal desired from the first signal; receiving the second signal via a first and second antenna forming a difference signal from the second signal received via the first and second antennas; forming a third signal by adding the second signal received via the first antenna and the second signal received via the third antenna; delaying the difference signal; and comparing a fist polarity of the delayed difference signal with a second polarity of the third signal.

Abstract: In a system of communicating between a master communication device and a plurality of slave communication devices, the master determines if any of the plurality of slave devices exist within a defined geographic area and, if so sends a bit-by-bit command for the slaves to identify themselves via a unique binary identification number. To avoid collision when the slaves respond, the slaves respond to the master's command within a predetermined period of a time window providing the ID bit by bit. Responses are acknowledged by the master such that only one slave is able to respond with its compute full ID after a bit-by-bit command from the master.

Abstract: A network, sensor and method are provided that utilize the capabilities of impulse radio technology to help monitor and/or control the environment within a building. In particular, the network includes a sensor attached to a first impulse radio unit that is capable of transmitting an impulse radio signal containing sensor related information to a second impulse radio unit. The second impulse radio unit is attached to a control station that uses the sensor related information (e.g., environmental related information, safety related information or surveillance related information) to monitor and/or control the environment within a building. In one aspect of the present invention, the control system can better control and monitor the environment within the building because the sensor may be moved around within the building and reference impulse radio units may interact with the first impulse radio unit to enable the determination of the current position of the sensor.

Abstract: The present invention relates to an internal-pressure detection apparatus for a pneumatic fender that can reduce the labor of maintenance. The internal-pressure detection apparatus is configured of an internal-pressure detection unit 10 provided in a pneumatic fender that is fixed to an underwater structure such as a quay 2 and bridge pier 3 or floated and is used as cushioning material for a ship or the like, and a monitor unit 20 provided in an internal-pressure monitoring station 4 on land. The internal-pressure detection unit 10 is driven by the energy of an electromagnetic wave having a first frequency, and detects internal air pressure of the pneumatic fender 1; transmits this air pressure information by an electromagnetic wave having a second frequency.

Abstract: A communication system, such as an identification system for use in animal feeding or milking parlors, has a driver (16; 200; 320; 350), which supplies current to an antenna (for example 1; 68; 208; 306; 352). That current causes the antenna to emit power (in the from of a time varying magnetic or electromagnetic field), which energizes a transponder (220) operable to transmit an identification signal (such as an RF signal). The driver and antenna are connected to a parallel inductor, which reduces the total inductance of the load seen by the driver. The antenna may be one of a plurality of antennae, all of which are connected to the same driver. Each antenna is located in a respective stall in a milking or feeding parlors so that the system can identify which animal is in which stall of the parlors at a given time.

Abstract: An enhanced backscatter RF-ID tag reader system and multiprotocol RF tag reader system is provided. In a multiprotocol mode, the system emits a non-stationary interrogation signal, and decodes a phase modulated backscatter signal by detecting a stronger phase component from quadrature phase representations or determining phase transition edges in a phase of a received signal. The RF tag reader system predicts or follows the phase of the backscatter signal, thereby avoiding interference from nulls in the received signal waveform due to the non-stationary interrogation signal, relative movement or environmental effects. An acoustic RF-ID tag detection system detects the reradiated signal corresponding to respective transformation of a signal in the tag. Detection of either type of RF-DD tags therefore is possible, and the absence of any tag or absence of any valid tag also determined.

Abstract: A road antenna apparatus includes a road antenna 104 which is mounted on a post 103 and at an elevated position on a road R and establishes radio communication with an on-vehicle radio device 102 mounted in a vehicle 101 which is traveling over the road; and a laser-beam emitting device 111 which is mounted on the road antenna and radiates a laser beam onto a predetermined position 113 on the surface of the road. An offset in the angle at which a road antenna is mounted can be readily ascertained on the basis of a distance between a predetermined position on the surface of the road and a position 114 on the road surface onto which a laser beam is actually radiated.

Abstract: A process and configuration used therein for detecting a transponder in a detection region, structured into two adjacent overlapped cells, provide for detecting the transponder with reference to a particular one cell of the two cells.

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: The invention concerns a receiver designed to pick up an electromagnetic signal, comprising:

Abstract: Interrogators, wireless communication systems, methods of operating an interrogator, methods of operating a wireless communication system and methods of determining range of a remote communication device are provided. According to a first aspect, an interrogator includes communication circuitry configured to output a plurality of wireless signals toward a radio frequency identification device and to receive a plurality of wireless signals from the radio frequency identification device; and a processor coupled with the communication circuitry and configured to determine a range of the radio frequency identification device relative to the interrogator responsive to the received wireless signals.

Abstract: The present invention relates an antenna arrangement (23, 330, 430, 530, 630) comprising a fit layer (331, 431, 531, 631) consisting of a dielectric material and a second reflective layer (335, 435, 535, 640, The dielectric material has variable dielectric characteristics. An electromagnetic radiation (50) passing through said first layer (331, 431, 531, 631) and at least partly reflected by said second layer (335, 435, 535, 640) is modulated by varying said variable dielectric characteristics of said first layer.

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

Abstract: The invention relates to a device for low-frequency communication by magnetic coupling of the type comprising a magnetic field emitter and a receiver placed in an identification member, one of either the emitter or the receiver being furnished with a loop antenna, in which the other of either the emitter or the receiver is constituted by the association of three coils (1, 2, 3) wound around three perpendicular axes (Ox, Oy, Oz) defining a trihedral so as to obtain an omnidirectional magnetic field by supplying said coils with currents of like frequency.

Abstract: An RFID tag's mobility can be increased and cost can be decreased by using high-performance mobile power antennas instead of battery powered tags. Disclosed are some power antennas that include a half wave rectifier, a full wave rectifier, and a voltage multiplier. These antennas can be cascaded to boost the power or voltage gain. Additionally, planar elements can be added to increase efficiency without decreasing mobility.

Abstract: Upon receiving a radar electric wave from a search radar, a radar transponder according to the present invention generates a trigger signal in response to the reception of the radar electric wave. In response to only the trigger signal, the radar transponder starts to generate sweep signals, and continues to generate sweep signals until a stop condition based on an external factor such as stop of power supply or the like is satisfied. Accordingly, the response electric wave can be received with a high probability in the search radar.