Abstract: A system and method for enhancing object state awareness is disclosed. The system includes a receiver subsystem that receives reference signals from an uncontrolled transmitter and scattered transmissions originating from the uncontrolled transmitter and scattered by an object. The system also includes a front-end processing subsystem that determines a radial velocity of the object based on the received transmissions. The system also includes a back-end processing subsystem that determines object state estimates based on the determined radial velocity.

Abstract: A method for determining the location of a high frequency emitter when the location of the emitter is unknown. The signal broadcast from the emitter is observed. Based on the time of the broadcast, the frequency of the broadcast, and the observed signal to noise ratio of the broadcast, it is possible to determine areas where the emitter is likely to be located. Several observations of the signal are compared to find an intersection of all areas where the emitter is likely to be located. The area of intersection is the most likely location of the emitter.

Abstract: A first device (100) transmits a first signal to a second device (300) at a first time. A third device (110) detects a second signal from the second device (300) at a second time. The second signal was transmitted in response to detection of the first signal. Based on the first and second times, a sum of a first propagation delay (200) and a second propagation delay (210) is estimated. The first propagation delay (200) is between the first device (100) and the second device (300), and the second propagation delay (210) is between the second device (300) and the third device (110). The sum of the first and second propagation delays (200, 210) is then used to estimate a location of the second device (300).

Abstract: A RF signal repeater system is added to a wireless communications network which increases user data rates at the periphery of the cellular coverage area by boosting the downlink (base station to mobile user) signal and uplink (mobile user to base station) signal. The RF signal repeater system includes a signal tagging means that adds a unique electronic signature to the repeated signal such that position determination errors due to a non-line of sight propagation path can be corrected. The repeated signal is received and processed with a location measurement unit to determine the time of arrival and to extract the signal tag of the repeated signal. The time of arrival measurement and recovered signal tag are then processed at a mobile location center to determine the true position of the transmitter.

Abstract: This invention relates to a method for calibrating a wireless location system (WLS) to enable the system to make highly accurate differential measurements such as time difference of arrival (TDOA) and frequency difference of arrival (FDOA). Calibration is accomplished by transmitting a signal from an unknown location and measuring at each of two receivers the parameter to be calibrated from that part of the received signal reflected or refracted from an object at a known location in the area. A differential measurement error is determined by comparing the expected difference in the parameter measurements with the actual difference in the parameter measurements. The expected difference is known, a priori, based on the locations of the receivers and the location of the object.

Abstract: A system and method determines the location of a transmitter. At least one receiver receives a signal from the transmitter and at least one proxy receiver is an object that reflects and/or refracts a signal along an arriving path to the at least one receiver. A processor is operative with the at least one receiver and determines the location of the at least one proxy receiver based on one of querying a look-up table or extracting image features from the mapping system and determining the location of the transmitter based on the time of arrival and at least one of angle of arrival of signals from the at least one proxy receiver and transmitter.

Abstract: The location of a transmitter can be determined using a proxy receiver, such as a natural landmark or manmade structure, which reflects and/or refracts the signal from a transmitter toward a receiver. A processor is operatively connected to the receiver and determines the location of the transmitter based on a multilateration calculation that includes the Time of Arrival of the transmitted signal at the proxy receiver and the known or calculated location of the proxy receiver as inputs.

Abstract: A method of determining the position of a transmitting beacon transmitting a signal to certain satellites in a constellation of satellites, which satellites in turn retransmit retransmitted signals to at least one detection ground station, wherein each of said ground stations is provided with at least one antenna whose directional characteristics do not make it possible to identify which satellite retransmitted any given retransmitted signal, and wherein the method implements the following steps:

Abstract: Recently, a smart antenna, i.e., a blind adaptive antenna array, has attracted much attention to suppress multiple access interference (MAI) and multipath signals to improve the capacity of a code division multiple access (CDMA) wireless communications system. Most of the smart antenna algorithms either need matrix computation or complex calculations. In this invented direction-of-arrival (DOA) tracking algorithm only 2M complex multiplications are required per snapshot. Further more the DOA tracking algorithm is not sensitive to the mixer phase distortions. Hence the system complexity is reduced since a separate phase calibration is not required for the DOA tracking algorithm. Also the equivalent DOA tracking error due to the mixer phase distortions is derived. Simulation results show that the DOA tracking algorithm in the present invention works effectively under additive white Gaussian (AWGN) as well as Rayleigh fading environments.

Abstract: A method of processing navigation signals for a satellite navigation system using a receiver. The receiver is provided with a plurality of antennas generating antenna signals corresponding to the reception of signals corresponding to direct paths and to reflected paths. The method advantageously uses: a) a preprocessing of each antenna signal so as to filter it by a matched filter and to take an average over the peaks of the filtered signals; b) a decomposition into singular values in order to make an estimation of a signal subspace from the filtered and averaged signals representative of the correlation peaks; and c) a search for the delays of the signals corresponding to direct paths and to reflected paths.

Abstract: A method and apparatus for determining the location of a mobile unit within a cellular system. A synchronized signal at a common phase is generated at each base station in a system. The mobile unit transmits a signal tone. Each base station compares the phase of the signal tone to the common phase of the synchronized signal to produce a phase offset. A system controller compares the difference between the phase offset of a first base station and the phase offset of a second base station and determines the difference in distance between the first base station and the mobile unit and the second base station and said mobile unit defining a hyperbolic or linear curve of locations. The system controller compares the difference between the phase offset of the first base station and the phase offset of a third base station and determines the difference in distance between the first base station and the mobile unit and the third base station and said mobile unit defining a second hyperbolic curve of locations.

Abstract: A wireless navigational system and process utilize multipath wireless signals normally discarded from the navigation solution to enhance navigational performance under a range of operational scenarios. A relationship between the receiver's location and one or more multipath signals is established, facilitating subsequent navigation using the multipath signal(s).

Abstract: A digital television (DTV) receiver is provided with a sounder comprising a wideband transmitter and a plurality of wideband receivers having separately located receiving antennas, so that the sounder is, in effect, a bistatic radar system for any given channel, in order to characterize a significant nearby, indoor reflector. A microprocessor receives the timing information generated by the wideband transmitter impulses and the reflected impulse returns to each of the receiving antennas, and calculates a multipath model representing the three-dimensional location of a significant, nearby scatterer.

Abstract: The geolocation of a wireless terminal is determined by performing a time/frequency analysis on incoming signals received at a plurality of locations, where each incoming signal includes at least one multipath component of a signal transmitted by the wireless terminal during, for example, regular communications. The time/frequency analysis involves the analysis of the frequency components of the transmitted signal at given instants in time to identify the time-of-arrival of the multipath components of the incoming signal. The time-of-arrival identified for the line-of-sight component of the incoming signal at a plurality of locations can then be processed to determine the geolocation of the wireless terminal.

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.

Abstract: In a method for manipulation of a movable object displayed in a television picture, the distance between the object and fixed basic positions is detected at a time t together with the distance between the object and a television camera in a known position. The object's position is converted to a position X,Y in the television camera's picture plane, generating therein a synthetic object which overlays the movable object and represents it in the television picture. In a method for generating a synthetic track which represents the path of a movable object displayed in television pictures during a period &thgr;, the path of the object is calculated on the basis of its detected positions, and these positions are used for generating a synthetic track which is displayed in a television picture in order to represent the path of the object in the period T.

Abstract: Multipath propagation detection can be accomplished using first and second spaced antennas which receive a carrier signal from a moving radiation source and produce a carrier phase difference representative of the location of the source; a difference signal representative of the difference between the measured carrier phase difference and a predetermined phase difference for the source in that location is generated; and the presence of multipath distortion in that difference signal is determined. Furthermore, when a multiplicity of source signals are tracked as in reception of navigation signals from the Global Positioning Satellite System, the receiver may be programmed to eliminate or suppress errors arising from measurements that have been distorted by multipath propagation.

Abstract: A controller that communicates with a first set of devices and a second set of devices is disclosed. The controller includes a transmitter for transmitting commands to remotely control the first set of devices, and for communicating input/output (I/O) data with the second set of devices. A microphone, speaker, display and cellular and cordless phone circuitry are integrated into the controller to provide the controller with phone and paging capabilities. Systems for determining the spatial location of a target object are also disclosed. The spatial location of the target object is determined with reference to a predetermined spatial reference point based on measured elapsed times, which represent the difference between a time reference and the time of receipt of a location signal from the target object at the known locations.

Abstract: A system and method for enhancing object state awareness is disclosed. The system includes a receiver subsystem that receives reference signals from an uncontrolled transmitter and scattered transmissions originating from the uncontrolled transmitter and scattered by an object. The system also includes a front-end processing subsystem that determines a radial velocity of the object based on the received transmissions. The system also includes a back-end processing subsystem that determines object state estimates based on the determined radial velocity.

Abstract: The characteristics of radio channels are measured. The signals received by a plurality Mc of receiving sensors of a two-dimensional antenna array are composed of wave elements of a transmission signal with regard to the azimuth and the elevation of a different two-dimensional incidence direction and different delay. The transmission signal contains a preselected test sequence, and the incidence angle as well as the delay of the dominant wave fronts are estimated simultaneously taking account of the chip signal form of the test sequence. The signals of each antenna sensor are demodulated, and sampling is then carried out with Mc samples per chip in the test sequence.

Abstract: Apparatus, and an associated method, for determining the geographical positioning of a wireless communication station when the wireless communication station is operated in a non-ideal propagation environment. Errors introduced by NLOS conditions in a determination of a position of the wireless communication station calculated by way of a trilateration technique are corrected. If too few signals are received at the wireless communication station to permit a determination of its position using a ray tracing pattern recognition technique, an estimate of the position of the wireless communication station is also determinable. When implemented in a cellular communication system, accurate position determinations are made even when the mobile station is operated in a non-ideal propagation environment, such as an urban area.

Abstract: A method and system for determining a position of an orbiting transceiver in a communications network includes at least a first and second transceiver at a first and second known location, respectively, on Earth. The first and second transceivers are adapted to transmit and receive communications signals to and from the orbiting transceiver. A processor coupled to one of the first and second transceivers determines a first and second range measurement between each of the first and second transceivers and the orbiting transceiver, respectively, as well as corresponding first and second range rates representative of a time rate of change of the first and second range measurements.

Abstract: A method and apparatus for utilization of GPS, GLONASS or other existing RF signals is disclosed. These existing RF signals are scattered by targets, with a receiver of these scattered signals providing processing to extract three dimensional track of these objects. Angle-of-Arrival (AOA) information of a received signal may be used, but is not required. Modifications of standard GPS signal processing allows observables such as range-sum, range-difference, and bistatic Doppler frequency to be observed. These observables, when coupled with standard bistatic/multistatic location equations, provide unambiguous and even redundant information on target coordinates. The method/device employs a modified code (range)/carrier(Doppler) search routine for initial target search/acquisition, wherein a direct path signal is used as a reference from which chip delay and Doppler shift excursions are examined.

Abstract: An antenna array includes a reference antenna and a plurality of closely-spaced secondary antennas for mitigating the effects of multipath signals on a direct signal, each antenna connected to a corresponding receiver which outputs signal data. A computational device uses the post-correlation signal data to estimate the parameters of a virtual reflector and derive correction values for code data, signal noise, and carrier phase.

Abstract: A method of geoid measurement and/or earth imaging, characterized in that at least one directional antenna (2) is used to pick up a radio signal from a satellite and reflected on the ground, and said signal is processed using a reference signal that corresponds to the radio signal from the satellite in order to obtain a geodesic measurement and/or an image of the zone (Z) towards which the directional antenna (2) is pointed.

Abstract: A radio signal travels over a radio channel in the form of multipath propagation, whereby a signal received by the base station and transmitted by the terminal equipment is composed of multipath components propagated over different distances and thus reaching the receiver at different times. Thus, the information required for computing the bearing of the received signal can be extracted from the arrival time differences of the multipath propagated signal. An antenna array formed by a plurality of antenna elements receives first the multipath propagated signal. Next, means (41, . . . , 4N) for determination of channel impulse response form an estimate of the radio channel impulse response from the received signal of each antenna array element, after which correlation means (46) correlate each channel impulse response estimate with a reference estimate selected from the group of said channel impulse response estimates.

Abstract: A method for determining a geographical location from a measured wireless signal signature comprises calculating from the measured wireless signal signature a multi-dimensional signature vector, wherein each component of the vector measures a degree of coincidence between the measured wireless signal signature and a calibrated signal signature stored in a calibration table. The method also includes matching the signature vector with vectors in a set of multi-dimensional calibrated vectors. The matching uses a procedure comprising searching a hierarchical tree structure and eliminating nodes that cannot contain the best match vector. Within the remaining nodes, the search eliminates individual vectors that cannot be the best match vector, and selects one or more vectors in the set of multi-dimensional calibrated vectors, where the matched vectors correspond to calibrated geographical locations.

Abstract: A method for improving the accuracy of signal signature determinations in wireless location finding systems advantageously uses transmitter velocity estimates to accurately and reliably determine in real time a present signal covariance matrix for a transmitter. In a preferred embodiment of the invention, a method for determining a likely location of a transmitter in a wireless transmitter location finding system comprises coherently measuring transmitter signals received at an antenna array, and calculating a current signal covariance matrix from the measured transmitter signals. The method further comprises calculating an average covariance matrix by forming a linear combination of the current signal covariance matrix with past average covariance matrices.

Abstract: A method of determining the location of an unknown source (10) transmitting an unknown signal to satellite relays (14 and 16) comprises receiving the signal from the relays at respective receivers (18). The receivers (18) receive reference signals via respective relays from a common source (22). The unknown signal and reference signal received by each receiver (18) are processed coherently to preserve their timing and phase information relative to one another independently of signals received elsewhere. The signals are frequency downconverted and digitised, and transferred to a common processing computer (150). The computer (150) performs cross ambiguity function processing of the reference signals to determine their relative Differential Time Offset (DTO) and Differential Frequency Offset (DFO).

Abstract: A vehicular traffic sensor capable of measuring traffic speed and volume in all weather conditions and at a low installed cost. The sensor makes use of multi-path interference of ambient radio frequency (RF) signals. The ambient RF signals can be, for example, control signals constantly transmitted by cellular telephone base stations. As vehicles travel along the roadway, they reflect RF signals in all directions. An antenna mounted near the side of the road will detect signals from the transmitter and signals reflected off the vehicle. Variations in the amplitude of the combination of the two signals can be processed using a method that allows the sensor to determine traffic speed and volume. This information can then be sent directly to a traffic management center. This provides an inexpensive sensor for wide-area traffic monitoring.

Abstract: Method and apparatus for improving the accuracy of a received composite signal s(t) that contains a known reference signal S.sub.d (t) with a known bit transition period .DELTA.tchip and that may contain a multipath signal S.sub.m (t;.chi.;b) with an unknown multipath time delay b and an unknown multipath gain factor .chi. (-1.ltoreq..chi..ltoreq.1). Autocorrelation functions AC(.tau.) and AC(.tau.;d) for the incoming signal and for the reference (direct) signal are determined, dependent upon a time shift variable .tau., and a double difference autocorrelation function .DELTA..DELTA.AC(.tau.)=AC(.tau.)-AC(.tau.-.tau.LE)-AC(.tau.;d)+AC(.tau.-. tau.LE;d) is formed, where .tau.LE is a selected time shift displacement satisfying 0 <.tau.LE.ltoreq..DELTA..tau..sub.chip. Two integrals or sums of .DELTA..DELTA.AC(.tau.) are measured over different selected time shift intervals. The ratio of these two integrals or sums provides a quadratic equation in the time delay variable b that is solved for b.

Abstract: A method and system are provided to produce images of an object. A receiving station is positioned in view of a range-coded signal emitting satellite and the object. The receiving station is sensitive to direct transmission of the range-coded signal and reflections of the range-coded signal from the object. Both range from the receiving station to the object and a Doppler frequency shift history between the receiving station and the object is determined using the direct transmission and reflections of the range-coded signal. An image is formed using the two-dimensional record provided by the range and the Doppler frequency shift history.

Abstract: The invention described herein relates generally to the field of direction finding and source location. The invention has broad application in areas requiring superresolution spectral analysis. The invention described in the context of any array processing problem in which the location of a transmitter is to be determined at a single receiving site based on passive measurements of the propagation waveform. The invention exploits the information received by a pair of sensors to extract intersensor delay and interpath delay times in the presence of multipath propagation. Two sensors are used in order to normalize the effects of signal modulation. Combining the sensor pairs in groups, the direction-of-arrival may be determined for each signal from the intersensor delay times thus derived. The invention additionally provides for the estimation of transmitter location by using the intersensor and interpath delay times.

Abstract: A system for measuring the relative positions of first and second units includes a re-transmitting apparatus at the first unit and a receiver at the second unit capable of making simultaneous real-time comparisons of phase and frequency information contained in first signals received directly from the satellites by the second unit and second signals received from the satellites by the first unit and immediately retransmitted to the second unit in their entirety without processing before retransmission.

Abstract: A direction finding method and system for locating the direction of a transmission source based on an electromagnetic wave which is transmitted from the transmission source and is received by an antenna means at a receiving end apparatus. The transmission source transmits an angle-modulated wave. Meanwhile, the receiving end apparatus receives the transmitted wave, converts into electrical signals a beat frequency signal which is caused by direct and reflected waves contained in the received wave, and time-averaging the electrical signals, thus minimizing a angle error due to a multipass interference.

Abstract: A method of passive ranging and geolocation of multiple emitters by a single detection platform. Two independent emission sequences support formulation of two independent algebraic equations involving a triangular arrangement of platform and emitters. One sequence constitutes an interrogation signal by one emitter and a transponded or reflected signal from another. A second emission sequence constitutes the reversed order of emitters from those of the first emission sequence. The method utilizes the steps of measuring the time difference of arrival at the platform of signals having travelled the direct path and the transponded or reflected paths, and measuring the angles of arrival of received signals for each independent emission sequence. A series of steps computing ranges and angles based on prior measurements provide a set of desired ranges and angles identifying the relative positions of the emitters relative to the platform.

Abstract: A radar system for passive determination of range to a non-cooperative scanning radar, to a non-emitting object illuminated by the scanning emitter and between scanning emitter and illuminated object entirely from the passive location. The radar equipment at the passive location includes a passive array with beam forming and switching matrix to provide output signals separately on the basis of angular discrimination, for each of the object and emitter. Resolver circuits respond to the angle between emitter and object vector, the incremental time between direct emitter reception and reflected echo from the object as well as to emitter scan rate and instantaneous pointing angle. Algorithms for the emitter range, object range and range between emitter and object are given.

Abstract: A tristatic radar tracking system is disclosed in which two remote transmitters and a radar receiver use a method for combining measurements of the Doppler frequency shift and angle of arrival of two signals scattered by a moving target to derive parameters of the target's trajectory through space.

Abstract: A passive surveillance method and system, capable of operation in conjunction with both non synchronous and synchronous pulse pattern rotating ground radars. Received signal scan modulated pulses are deinterleaved and correlated with a previously selected repetitive portion of an interrogation signal source base pulse pattern. A single receiver channel, sequential lobe on receive only (LORO) direction finding antenna is employed in the system to modulate received signals to extract target object relative bearings for the correlated signals. The system makes use of all available data to determine the best estimate of the target object position.

Abstract: A passive self-determined position fixing system for use by aircraft and other users such as sea-going vessels utilizes a directional radar in combination with an omnidirectional radar facility to produce a directional radar beam and simultaneous omnidirectional radar transmission. A television type broadcast facility provides a broadcast of the PPI display of the directional radar system. The directional radar pulse signals together with the omnidirectionally retransmitted radar pulse signals are processed by the position fixing system aboard the host aircraft or the like to determine range information. A display system such as a conventional television receiver responds to the broadcast PPI display to produce a similar display within the host aircraft. The position fixing system combines the PPI type display together with the information with the directional and omnidirectional radar transmissions to identify the user or host aircraft or vessel upon the PPI type display.

Abstract: An accurate location system 10 for use in locating the position of a tracked unit 16 having at least a first and a second transmitter 14, 22 for propagating at least first and second signals and a master station 12 for receiving and storing the first and second signals, respectively. The tracked unit 16 receives and operates on the first and second signals from the first and second transmitters 14, 22, respectively, for providing third and fourth signals which are transponded to the master station 12. A correlation detector 40 located within the master station 12 receives and cross-correlates the transponded third and fourth signals with the stored first and second signals within the master station for determining the additional times of flight (.tau.) of the third and fourth signals transponded to the master station. The locus of points of constant (.tau.

Abstract: A passive ranging system for determining the slant range from a ground station to a drifting radiosonde. In one embodiment, the ground station receives meteorological data ranging and internal temperature signals from the radiosonde. The data signals are read out as ambient conditions of the atmosphere and the range signal is phase-compared to a reference signal at periodic intervals. Changes in frequency due to temperature fluctuations in the radiosonde components are factored into the phase-comparison, and the resultant change in phase represents movement of the radiosonde. In another embodiment the range tone from a remote broadcast station is retransmitted by the radiosonde and received at the ground station simultaneously with the same tone directly from the broadcast station. The phase lag is measured and coupled with measurements of direction from the ground station to the radiosonde, and with the distance between the ground station and the broadcast station for determining the slant range.

Abstract: A system for locating a transponder (10) to an accuracy of plus or minus about 10 m in an area about 5 km across includes a master station (12) and two slave stations (14, 16) at known positions. The transponder and the two slaves each incorporates an electronic flywheel circuit and means to bring it into synchronism with a synchronizing signal from the master station. After a preset delay the transponder then transmits a radio signal to be received by the slave stations and by the master station, the time of receipt of which is measured at each. From these times the location of the transponder (10) is determined by a computer (18).

Abstract: A system and method for determining the position of an airborne object, using a fixed station and a pair of earth orbit satellites whose positions are known. Separate periodic signals are transmitted from the fixed station via the first and second satellites to the object whose position is to be determined. The phase offset in periodic characteristics of the periodic signals as received from the first and second satellites is measured at the object. The phase offset corresponds to a realtive time difference in propagation of the signals traveling two different paths to the object. The object transmits via the first satellite a return signal indicative of the measured relative time difference. This return signal is activated some time in the future according to the object local time, which is slaved to receipt of the periodic signal sent through the first satellite. This future time is the start of the particular time period as decided by the fixed station's schedule.

Abstract: A multistatic radar system is provided in which a transmitter radiating high-frequency radio waves is mounted on a flying object adapted to be launched into the sky, whereby the range of the radar system is improved.

Abstract: The lightning range system for determining distance between a lightning discharge and an airborne object includes a receiver on the airborne object adapted to receive electromagnetic radiation signals generated by a lightning discharge along both a direct and a surface reflected path. Signal processing apparatus is interconnected with the receiver for determining the difference in the time of arrival of the direct and reflected signals. A computer is provided to calculate the range of the lightning discharge from the difference in the time of arrival of the direct and reflected signals. In a preferred embodiment, the signal processing apparatus is digital and includes at least a 10-bit analog-to-digital converter with at least a 36 megahertz sampling rate.

Abstract: A radio position determation and message transfer system is implemented using a pair of satellites in geostationary orbit for replaying interrogation and replay signals between a ground station and a user-carried transceiver. The user portion is calculated based on the arrival times of replay signals received at the ground station via the two satellites, the known transmission time of the interrogation signal from the ground station, and the user's elevation on the surface of the earth. The elevation is derived from a stored terrain map providing local terrain elevations at a plurality of points of the earth's surface. The stored terrain map allows accurate position fixed to be obtained for surface users regardless of the deviation of the local terrain from the spherical or ellipsoidal model of the earth's surface.

Abstract: A radio frequency emitter transmits pulses in a regular swept beam pattern. As a result of this regular pattern, the angles of transmission of the pulses can be inferred. Intervisibility data of terrain points in a region around an observation point are stored in computer memory. At the observation point, measurements are made of the times of arrival of a plurality of terrain point reflections of a single pulse transmitted by the emitter. These measurements are repeated for a plurality of pulses transmitted by the emitter. In a computer, a comparison is made of the terrain points of reflection calculated from the measured times of arrival for assumed emitter locations with the stored intervisibility data of terrain points.

Abstract: A method and apparatus is disclosed for passively determining altitude above the ground of an aircraft by use of an active emitter carried on a second higher altitude aircraft. Specifically, the altitude of the aircraft is determined by measuring the time difference between direct path radiation and reflected path radiation, taking into account the distance between an upper antenna which receives the direct path radiation and a lower antenna which receives the reflected path radiation and the angles of travel relative to the vertical between the direct path radiation and the reflected path radiation.

Abstract: An improved vehicle or other object-tracking and location system, preferably, though not essentially, of national scope, wherein transponder or transceiver-equipped stolen or missing vehicles or other objects may be located and/or tracked, as by appropriately-equipped police direction/finding tracking vehicles, through homing-in on periodic transponder reply radio transmissions automatically activated by command activation signals broadcast on the same carrier frequency as the transponder reply signals and with encoded vehicle identification information that causes the intended vehicle transponder so to reply, and with provision for modifying the command signals to require an increased rate of periodic transponder reply signal transmission to assist homing-in on the selected vehicle.