Abstract: In a geolocation system for determining a geolocation of a target emitter, a method for determining the geolocation. The method comprises receiving a signal transmitted from the target emitter at each one of a plurality of sensors; determining whether signals received at n sensors, from among the plurality of sensors, satisfy one or more threshold values related to a condition of the received signals; if signals received at n sensors satisfy the threshold value, commanding m of the n sensors to transmit the signal received thereat or information related to the signal received thereat to a processor; at the processor, determining time difference estimates for the m received signals and determining the geolocation of the target emitter from the time difference estimates.

Abstract: A location system comprising a plurality of base units for enabling the locating of a device by means of one or more location signals communicated between the device and the base units and signal processing equipment for: i. determining the location of the device in dependence on the manner in which the location signal(s) is/are received and ii. deriving calibration data for calibrating the system in dependence on the manner in which the location signal(s) is/are received.

Abstract: In a multilateration apparatus a correlator is provided with a time of arrival correlation window which is set to cater for the path lengths that may be experienced before a signal from an object to be located is received by receivers in the system. This may be on the basis of the largest possible path length in the system or on a receiver by receiver basis.

Abstract: Apparatus having corresponding methods and computer-readable media comprise a first receiver to receive a wireless television signal; a first measurement unit to generate a measurement of the wireless television signal; wherein a position of the apparatus is determined based on the measurement of the wireless television signal; a second receiver to receive a wireless local area network (WLAN) signal; and a second measurement unit to generate a measurement of the WLAN signal; wherein a position of a transmitter of the WLAN signal is determined based on the position of the apparatus and the measurement of the WLAN signal.

Abstract: A multilateration system and method includes a plurality of receiver stations for receiving signals from an aircraft, and a controller that derives the position of the aircraft by applying a multilateration process to outputs from the receiver stations. For this purpose, the controller determines the altitude of the aircraft and selects a multilateration process that is to be used for position determination, based on the determined altitude.

Abstract: A Wide Area Sensor Network (WASN) is disclosed that utilizes wideband software defined radios (SDRs) to monitor RF energy over a wide frequency range, detect when critical frequencies are being jammed or otherwise interfered with, and locate the source of the interference so that the interference can be eliminated. The WASN may use one or more geolocation techniques In addition, the WASN may detect and locate unauthorized transmitters as well as estimate the transmitted power of authorized transmitters to assure they are not transmitting more power than authorized.

Abstract: A method and system determine a location of an emitter using at least three sensors, each receiving a signal from the emitter. Cross-correlation data is determined for the received signals at sensor pairs, and one or more peaks are identified in the cross-correlation data. A likelihood function is determined for each sensor pair. A total likelihood function is determined for the sensors using the likelihood functions for each sensor pair, and the location of the emitter is determined as the point where the total likelihood function is maximized. The individual likelihood function for each sensor pair can be determined by selecting, at each point in a grid, a peak in the cross-correlation data that generates a minimum residual according to a minimum residual criterion, and using the selected peak in the cross-correlation data for each point in the grid to calculate the likelihood function.

Abstract: A method for determining a transmission timing is provided. The method includes steps of, at a first point in time, determining a first transmission timing for transmissions from a user entity to a first radio transceiver, and determining a representation of a first position of the user entity in relation to the first radio transceiver and at least a second and a third radio transceiver. The method further includes, at a second point in time, subsequent to the first point in time, determining a representation of a second position of the user entity in relation to the first, second and third radio transceivers, and adjusting the transmission timing based on a difference of the first position and the second position.

Abstract: A system of determining a position of a mobile device within a surveillance volume includes a phase difference array comprising a spatially diverse array of N sensors for detecting RF signals from the mobile device and acquiring phase difference data from the RF signals, N being greater than 4. The system includes a processor for processing the phase difference data and determining the position of the mobile device from the phase difference data.

Abstract: Estimating a current location of a receiver in a MediaFLO™ (Forward Link Only) mobile multimedia multicast system comprises receiving digital signals comprising a MediaFLO™ superframe comprising orthogonal frequency division multiplexing (OFDM) symbols; performing slot 3 processing of each medium access control (MAC) time unit of a data channel to identify a transmitter identity (TxID) of each transmitter; identifying corresponding geographical coordinates of each TxID; regenerating the digital signals for each of the transmitters using a local-area differentiator (LID) and a wide-area differentiator (WID) of the transmitters; dividing the digital signals by the corresponding regenerated transmitted signal to obtain channel estimates between the receiver and the corresponding transmitters; detecting a first peak in the channel estimates to determine a distance between the receiver and the corresponding transmitters; calculating a time difference of arrival of the digital signals; and estimating a current loca

Abstract: Mechanisms are provided for determining the location of a stylus for a portable electronic device. One embodiment provides for determining at a first time that a stylus was not returned to a stylus receiver of the portable electronic device and determining last usage information relating to a last usage of the stylus at a second, earlier time. The embodiment may further include storing by the portable electronic device the determined last usage information and determining stylus location information based on the last usage information. The embodiment may further include providing an indication of the stylus location information to a user. Stylus location information may include one or more of a physical location, a geographic location, a calendar event associated with a last usage, directions to a place of last usage, an application being used at last usage of the stylus, or a user identity.

Abstract: A method and system for determining a location of a first device that emits a signal: provide at least three sensors separated and spaced apart from each other; determine estimated location data for the first device for each sensor or unique sensor pair; determine an estimated location of the first device using the estimated location data for each sensor or unique sensor pair; determine residual values for the estimated location data for each sensor or sensor pair; convert the residual values into corresponding weights for the estimated location data for each sensor or sensor pair; weight the estimated location data for each sensor or sensor pair by its corresponding weight; and update the estimated location of the first device using the weighted estimated location data for each sensor or sensor pair.

Abstract: A method and apparatus for estimating bias errors in a time-difference-of-arrival/frequency-difference-of-arrival (TDOA/FDOA) geolocation system using a reference signal transmitter in which position and/or motion information of the reference signal transmitter is encoded into the reference signal. The motion information may include the velocity and/or acceleration of the reference signal transmitter. The reference signal is received by multiple collection platforms operating in conjunction with a geolocation system and a reference correction processing system. The reference correction processing system receives, via the multiple collection platforms, the position and/or motion information, which is immediately and unambiguously associated with specific reference signal transmissions. The geolocation system estimates the position and/or velocity of the reference signal transmitter using conventional TDOA/FDOA techniques.

Abstract: An area estimation apparatus 100 includes: a reception level receiving unit 110 configured to receive, from a plurality of the radio signal capturing terminals 40a and 40b via the network, a radio signal reception level transmitted from the radio signal transmitting terminal 10, a radio signal transmitting terminal ID for uniquely identifying the radio signal transmitting terminal 10, and a radio signal capturing terminal ID for uniquely identifying each of the plurality of radio signal capturing terminals 40a and 40b; with a presence area of the radio signal capturing terminals being known; a reception level storage unit 123 configured to store the radio signal reception level, the radio signal transmitting terminal ID and the radio signal capturing terminal ID, which are received from each of the radio signal capturing terminals 40a and 40b, in association with one another; and a presence area estimating unit 140 configured to refer to the reception level storage unit and to estimate the presence area of th

Abstract: A system and method for estimating the position of wireless devices within a wireless communication network combines measured RF channel characteristics for the wireless device with one or more predicted performance lookup tables, each of which correlates an RF channel characteristic to some higher order network performance metric and/or a position within an environmental model. Measured RF channel characteristics for wireless devices are compared against the performance lookup tables to determine the sent of lookup tables that most closely match the measured RF channel characteristics. The positions within the environmental model corresponding to the selected set of matching lookup tables are identified as possible locations for the wireless device. The performance lookup tables are uniquely constructed by site-specific location, technology, wireless standard, and equipment types, and/or the current operating state of the communications network.

Abstract: A method for determining a position of a wireless electronic device within a volume includes detecting a signal transmitted by the wireless device during two-way communication to and from a first known position within the volume. The method further includes detecting the signal from at least three additional known positions within the volume, where the at least three additional known positions are spatially independent of each other. The method further includes determining a phase difference between the signal detected at the first position and the signal detected at each of the at least three additional positions, determining the position of the wireless electronic device using the phase differences, and at least one of displaying and storing the position of the wireless electronic device.

Abstract: A system and method for detecting and locating a radio frequency emitter. A number, N, of receiving units using the same bandwidth, center frequency, and measurement time duration receive signals from the emitter. Higher Order Statistics (HOS) are used to calculate a correlation function between the received signals using one of the received signals as a reference. Results of the correlation function are used to form volumes of probabilities in a subset of an N?1 dimensional space of information regarding the location of the emitter. Each correlation function result in the subset corresponds to a single point in physical space.

Abstract: Systems and methods for facilitating a first response mission at an incident scene, such as an accident site, a natural or human-made disaster site, or any other first response site. One system is for locating a plurality of portable modules at an incident scene. The system comprises a plurality of receivers transportable to the incident scene. The system also comprises a processing entity configured to: determine a location of a first one of the portable modules based on first data derived from a wireless signal transmitted by the first one of the portable modules and received by at least three receivers of the plurality of receivers; and determine a location of a second one of the portable modules based on the location of the first one of the portable modules and second data derived from a wireless signal transmitted by the second one of the portable modules and received by the first one of the portable modules.

Abstract: The present invention relates to a system 10 and corresponding method for locating mobile terminals 12 following a location request whereto is associated information whose content depends on the position and characteristics of the mobile terminal 12 to be located. The system 10 comprises a cellular phone location centre (MLC centre) 15 able to locate the mobile terminals 12, in selective fashion, as the type and reliability of the received information vary. The system 10 and corresponding method allow, by means of the MLC centre 15, to select, among a plurality of location engines, a determined engine suited to manage the received information and selectively to identify both the position of the mobile terminal 12 and accuracy indicators relating to the type of locating operation performed.

Abstract: A real-time, multi-sensor local-area lightning detection network system. The system uses waveform indicative of electrostatic field changes with respect to time is generated at each of N locations due to a cloud-to-ground lightning strike occurring in the vicinity of the N locations. Each waveform is integrated to generate a corresponding electric field associated with a corresponding one of the locations. A mathematical relationship is used to determine a ground surface location of the lightning strike, height of the lightning strike, and charge per unit length of the lightning strike using each electric field generated during integration of the waveforms.

Abstract: A method and system for positioning mobile units using angle measurements taken by neighboring mobile units is disclosed. A selected mobile unit and mobile units in the vicinity of the selected mobile unit are selectively instructed to measure and report information related to the position of the selected mobile unit. The reported information is used to compute a position of the selected mobile unit.

Abstract: Issuance of work orders in response to monitoring signal egress from shielding integrity flaws in a cable communication system by detecting received signal strength from a mobile receiver only during rising trends in received signal strength when the mobile receiver is in motion and tracking the maximum received signal strength peak during each rising trend. Rising trends are detected by computing two rolling averages of received signal strength sample of different lengths and offset from each other and applying a threshold to the difference between the rolling averages to provide hysteresis in switching between rising and falling trend detection. Reported peaks are then compared by proximity to each other and their circle of influence determined in accordance with respective signal strengths to determine if newly reported peaks are duplicates of previously reported peaks and duplicate reported peaks are removed or discarded.

Abstract: Systems and methods are presented for passive location of transmitters in which two or more receivers time stamp received signals from target transmitters and the time stamped data for each target signal of interest is isolated to identify a peak power time of arrival for the signal at each transmitter from which differential scan observation values are derived, and for each signal of interest a line of position curve is computed based on the differential scan observation value and corresponding receiver locations, and for each signal of interest an estimated target transmitter location is determined based on an intersection of two corresponding line of position curves.

Abstract: In a multilateration system receivers are grouped into two groups. The first group is used to determine a position of a signal source, for example, an aircraft equipped with a SAR transponder. From the determined position, predicted time of arrival values are produced for the second group receivers. These are compared with the actual time of arrival values for the signals arriving at the second group receivers. A difference is determined and then the variation of that difference is determined as the aircraft travels in its track. The groupings are then varied and further variations determined. When the minimum variation is determined an alert is given that the second group has a receiver which is operating with a larger than desirable group time delay.

Abstract: At least two receiver sets are provided. A data processor is in communication with the receiver sets, wherein the data processor tags position data and radio frequency emission data from the receiver sets. A data storage unit is in communication with the data processor and is at least capable of storing tagged data. A processing unit is capable of processing the tagged data. The processing unit defines a search grid within which to search for the source of the radio frequency emission. The processing unit motion compensates the tagged data separately for each point on the grid. The processing unit assigns a value to each grid point based on a phase coherence of the motion compensated data. The processing unit determines a location within the grid having a highest assigned value, thereby determining the source of the radio frequency emission.

Abstract: A system for geolocating a radio frequency (RF) transmitter in the presence of multipath interference may include a plurality of RF receivers arranged in spaced relation. The system may also include a controller coupled to the plurality of receivers and configured to generate a plurality of measurements associated with the RF transmitter. The controller may also compute a plurality of ambiguity functions based upon the plurality of measurements and due to the multipath interference, and project the plurality of ambiguity functions onto a common geo-referenced grid. The controller may also detect a peak on the common geo-referenced grid indicative of a geolocation of the RF transmitter.

Abstract: A method for enabling a system to enhance the accuracy of a location estimate modifies weights in a weight matrix associated with receiver station measurements in parallel with successive refinements of the location estimate. In a typical location estimation scenario, several receiving stations simultaneously derive measurements of a signal from the emitter. Any one of these measurements is in general some function of the emitter location and the receiving station location. The aggregate of these measurements is often in excess of the minimum number of measurements required to provide an estimate of the emitter location. Where such an excess exists, the method proceeds by modifying the weights associated with the measurements in parallel with successive refinements of the location estimate. The method can be implemented over various cellular protocols with a consistent and significant enhancement in the accuracy of location estimates.

Abstract: Method of locating one or more transmitters on the basis of an array of sensors moving with respect to the transmitters comprising at least the following steps: determining the direction vectors âk corresponding to the response of the array of sensors to a source with incidence (?, ?) as a function of the incidence parameters ?, ?, and of the parameter ? related to the distortion of the phases on the sensors, transforming this vector âk so as to eliminate the unknown parameter ?, into a vector ?km, ??km, using the transformed vector to obtain the position of the transmitter using a maximized locating criterion.

Abstract: Methods and apparatus related to peer to peer communication networks are described. An active connection list is maintained by a wireless communications device supporting peer to peer communications. In various embodiments, the active connection identifier list being maintained is in addition to a list of discovered peers in the local vicinity. Paging signaling, e.g., peer to peer paging signaling, is used to establish active connections. Air link peer to peer traffic resources include traffic control resources and traffic data resources. A wireless communications device seeking to transmit on a traffic data resource transmits a traffic request signal on a traffic control resource. An active connection identifier is, in some embodiments, associated with a particular subset of traffic control resources. Thus, a wireless communications device monitors the portion or portions of the traffic control resource corresponding to its active connections for traffic request signals, but need not monitor other portions.

Abstract: In a multi-radar system, configured comprising a plurality of radar units which generate and output signals the frequency of which increases and decreases periodically, each radar unit generates and outputs signals synchronized with a prescribed sync signal, such that the upper limit and lower limit of the periodically increasing and decreasing frequency is different for the signals of each radar unit, and moreover the timing of the upper limit and lower limit of the signals substantially coincide. By this means, the frequency intervals between signals can be reduced, and more channels can be set, without causing radio wave interference.

Abstract: The location of a medical device is determined by receiving one or more signals at the medical device transmitted by one or more beacons, respectively, at known locations. The one or more signals received at the medical device are sent from the medical device to a processor, which determines the location of the medical device based on the received one or more signals. One of the beacons may be a portable patient beacon, the location of which is determined when its signal is received by a medical device, the location of which was previously determined.

Abstract: Multilateration techniques are used to provide accurate aircraft tracking data for aircraft on the ground and in the vicinity of an airport. From this data, aircraft noise and operations management may be enhanced. Aircraft noise may be calculated virtually using track data in real-time and provided to a user to determine noise violations. Tracking data may be used to control noise monitoring stations to gate out ambient noise. Aircraft emissions, both on the ground and in the air may be determined using tracking data. This and other data may be displayed in real time or generated in reports, and/or may be displayed on a website for viewing by airport operators and/or members of the public. The system may be readily installed in a compact package using a plurality of receivers and sensor packages located at shared wireless communication towers near an airport, and a central processing station located in or near the airport.

Abstract: Various aspects of the present invention are shown and described, each of which has stand alone utility in a navigated medical environment. A receiver position calibration system and method facilitates calibration of a reference frame prior to each navigated procedure. A concept and application of confidence weights is introduced. Confidence weights can be applied to distance calculations to mitigate the effects of interference and increase the tolerance of the navigated medical system. Multi-path interference is minimized through the transmission of a signal having a pattern of unique frequencies and filtering of the distance calculations for each frequency to identify the ‘best’ distance in the presence of multi-path interference. A position determination method and system that transmits a signal having multiple frequency components permits positions to be identified with high resolution over a large area.

Abstract: A method of multilaterating the position of a target, including the steps of deploying a plurality of time synchronized receiving units in a network that allows the receiving units to communicate with a central processor; receiving a target signal from the target at each receiving unit; determining a time of arrival for the target signal at each receiving unit; determining position data for each receiving unit at the time when the target signal is received at each respective receiving unit; and using the time of arrival and position data for each receiving unit to determine the position of the target by multilateration. A system for carrying out the method is also disclosed.

Abstract: Techniques are disclosed that allow for the detection, identification, direction finding, and geolocation of emergency personnel in a given multipath environment. For example, the techniques can be used to detect and identify multiple lines of bearing (LOBs) to an IEEE 802.11 emitter of an emergency responder that is inside a building or otherwise hidden from view. LOBs from multiple vantage points can be used to geolocate and/or track the emergency responder. The resulting geolocation can be plotted on a map display or model of the scene (e.g., building, etc) so the precise position of the emergency responder having the targeted wireless emitter can be known.

Abstract: A method of multilaterating the position of a target, including the steps of deploying a plurality of time synchronized receiving units in a network that allows the receiving units to communicate with a central processor; receiving a target signal from the target at each receiving unit; determining a time of arrival for the target signal at each receiving unit; determining position data for each receiving unit at the time when the target signal is received at each respective receiving unit; and using the time of arrival and position data for each receiving unit to determine the position of the target by multilateration. A system for carrying out the method is also disclosed.

Abstract: Method of using one or more transmitters and/or one or more parameters associated with a transmitter by using a reception station comprising a device suitable for measuring over time a set of K parameters dependent on the transmitters associated with vectors {circumflex over (?)}k representative of the transmitters for 1?k?K. The method includes a step of extracting the parameter or parameters consisting in grouping together by transmitter the parameters which are associated therewith by means of a technique of independent component analysis.

Abstract: A portable location device for use in a location system, the device comprising a transmitter for transmitting ultra-wideband signals, a receiver for receiving non-ultra-wideband signals and a control unit coupled to the receiver for controlling the operation of the device in dependence on the received non-ultra-wideband signals.

Abstract: To cater for the positioning of an aircraft in a boundary zone between two adjacent multilateration systems, the controller (14) in one system receives Time Difference of Arrival data provided by the controller (15) in the second system. The controller (15) derives the TDoA data from time of arrival data provided by its receiver stations (9-13). By furnishing TDoA data the timings of the two systems do not need to be synchronised. The controller (14) uses the TDoA data and also time of arrival data from its local receiver stations (4-8) to perform a multilateration to determine the location of the aircraft (16).

Abstract: An apparatus and method for locating a terminal in a broadband wireless communication system are provided. The apparatus for locating the terminal includes a candidate region determiner, a virtual location determiner, and a final location determiner. The candidate region determiner determines a candidate region of the terminal by using tag signal arrival time information of the terminal provided from a plurality of readers. The virtual location determiner determines a virtual location of the terminal in the candidate region in consideration of a propagation delay of the tag signal. The final location determiner predicts a tag signal arrival time from the virtual location and determines the virtual location as the final location if a difference between the predicted tag signal arrival time and a measured tag signal arrival time is less than or equal to a threshold value. The apparatus and method provide a less expensive and less complex locating system.

Abstract: Iterative geolocation of a stationary RF emitter through the use of TDOA may include the use of a single portable geolocation (e.g., TDOA) sensor, a pair of portable geolocation sensors and three of more portable geolocation sensors. Adding portable geolocation sensors to the iterative process reduces the constraints on the signals to be located as well as providing a reduction in the number of iterations required to obtain improved location accuracy.

Abstract: Embodiments of the present invention include a method of determining a location of a mobile device. The method comprises transmitting a signal between a plurality of known locations and receiving signal at device of unknown location such as a mobile device. The signal may include multiple tones having different frequencies and resulting in sets of residual phase differences. The location of the mobile device may be determined using the known locations and the frequency and phase differences between the transmitted tones. In one embodiment, OFDM signals may be used between an access point and mobile device, for example, to determine the location of the mobile device.

Abstract: A system, method, and article of manufacture for locating or communicating with a patron at a hospitality facility includes a server and a plurality of client terminals. The server may receive, from one of the plurality of client terminals, a patron identifier identifying a patron and a location identifier identifying a location in the hospitality facility and storing the location identifier in an account corresponding to the patron identified by the patron identifier. A patron, using a client terminal may send a request for the location of a particular patron to the server. The server retrieves, from an account corresponding to the particular patron, a location identifier for the particular patron and sends a message based on the location identifier for the particular patron.

Abstract: There is disclosed a system for identifying a source location of an electromagnetic signal having a known waveform. Radio receiving equipment located at three of more monitoring stations receives and demodulates a radio frequency signal from a common source. A time stamp generator applies a time stamp to each block of N digital data samples derived from the received radio frequency signal at each monitoring station. A GPS timing signal can be used to synchronize the time stamp generator in each monitoring station. Further, replica generating hardware and/or software at each monitoring station periodically synchronously generates a replica waveform. An autocorrelation processor at each monitoring station determines a time offset between an occurrence of the known waveform in the signal, and an occurrence of the replica waveform at each monitoring station.

Abstract: A position detecting system includes an RFID terminal configured to transmit an identification information signal by radio; a plurality of receiving devices configured to receive the identification information signal; and a position detecting server configured to receive a reception notification of the identification information signal from each of the receiving device and configured to estimate a position of the RFID terminal. The RFID terminal includes a part configured to perform radio transmission of a plurality of identification information signals having different radio strengths. The position detecting server includes a part configured to integrate the reception notifications of the identification information signals having different radio strengths and configured to estimate the position of the RFID terminal.

Abstract: Apparatus having corresponding methods and computer-readable media comprises: a first receiver adapted to receive, at a user terminal, a broadcast television signal from a television signal transmitter; and a second receiver adapted to receive, at the user terminal, a satellite positioning signal from a positioning satellite; wherein a position of the user terminal is determined based on the broadcast television signal, the satellite positioning signal, a location of the television signal transmitter, and a location of the positioning satellite.

Abstract: An ultra wideband (UWB) or short-pulse RF system is disclosed that can be used to precisely locate or track objects (such as personnel, equipment, assets, etc.) in real-time in an arbitrarily large, physically connected or disconnected, multipath and/or noisy environment. A system implementation includes multiple zones or groups of receivers that receives RF signals transmitted by one or more timing reference tags and one or more objects having associated object tags. Each zone or group may share a common receiver. By combining a multiple reference tag system with a virtual group of receivers, i.e., a zoning technique or system, a cost-effective system can be provided that offers scalability and flexibility to monitor a significantly expanded coverage area.

Abstract: In a Wireless Location System (WLS) deployed in connection with a CDMA-based wireless communications system, Location Measurement Units are used to collect multi-path corrupted radio signaling for use in time difference of arrival (TDOA) and hybrid positioning methods. Signal processing techniques are used to enhance the WLS's ability to determine the minimally time-delayed multi-path component and thus increase the accuracy of the TDOA location in CDMA-based wireless communications systems. The signal processing includes a filtering technique for reducing the leading sidelobes of the cross-correlation function as well as a leading edge discovery procedure.

Abstract: A method and apparatus for determining a location of a transmitter includes taking a Received Signal Strength (RSSI) measurement at a plurality of locations. Next, a known transmit power is subtracted from each of the RSSI measurements to produce a Propagation Loss Vector (PLV) for each location of the plurality of locations. A model is developed from the PLVs, the model including a plurality of grid points. A candidate Transmit Power Vector (TPV) is produced by subtracting the PLV for a candidate location from the RSSI measurement. Each of the RSSI measurements are matched against each TPV of the model. Once all the grid points have been evaluated, the grid point having a best match is selected as a location of the transmitter.

Abstract: Communication between a remote locator and a transponder is used to determine the relative position of the transponder. The transponder and locator each include a transmitter and a receiver. The locator transmits an inquiry in the form of a relatively powerful cyclically encoded signal with repetitive elements, uniquely associated with a target transponder. Periodically, each transponder correlates its coded ID against a possible inquiry signal, determining frequency, phase and framing in the process. Upon a match, the transponder transmits a synthesized response coherent with the received signal. The locator integrates multiple cyclical response elements, allowing low-power transmissions from the transponder. The locator correlates the integrated response, determines round-trip Doppler shift, time-of-flight, and then computes the distance and angle to the transponder. The transponder can be wearable, bionically implanted, or attached to, or embedded in, some object.