Abstract: Apparatus for determining positional information relating to an object, comprising: means for receiving, comprising a plurality of receiving elements; detection means for detecting signals received at the receiving elements and for generating output signals representative of the received signals; and processing means operable to apply, for each receiving element, a process to the output signal generated from the signal received at that receiving element separately from any output signal generated from a signal received at any other receiving element, so as to obtain a respective value of a parameter representative of the signal received at that receiving element, the processing means being further operable to compare the values of the parameter thus obtained so as to, obtain positional information relating to the object.

Abstract: A method and apparatus for encoding information in a reference beacon signal for use in a time-difference-of-arrival/frequency-difference-of-arrival (TDOA/FDOA) geolocation system. Information is encoded in the reference beacon signal using variations in the times and frequencies of sequential reference signal transmissions. The encoded information may include an identifier associated with the transmitter of the reference beacon signal. A geolocation system receiving the reference beacon signal can thus differentiate it from non-cooperative target emissions as well as from other reference beacon signals.

Abstract: Disclosed is a wireless positioning system and method that can perform a high-precision position tracking. The wireless positioning system includes a target device that is an object of wireless positioning, beacon devices and a processing unit. The beacon devices transmits wireless signals and sense reception time points of the wireless signals transmitted from the other beacon devices and the target device and received at time points after the transmission of the wireless signal. The target device receives the wireless signal transmitted from at least one of the beacon devices, and then transmits the wireless signal to the beacon devices. The processing unit obtains the position of the target device by calculating distances between the beacon devices and the target device using information about the reception time points of the wireless signals sensed by the respective beacon devices.

Abstract: A radio geolocation system is described in which a plurality of moving platforms such as aircraft concurrently receive a signal from a remote transmitter and the geolocation of the transmitter is determined. At each platform every thirty seconds a plurality of samples of the received signal are taken over a one second period. The samples are digitized and a time and GPS location stamp are added to each sample. The digitized samples with time and location stamps from all platforms are transmitted to a central location and stored in covariance matrices, one matrix per one second sample period. The signal samples in each matrix are processed utilizing a unique algorithm to generate a data set which defines a correlation surface. The data from a plurality of data sets are summed together on a point by point basis and normalized to yield a summation data set which defines a summation correlation surface.

Abstract: A system and method for locating a wireless device in one or more wireless networks within a selected geographic region. The method includes generating a computer model of a selected geographic region including a layout and inputting information associated with one or more components of a wireless network into the computer model. The one or more components includes at least one or more sniffer devices. Additionally, the method includes determining signal intensity characteristics of the one or more components of the wireless network over at least a portion of the selected geographic region and receiving one or more wireless signals from one or more wireless devices. Moreover, the method includes determining a plurality of probabilities associated with a plurality of locations for at least one of the one or more wireless devices.

Abstract: A method for determining the location of an actuating device is described. The method includes receiving transmissions from the actuator utilizing a plurality of multiple channel receiving devices, determining a direction to the actuator based on the signals received, and retrieving position, orientation, and time information for the plurality of multiple channel receiving devices relating to each transmission received from the actuator. Also included in the method is triangulating the position of the actuator based on the position, orientation, time, and determined direction to the actuator for the plurality of multiple channel receiving devices. Systems that perform the above method are also described.

Abstract: Groupings of receivers to be used for determining a target location by a multilateration system are selected to give the best Geometric Dilution of Precision result by eliminating that receiver that makes the greatest contribution. In this way the groups to be used may be selected as appropriate for the location of the target in real time avoiding the requirement to have a database holding the groupings to be used.

Abstract: A method of receiving a first set of target data points from a first data feed and receiving a second set of target data points from a second data feed arrangement. Comparing a time variable included in the target data points from the first set to the time variable included in the target data points from the second set to determine time matched target data points and further comparing a second variable included in the time matched target data points from the first set to the second variable included in the corresponding time matched target data points from the second set to determine fully matched target data points. Combining the first set of target data points with the second set of target data points when the fully matched target data points satisfies a predetermined threshold.

Abstract: To provide a positioning system, a positioning method, and a positioning server, which are capable of improving accuracy in detection of a position. In a positioning system, three or more access points connected to a terminal station by wireless communication are connected to a positioning server through a network, the access points transmit, to the positioning server, information regarding times of having received a signal transmitted from any one of the access points or the terminal station, and the positioning server measures a position of the terminal station based on the information regarding the times, the information having been received from the access points.

Abstract: The present invention improves WAMLAT Timing Availability by using timing from one or more of a variety of sources. These sources include unaugmented SATNAV timing, from GPS or/and GALILEO, GEO timing from pseudo SATNAV signals, additional GEO timing for non SATNAV applications, timing derived from both terrestrial and satellite television and radio transmissions, and stable on board oscillators to withstand short term interruptions in satellite timing. The use of one or more of these multiple sources of timing improves accuracy and reliability of wide area multilateration systems.

Abstract: Route planning methods for use by a package delivery service provider are disclosed that satisfy a stochastic daily demand while taking advantage of drivers' route familiarity over time. A model for estimating the value of driver familiarity is disclosed along with both an empirical and a mathematical model for estimating the value of route consistency, along with a Core Area Route Design which involves the concepts of combinational optimization, meta-heuristic algorithms, tabu search heuristics, network formulation modeling, and multi-stage graph modeling. In one embodiment, a service territory is divided into unassigned cells associated with a grid segment involving prior driver delivery stops, and a driver from a pool of unassigned drivers is assigned to a route based on examining each driver's grid segment visiting frequency limit with respect to a minimum limit so as to optimize driver selection based on of each driver's familiarity with the route.

Abstract: The invention described relates to a radio positioning system primarily for a mobile telephone network, in which a list of offsets in time, phase, frequency, or derivatives thereof, or their equivalents expressed as offsets in distance or derivatives thereof, of a plurality of transmission source signals, received at a given location, relative to a common reference are generated. Data is acquired from one or more receivers, the positions of which may be known or determined. Such data are offsets in time, phase, frequency, or derivatives thereof, respectively of signals received from the transmission sources relative to a reference source in each receiver or to each other. The acquired data is combined for calculating the list of offsets relative to the common reference.

Abstract: A system for enhancing the performance of a wireless communication device (WCD) while executing a direction of arrival (DoA) estimation. The performance may be improved through device management, and may include the collection of information from one or more sensors installed within the WCD. The sensor information may initially be used to determine an appropriate configuration for the device. Further, the sensor information may also be used to affect the behavior of the device while performing the DoA estimation.

Abstract: A system for tracking persons in a structure, using a mobile unit for transmitting a distinctive beacon signal to a wireless array network of RF transceivers when the signal is within a predetermined distance of one or more RF transceivers, and transmitting the received RF beacon signal and a signal representative of itself to other RF transceivers through the array to a computer gateway. The computer determines the location of the mobile unit from the transmitted signals and displays the location.

Abstract: A method of determining a location is provided. The method comprises placing a plurality of radio frequency (RF) tags within an area, mapping the placement of the plurality of RF tags within the area, detecting one or more of the plurality of RF tags in the area, and determining a location based in part on the mapping and on probability distributions associated with each of the one or more detected RF tags.

Abstract: There is provided a radio base station apparatus which is capable of increasing the probability of detection of a first path even if a radio transmission path fluctuates due to fading or the like, and of downsizing and reducing the cost of mobile radio terminal apparatus. SIR estimators 13-1 through 13-N calculate reception SIRs for respective subcarriers from output signals from pilot demodulators 12-1 through 12-N. SIR averager 14 averages the SIRs for the respective subcarriers to calculate an SIR for the overall signal. Based on the calculated SIR, threshold value setting unit 15 sets a threshold value for a path search. First path detector 19 conducts a path search based on the threshold set by threshold value setting unit 15. Arrival time calculator 21 calculates an arrival time based on a first path detected by first path detector 19.

Abstract: An apparatus for determining a position of a mobile wireless station comprises means for determining the position of the mobile wireless station in accordance with a position of a first reference wireless station, a position of a second reference wireless station, a first relative angular direction between the mobile wireless station and the first reference wireless station, and a second relative angular direction between the mobile wireless station and the second reference wireless station.

Abstract: A method for measuring the Time Of Arrival of signals in a communications network is provided. A transmitter emits a beacon that is a digital message of known content, followed by timing information. The message is preceded by a pseudo-random binary phase-shift keying (BPSK) modulated sequence that allows the receiver to synchronize on the received signal using the autocorrelation method. During the synchronization process, are computed the approximated Time Of Arrival (TOA) and approximated frequency difference between the local oscillator and the received signal. The content of the beacon message is then used for correcting the approximated TOA and the frequency differences, providing results of very high precision of TOA. The timing information that follows the beacon is used for network clock synchronization and for computing the distances between network nodes.

Abstract: The invention relates to a method of signal analysis that determines the location of a transmitter and to devices that implement the method. The method includes receiving by at least three receivers, from a transmitter, a first continuous-time signal having a first channel. The first channel includes a first plurality of signal carriers having known relative initial phases and having known frequencies which are periodically spaced and which are orthogonal to one another within a first frequency range. The signal analysis method also includes determining the phase shifts of the carriers of the first channel resulting from the distance the carriers traveled in reaching the first receiver. Analysis of the phase shifts yields time difference of arrival information amongst the receivers, which is further processed to determine the location of the transmitter.

Abstract: A managing wireless communication device assigns channels of a channel set to associated wireless communication devices. The associated wireless communication devices monitor the assigned channels for in-band signals including radar signals and report detections to the managing wireless communication device. The managing wireless communication device resets a timer associated with a channel when a report is received from one of the associated wireless communication devices. The timer may indicate how long the associated channel has been radar free.

Abstract: The present invention reduces the number of base stations required to carry out terminal position detection. A base station which serves for terminal position detection using radio signals comprises an antenna to transmit and receive a radio signal; a radio signal receiver which generates a received signal from the radio signal received; a signal processing unit which processes the received signal and generates a transmit signal; a radio signal transmitter which generates a radio signal from the transmit signal; a control unit which exerts control of the base station operation; and a signal processing unit for position detection which performs signal processing for terminal position detection. A signal receivable range with which a signal can be received by the radio signal receiver is made longer than a signal transmission range with which a signal is transmitted by the radio signal transmitter.

Abstract: The time difference of arrival for a signal received at two or more receiving sites as transmitted from a wireless communications device, is determined by a frequency domain technique. The constituent frequencies of the signals received at the two or more receiving sites are determined, including the phase, or a value representative of the phase, of each frequency component. The phase values for the same frequency are subtracted to yield a phase difference values as a function of frequency. The slope of the function represents the time difference of arrival for the wireless communications device signal as received at the two receiving sites. To determine the mobile location based on the determined time difference of arrival values, a seed or initial location is first assumed for the wireless communications device and the distance difference of arrival (the time difference of arrival multiplied by the speed of light) is calculated.

Abstract: The location of unmodified wireless assets in a wireless communication network may be identified using time differences of arrivals of a communication sequence at different network receivers. Time-stamping devices may include correlator circuits in parallel with signal decoders to time-stamp communication sequences. Cellular wireless networks may be frequency-multiplexed to increase spatial time-stamping density. Tags may be attached to passive assets to provide location identification information to network devices. Locations of assets broadcasting standard 802.11 radio frequency structures may be identified. Noise inherent in correlating a communication sequence may be reduced by using a selected correlation function.

Abstract: A detection system includes a sensitiveness level setup control section and a receiver control section. The sensitiveness level setup control section looks into a sensitiveness level setup file and finds the sequence of levels of sensitiveness to the received signals corresponding to the setup ID. The receiver control section converts, for each component, a sequence of levels of sensitiveness to received signals received from the sensitiveness level switching section into signals for designating levels of sensitiveness to received signals corresponding to the respective receivers, and transmits the signals for designating levels of sensitiveness to received signals through the communication network.

Abstract: Techniques for reducing the complexity and improving the accuracy of receive signal strength based location systems. The system comprises a plurality of radio sensor devices placed at known positions within a space in which devices are to be located. According to one technique, the path loss is measured between all combinations of pairs of radio sensor devices based on a test signal transmitted by each radio sensor device. A path loss model is evaluated to compute modeled path loss data between all combinations of pairs of radio sensor devices. For each measured path loss, a path loss error relative to each radio sensor device is computed by taking the difference between the measured path loss and the modeled path loss. The path loss error relative to each radio sensor device at any candidate position is interpolated from the computed path loss errors.

Abstract: A multistatic radar has a radar transmitter for illuminating a target with a radar signal. The target reflects the radar signal to three separate radar receivers, each performing a bistatic range measurement to the target. The three bistatic range measurements are combined in a quadratic equation having two solutions (roots). One solution (root) corresponds to a correct three dimensional target position with respect to the radar transmitter while the other is an incorrect three dimensional target position with respect to the radar transmitter. The incorrect three dimensional target position is identified and eliminated by comparing the three dimensional target position to the transmitter location, and the receiver locations. The incorrect three dimensional target position is also identified by the target altitude exceeding a threshold, typically set above 80,000 feet AGL.

Abstract: A radio frequency (RF) signal transmission device (the “device”) is used as a tracked target in a position tracking system (the “system”). In the preferred embodiments, the device's position is determined by analyzing the time difference of arrival of the device's RF signals received at multiple receivers which are part of the system. The device has two antennas spaced a known distance apart and the device alternately transmits on these antennas or can use code-division multiplexing for individual antenna's signal detection. The system detects the position of both antennas at their respective phase center and determines the distance between the two calculated antenna positions. By comparing the calculated distance to actual known distance the system can assess the quality of the calculated positions.

Abstract: Described herein is a system and method for detecting the position of a remote emitter (1) where the emitter (1) is emitting a radio frequency signal (2) in a radio field (3). The system and method uses at least one receiver (4) which is moveable within the environment of the radio field (3), each receiver (4) measuring and recording the amplitude of the radio frequency signal (2) and recording its precise location using a GNSS or GPS receiver. The data recorded is processed and compared to data predicted by the receiver(s) (4) to estimate a location of remote emitter (1).

Abstract: An apparatus for determining a position of a mobile wireless station comprises means for determining the position of the mobile wireless station in accordance with a position of a first reference wireless station, a position of a second reference wireless station, a first relative angular direction between the mobile wireless station and the first reference wireless station, and a second relative angular direction between the mobile wireless station and the second reference wireless station.

Abstract: Methods and systems for providing geographic specific services to receivers in a satellite communications network utilizes specific position location and information tagging to provide manual or automatic delivery of such services to the receivers.

Abstract: An intrusion detection system and method are provided that can utilize impulse radio technology to detect when an intruder has entered a protection zone. In addition, the intrusion detection system and method can utilize impulse radio technology to determine a location of the intruder within the protection zone and also track the movement of the intruder within the protection zone. Moreover, the intrusion detection system and method can utilize impulse radio technology to create a specially shaped protection zone before trying to detect when and where the intruder has penetrated and moved within the protection zone.

Abstract: A method of locating one or more reflectors in an environment crowded with reflectors. A transmitter and multiple receivers are used to obtain reflected signals. Each path of a reflected signal is defined by an ellipse having the transmitter at one focus and a receiver at the other. A reflector is assumed to lie on the ellipse, and an intersection of ellipses is assumed to be a reflector location. The region is iteratively divided into smaller and smaller cells, and a search algorithm is performed to determine whether a given point in each cell lies on an ellipse. A “solution” is a point that lies on the same number of ellipses as the number of receivers.

Abstract: Systems and methods for determining location by implication are described. A responsive environment includes a location determination method that operates in an area that is only partially instrumented with location-sensing devices. Some of the with location-sensing devices sense location ambiguously. For example, a location-sensing device may be deployed at a boundary between two target objects or areas of interest. The location of the target object, as reported by such devices, is considered ambiguous. While the object or person is known to be in a space, it is not clear which specific space. The location of ambiguously located objects can be disambiguated based on changes in the location of other objects. For example, if a document is placed on a shelf in an office, such action strongly implies that someone is in the office. Therefore, if a person is known to potentially be in the office or the outside hallway, the person's location is changed to be in the office.

Abstract: A method for use in a mobile communication system for estimating the location of a target mobile station (MS) which includes receiving signals from the target MS (N) at a plurality of receivers (MS1, MS2, MS3) in different locations and calculating the location of the target MS (N) from information obtained from the received signals, wherein at least one of the receivers (MS1) is a searching MS and wherein the calculation of location is carried out by the searching MS (MS1). The method may involve the target MS and the searching MS or MSs communicating by a direct mode of operation (DMO) link. The searching MSs may conveniently have GPS attachments. A mobile station which may be used as the target MS or as a searching MS and a system incorporating the same is also disclosed.

Abstract: The receiver (1) for radio-frequency signals (SV1, SV2, SV3, SV4), modulated by specific codes of transmitting sources, such as satellites (S1, S2, S3, 54), includes receiving and shaping means with frequency conversion for the radio-frequency signals for generating intermediate signals, a correlation stage formed of several correlation channels for receiving the intermediate signals and microprocessor means connected to the correlation stage in order to process the extracted data after correlation. Each channel includes a correlator in which the intermediate signals are correlated with at least two early and late replicas of the specific code of a visible transmitting source to be searched and tracked. The correlator further includes integrator counters for the correlated signals to provide a first amplitude value of the auto-correlation function of the early signals and a second amplitude value for the late signals.

Abstract: The time difference of arrival for a signal received at two or more receiving sites as transmitted from a wireless communications device, is determined by a frequency domain technique. The constituent frequencies of the signals received at the two or more receiving sites are determined, including the phase, or a value representative of the phase, of each frequency component. The phase values for the same frequency are subtracted to yield a phase difference values as a function of frequency. The slope of the function represents the time difference of arrival for the wireless communications device signal as received at the two receiving sites. To determine the mobile location based on the determined time difference of arrival values, a seed or initial location is first assumed for the wireless communications device and the distance difference of arrival (the time difference of arrival multiplied by the speed of light) is calculated.

Abstract: A position estimating method and apparatus are disclosed that determine an angle of arrival of a signal received from a terminal; determine a distance of the terminal, using an arrival time difference between the arrival time of the signal and a reference time; and determine a position of the terminal based on the determined angle of arrival and distance.

Abstract: A wireless terminal is designed to prevent the user from having to wait a long time in case fetching of search data takes a long time. The wireless terminal, if it determines the need of long time for the search of GPS satellites by a GPS transceiver, inhibits the GPS transceiver from searching GPS satellites and operates on a CDMA transceiver to search for CDMA base stations. The wireless terminal fetches only CDMA base station data pertinent to the CDMA base stations and sends to a position data server, and the position data server points the location of the wireless terminal based solely on the CDMA base station data provided by the wireless terminal. Based on the inhibition of search of GPS satellites by the GPS transceiver, the time needed until the reception of positioning result can be reduced, and the user is prevented from being subjected to long time waiting.

Abstract: A system and method for synchronizing internal clocks of receiving stations of a locating system are described. A beacon transmits reference data packets at a known position. A first arrival time is compared to a second arrival time to determine a correlated arrival time data. The first arrival time is a time of reception of the reference data packets by a first receiving station, and the second arrival time is a time of reception of the reference data packets by a second receiving station. A linear polynomial fit is computed as a function of the correlated arrival time data and the first and second arrival times. Times of arrival of data packets at the first and second receiving stations is synchronized as a function of the linear polynomial fit.

Abstract: The location of unmodified wireless assets in a wireless communication network may be identified using time differences of arrivals of a communication sequence at different network receivers. Time-stamping devices may include correlator circuits in parallel with signal decoders to time-stamp communication sequences. Cellular wireless networks may be frequency-multiplexed to increase spatial time-stamping density. Tags may be attached to passive assets to provide location identification information to network devices. Locations of assets broadcasting standard 802.11 radio frequency structures may be identified. Noise inherent in correlating a communication sequence may be reduced by using a selected correlation function.

Abstract: A method for configuring a local positioning system comprises orienting a survey antenna coextensively with a primary beacon associated with a work area. A transmitter or transceiver transmits a first transmission signal from the survey antenna. A receiver or transceiver receives the first transmission at one or more secondary beacons associated with the work area. A data processor determines first elapsed times from the transmission time of the first transmission signal to at least the arrival time at respective corresponding secondary beacons. Each of the first elapsed times falls within a filtering time window, or satisfies an edge timing criteria of the coded signal, or both to reduce multi-path error. The first elapsed times are converted into a first position in at least two spatial dimensions for the primary beacon.

Abstract: A process for measuring the location of people and objects carrying radio frequency (RF) transmitters (TXs) that transmit messages to a plurality of RF receivers (RXs) located in a space. Each RX is in communication with a computer of a computer network and forwards data received from the TXs to the network via its associated computer, along with a value indicating the signal strength of the received TX transmission. The signal strengths attributable to the same transmission are used to form a locating signal strength vector which is then compared to exemplary vectors generated from signal strength readings gathered in a calibration procedure from a set of representative locations in the space. In comparing the locating vector to the exemplary vectors, constraints are enforced on movements between locations (e.g., cannot pass through walls) and to probabilistically enforce expectations on transitions between locations.

Abstract: Signals received from mobile station by respective slave units each are attenuated by a combination of attenuation factors set for the respective slave units, the attenuated signals thereafter are combined into a resultant signal in master unit, and the combination of attenuation factors is changed based on a predetermined rule. Then information about magnitudes of powers of signals received from the mobile station by the respective slave units is acquired based on change of information about a power of the resultant signal occurring with change in the combination of attenuation factors. At this time, the signal received from the mobile station by each slave unit increases its power with decreasing distance of the slave unit to the mobile station; therefore, distances from the mobile station to the respective slave units are estimated based on the information about the magnitudes of the powers, and the location of the mobile station is suitably estimated thereby.

Abstract: The present invention is directed to a system and method for Doppler track correlation for debris tracking in PCL radar applications. The disclosed embodiments describe the systems and methods used in the detection of debris pieces and the association of the Doppler signals from the debris pieces across multiple illumination channels. The present invention also provides computation of debris state vectors and the projection of trajectories to determine debris impact points.

Abstract: This invention relates to a method and system for the radio location of CDMA and non-CDMA enabled transmitters within a reception zone. The invention exploits the superposition of antenna patterns that create complex and asymmetrical interference structures at very small scales. By randomly distributing a random antenna array of M elements across a two or three-dimensional surface, fine scale interference structures on the scale of ¼ the carrier wavelength are generated. Once the minimum number of antennas are placed, additional antennas will not improve the resolution. Such interference structures when sampled at ? the carrier wavelength or greater yields unique spatial patterns with respect to a given antenna array geometry and transmitter location. The invention incorporates signature recognition (matching) and orthogonal sub-space projection estimators to derive location estimates of a radio transmitter.

Abstract: Wireless devices within an ad-hoc wireless network adaptively set their transmission power levels based on locally available information. Initially, each such wireless device sets its transmission power level to a relatively low level, and gradually increases its power level up to a predetermined maximum transmission power level. As the transmission power increases, the wireless device is able to incrementally connect with additional wireless devices located at increasing distances from the wireless device. As the wireless device connects with these additional wireless devices, it checks a connectivity constraint. When the connectivity constraint is satisfied, the wireless device stops increasing its power and operates at its current power level. In one embodiment, the connectivity constraint is a geometric connectivity constraint based on the angular distribution of wireless device connections.

Abstract: A system and method for rapidly determining the source of an incoming projectile applies controlled, active RF energy source(s) to illuminate a target area/projectile, and exploits Doppler induced frequency shifts from multiple receivers to develop a vector solution. The preferred solution applies continuous wave (CW) RF illuminators to flood a local region with a controlled source of radio frequency energy and one or more displaced receiver elements. The system operates multi-statically and as an incoming projectile enters the illuminated region, reflected energy from one or more illuminators is detected by one or more displaced RF receivers. Doppler shifts imparted on the reflected signals are detected by the receivers as the projectile moves through the region. Appropriate processing of the receiver outputs generates Doppler time-frequency profiles that are used to derive an estimate of the projectile flight vector in 3-space (x,y,z).

Abstract: A portable terminal carried by a user and in wireless communication with a local area network for displaying data based on the physical location of the user. A plurality of network nodes is distributed throughout a venue, such as a shopping mall or a store, in which products are offered for sale. The location of the user is determined by the location of the access node in communication with the terminal. The data may include a recommendation to purchase the product.

Abstract: A method for automatically changing the address and telephone number of an occupant when the occupant moves from one internal address to another internal address. The foregoing is accomplished by placing a radio frequency identification tag in occupant's nameplate, wherein the tag contains encoding information that identifies the occupant so that when the occupant changes his/her location, the nameplate may be used to update a data base and determine the occupant's new address and telephone number.

Abstract: System and methods are disclosed for passively determining the location of a moveable transmitter utilizing a pair of phase shifts at a receiver for extracting a direction vector from a receiver to the transmitter. In a preferred embodiment, a phase difference between the transmitter and receiver is extracted utilizing a noncoherent demodulator in the receiver. The receiver includes antenna array with three antenna elements, which preferably are patch antenna elements aced apart by one-half wavelength. Three receiver channels are preferably utilized for simultaneously processing the received signal from each of the three antenna elements. Multipath transmission paths for each of the three receiver channels are indexed so that comparisons of the same multipath component are made for each of the three receiver channels. The phase difference for each received signal is determined by comparing only the magnitudes of received and stored modulation signals to determine a winning modulation symbol.