Abstract: A radar system and method for detecting and tracking a target of interest in the presence of interference, wherein the interference emits interfering signals, includes a receiver for receiving the interfering signals directly from the interference. The receiver also receives reflected signals, wherein the reflected signals is the interfering signals reflected by the target of interest. The interfering signals and the reflected signals are compared to detect the target of interest. In one embodiment, the reflected signals and the interfering are cross-correlated. The results of the cross-correlation are used to obtain range, position, and velocity information about the target of interest from a range/Doppler map.

Abstract: A method for calculating the range to a moving object by way of a sensor that determines the angle of the object. The sensor and the object move relative to one another, and after one measurement the procedure is as follows: on the assumption that the target maintains a constant velocity, a number of possible target ranges are calculated, as well as areas of uncertainty associated with these ranges, so-called “straight trajectory models” (410, 411, 412), on the assumption that the target accelerates, a number of possible target ranges are calculated, as well as areas of uncertainty associated with these ranges, so-called “maneuvering models” (420, 421, 422), a number of the straight trajectory models (410, 411, 412) having a maneuvering model assigned to them.

Abstract: In a radar system, sampled aperture data are received from an antenna array. The sampled aperture data include data that do not correspond to echo returns from a beam transmitted by the antenna. A covariance matrix is generating using the sampled aperture data. An eigenvalue decomposition is performed on the covariance matrix. A direction of arrival is determined from which at least one jammer is transmitting a signal included in the sampled aperture data, based on the eigenvalue decomposition.

Abstract: Disclosed are an apparatus for forward beamforming using a terminal feedback and a method thereof. The base station estimates an angle of arrival (AOA) range of a user signal from reverse link received data and calculates a plurality of beamforming weights steering the estimated AOA range. Then, the base station transmits a user pilot signal by sequentially using the plurality of beamforming weights at different time areas through a control channel to estimate a forward channel conditions. A terminal calculates the user pilot signal power for all fingers at the respective time areas and feeds a time area number corresponding to the greatest power back to the base station. The base station transmits a data channel signal using a beamforming weight corresponding to the time area number fed back from the terminal.

Abstract: A beacon modulated by a pattern is authenticated by recording an array of light intensities for each point in a field of view; digitizing the array of light intensities; modifying a first array according to the digitized light-intensities and the modulation pattern; repeating these steps for additional frames at the current viewpoint; if the beacon is found then repeating these steps for additional frames; if the beacon is found and additional frames were processed then authenticating the beacon at the point in the current viewpoint corresponding to the value in the first array that exceeds a first threshold by the widest margin; if the beacon was not found, moving to a new point in the field of view and repeating the steps above; if the beacon is again not found, adjusting the modulation bit pattern x bits, and reprocessing the viewpoints in the field of view using the steps above.

Abstract: A method for estimating a time delay including the steps of first, estimating a channel spectrum from a received signal and a known reference signal, second, extracting a virtual array structure from the estimated channel spectrum, and third, determining the signal time delay using the virtual array structure. Further, a system for estimating a time delay including a channel spectrum estimator, means for extracting a virtual array structure and means for determining the time delay is provided. The channel spectrum estimator is used for estimating a channel spectrum from a received signal and a known reference signal. The means for extracting a virtual array structure uses the estimated channel spectrum. The means for determining the time delay uses the virtual array structure.

Abstract: Spatial profile creation section 102 creates an intensity distribution, that is, a spatial profile or spatial information of reception signals with respect to the directions of arrival of signals using reception signals prior to despreading received via antenna elements 101-1 to 101-4. Direction of arrival estimation section 103 estimates the directions of arrival of signals sent from other parties of communication from the spatial information created by spatial profile creation section 102 and divides and outputs the information of the directions of arrival to reception units 104-1 to 104-4 according to the direction of arrival. Beam formers 111 in reception units 104-1 to 104-4 each rotate the phase of the output reception signals from antenna elements 101-1 to 101-4 at predetermined angles based on the information of directions of arrival and combines these rotated reception signals so as to increase the reception levels of the signals sent from the directions of arrival.

Abstract: A radio direction finding system for a low signal quality transmission signal performs a Fast Fourier Transform (FFT) on an entire received RF band into a number of FFT bins, each serving as an IF filter. The contents of each FFT bin are demodulated to decode a frequency signature from the encoded RF signal. A signal-to-noise ratio comparator receives the FFT baseband samples and determines the signal level from the known frequency signature. The FFT baseband buffer with the greatest SNR corresponding to a particular FFT frequency bin is outputted as a direction finding metric.

Abstract: A method and apparatus for tracking a target. A signal from the target is received using a directional antenna and is digitized to provide a time series of samples. The samples are transformed, preferably by a wavelet transform. A signature of the target is identified in some of the transformed samples and a direction to the target is determined from others of the transformed samples. Target identification and target direction determination are iterated, with the identification being based on the most recently determined direction, and with the direction determination being based on the most recent identification, until a termination criterion is satisfied. Using wavelet transforms gives the antenna an effective beamwidth twenty percent narrower than the antenna aperture.

Abstract: A switch modulated low duty cycle low energy mass limited radio frequency beacon system for locating spent, un-exploded or experimental munitions projectiles in a large open-air test range or within a dirt backstop. The disclosed locator beacon is mounted on a rear portion of a projectile before launch and includes a protective (and antenna length-shortening) resin dielectric material housing in which locator beacon circuit components are contained and immunized against high G forces by a combination of component supporting, energy deflecting and energy absorbing protective arrangements.

Abstract: A radio-wave arrival-direction apparatus calculates a correlation matrix of received signals by correlation calculation between antenna elements, and calculates a noise spatial eigenmatrix, of which each row or column is an eigenvector belonging to a noise eigen-space, by eigenvalue factorization of the correlation matrix. The apparatus also factorizes a matrix including a product of the noise spatial eigenmatrix and a conjugated and transposed matrix of it to an upper or lower triangular matrix, using cholesky factorization. The apparatus calculates an angle evaluation value in a predetermined angle range of an arrival-angle evaluation function using the derived upper or lower triangular matrix, and determines an arrival angle based on the calculation result. A calculation amount in a variable angle range can be thus reduced without causing accuracy degradation of arrival direction, in an algorism requiring an angle sweep for arrival angle estimation of MUSIC method or the like.

Abstract: A direction finder apparatus and method are provided. The direction finder apparatus includes an antenna system, a RF front end, and an analog signal detector that detects an electromagnetic signal and provides in response a characteristic signal without an underlying carrier wave. The direction finder apparatus further includes an analog-to-digital (A/D) converter, a fast Fourier transform (FFT) processor that produces a plurality of component frequency approximations representing frequency components of the AM signal, a plurality of storage bins, and a post-processor. The post-processor determines a maximum S/N ratio from among the plurality of component frequency approximations. A direction of arrival (DOA) angle of the RF signal is determined when the antenna system is oriented to produce a maximum S/N ratio.

Abstract: A wireless tracking system consists of a wireless target including a wireless communication system for transmitting a data packet over a communication path, and a locating station for determining a position of the target. The data packet transmitted from the target includes an identification code uniquely associated with the target. The locating station includes a configurable directional antenna, a communication interval processing system, a direction processing system, and a position processing system. The communication interval processing system is in communication with the directional antenna and determines the transmission interval of the transmitted data packet over the communication path. The direction processing system determines the transmission angle of the communication path, and is in communication with the directional antenna for controlling the configuration of the directional antenna so as to facilitate the determination of the transmission angle.

Abstract: The invention provides a method and apparatus for determining the direction of a signal such as for example a received radio signal in a cellular mobile communication system. At lest two antenna arrays (10, 12) are connected to associated processors (14, 16) for extracting the desired signal and two independent direction of arrival estimates are determined in associated direction estimators (18, 20). A similarity testing unit (22) determines the direction of arrival and the accuracy of this estimate from the difference between the two estimates. A feature of the invention is controlling the beam form of a downlink signal in response to the direction estimate and the determined accuracy.

Abstract: A direction finder apparatus and method are provided. The direction finder apparatus includes an antenna system, a RF front end, and an analog signal detector that detects an electromagnetic signal and provides in response a characteristic signal without an underlying carrier wave. The direction finder apparatus further includes an analog-to-digital (A/D) converter, a fast Fourier transform (FFT) processor that produces a plurality of component frequency approximations representing frequency components of the AM signal, a plurality of storage bins, and a post-processor. The post-processor determines a maximum S/N ratio from among the plurality of component frequency approximations. A direction of arrival (DOA) angle of the RF signal is determined when the antenna system is oriented to produce a maximum S/N ratio.

Abstract: The angle at which a multipath finger produced by a digital radio communication source arrives at an antenna array can be estimated using an uplink weight vector associated with the multipath finger. Due a characteristic of uplink weight vectors used in antenna arrays having a shift invariance structure, the estimate of the angle can be calculated based on the uplink weight vector.

Abstract: A method and a system are disclosed which utilize the polarization properties of electromagnetic fields for a determination of the direction to the source of the electromagnetic radiation. The method and system primarily use a particular antenna device with is associated receiver means for obtaining a wave field measurement Assuming separate frequencies, the present method and system also make it possible to distinguish between several sources and register their separate polarizations simultaneously. At least three electric antennas, or three magnetic antennas, are used to measure the wave field. The registered field components need not be orthogonal to each other. The measured wave field is processed in accordance to predetermined formulae so that the propagation direction and other polarization characteristics, such as the spectral intensity I and the spectral degree of circular polarization rc, are derived. Furthermore the measurements need not be from more than one point in space.

Abstract: A pulse Low Probability of Intercept (LPI) signal discriminator has a soft-limiting IF amplifier chain for receiving an IF signal to soft-limit any high-peak IF signals in the IF signal and a high-peak amplitude compressive circuit followed by an integrator which integrates the signal over a predetermined time to produce a high output when a LPI signal is present. The integrator is connected to a threshold detector which outputs a trigger signal when a high output from the integrator is received. In a receiver having a plurality of channels for received signals from a number of antenna, one channel for each antenna, the received signals are down converted to IF signals and applied to analog-to-digital converters (ADCs) which are connected to a digital processor.

Abstract: A system and method for determining the position of an aircraft. An aircraft signal is received by a first antenna and a second antenna, the first antenna being at a known baseline distance from the second antenna. A processor is used to calculate the time difference of arrival range between the second antenna and the aircraft using a common time reference signal. The position of the aircraft is determined by a position determinator based upon the baseline distance between the first and second antennas, the range between the first antenna and the aircraft, and the time difference of arrival range between the second antenna and the aircraft.

Abstract: A direction of arrival (DOA) estimation apparatus of the present invention comprises a plurality of A/D converters that converts a plurality of complex base band signal obtained from the receiving signals of a plurality of antenna elements to respective complex digital signals, a plurality of low pass filters that outputs complex low pass signals with attenuated high frequency components of respective complex digital signals, a plurality of down samplers that outputs complex down sampled and multiplied signals by down sampling the complex low pass signals and multiplying by integral number of sampling intervals of respective A/D converters, and a data transfer section that stores respective complex down sampled signal thus obtained from respective antenna elements temporary and then transfers the data. A variable directional signal receiving and transmitting apparatus of the present invention performs an antenna directivity control based on the output data from the above data transfer section.

Abstract: The direction-of arrival estimation by means of a subspace-based algorithm such as MUSIC or ESPRIT is formed by using reduced-bandwidth signals as compared with communication signal waves. The narrower-bandwidth signals is obtained by each mobile telephone transmitting a modulated version of a lower-transmission rate test signal as well as a communication signal wave or by band-pass filtering the received communication signal waves in a base station. A direction-of-arrival estimation is formed by using a reduced number of signals for the direction-of arrival estimation. The number of direction-of-arrival estimating signals is reduced by discarding a part of the received signals, by multiplexing the received signals by the sub-array and forming a direction-of arrival estimation for each sub-array, or by using an additional array antenna having a reduced number of elements.

Abstract: Array elements 111-1 to 111-n of array antenna 101 are arranged at respective different heights from a ground so as not to overlap to each other in a vertical direction. Received frequency conversion section 102 converts a radio frequency signal received at each of the array elements 111-1 to 111-n of array antenna 101 into an intermediate frequency signal or baseband signal. A/D conversion section 103 converts an analog signal output from received frequency conversion section 102 into a digital signal using a proper sampling frequency. Direction estimating section 105 estimates directions of an arrival radio signal in a horizontal plane and vertical plane using received digital signals obtained in A/D conversion section 103. It is thereby possible to suppress increases in the number of array elements and computation amount, and to improve estimation accuracy in the vertical direction and resolution at the time a plurality of signals arrive.

Abstract: The directional antenna apparatus of a base station, after sensing the direction of an undesired wave, calculates the optimum amplitude weighting coefficients and optimum phase weighting coefficients for a plurality of directions between the move starting point and move end point of a mobile station and creates a reference table. Then, when receiving a request for communication from the mobile station, the directional antenna apparatus reads weighting coefficients from the reference table, sets them in each antenna element, and points the directivity toward the mobile station, and starts communication. Then, calculating the time when the mobile station arrives at the position corresponding to each direction from the destination of the mobile station and its moving speed, and reads one by one the optimum amplitude and phase weighting coefficients from the reference table, and sets them in each antenna element, and communicates with the mobile station, while tracking the mobile station.

Abstract: A system for calculating the bearing of a signal source, with a directional antenna, provides corrections for distortion, such as due to a small fuselage of the monitoring aircraft and the elevation angle of an intruder aircraft with respect to the monitoring aircraft. A correction is applied to the bearing estimate that is based on relevant factors, such as the fuselage size and the elevation angle of the intruder aircraft. The correction can be calculated or applied through the use of a look-up table, which may be either pre-selected or selected after calculation of the elevation angle of the intruder aircraft.

Abstract: A transmitting-receiving station for use in radio wave diversity comprises two antennas (21, 31), a distributor-composer (30), and a transceiver (40), and tarder comprises a phase prefixed-adjuster (22), a level prefixed-adjuster (23), and a delayed prefixed-adjuster (24) as one of prefixed adjusters supplied between the antenna (21) and the distributor-composer (30). The two antennas have a predetermined distance therebetween for use of space-diversity. The distributor-composer connects to the two antennas on one side and a transceiver on the other side, distributes a signal to be transmitted from the transceiver, and composes two signals to be received from the two antennas. The prefixed adjuster manually adjusts and fixes each two values of phases, levels, and delay times of the signals dependent of the two antennas respectively so as to be made the same value each other on a connecting point of the distributor-composer.

Abstract: The present invention relates to multi-function, multi-channel digital receiver architecture for performing three distinct receiver functions including simultaneous intrapulse analysis, direction finding and LPI signal detection; for determining parameters of incoming signals, comprising a plurality of receiver channels, each channel including a respective antenna for receiving the signal; a down-converter for converting the signal to an intermediate frequency (IF) signal; and an analog-to-digital converter operatively coupled to receive the IF signal and to provide a digital signal at a sampling rate, the digital signal being indicative of the amplitude and phase of the received signal in the channel, and a digital processor operatively coupled to receiving the digital signals from each of the plurality of channels for determining the amplitude and phase intrapulse profiles; by combining the amplitude and phase intrapulse profiles from all of the plurality of channels to provide both intrapulse and conventio

Abstract: An object of the present invention is to provide a selective level measuring apparatus with wider dynamic range of effective value detection, compared with the range by a conventional one. The apparatus according to the present invention comprises a gain control means arranged before an effective value detection section for varying a gain by a control voltage, so that a signal level inputted into the effective value detection section may be kept to be constant level by the gain control means, and the signal level of the signal to be measured is measured and indicated through the control voltage. Performing such operations allows the selective level measuring apparatus for the effective value detection to secure a dynamic range defined by a variable quantity of the gain control means. Accordingly, the present invention provides the wider dynamic range of the effective value detection comparing with that by the conventional one.

Abstract: A system for determining the direction that an object is pointing is disclosed. The pointing direction is calculated by determining phase differences between signals arriving at different positions on the object from a single source. Preferably the signals are received from Global Positioning System satellites and multiple antennae are positioned appropriately on the object. A number of methods are disclosed to obtain both the integer and fractional parts of the phase difference. Once the absolute value of the phase difference is determined and the satellite positions are known, it is possible to determine the direction that the object is pointing. A number of possible applications are disclosed including aerial imaging, artillery weapons aiming and satellite receive dish alignment.

Abstract: A direction finder is provided that can measure the incoming angles of plural incoming signals without spatially moving antenna elements and can be used in outdoor mobile communication environments. The direction finder also can shorten the measurement time. An array antenna comprises plural antenna elements arranged at regular intervals. The received signal components due to the mutual coupling between the antenna elements are removed by multiplying time series signal groups by the inverse matrix of a coupling coefficient matrix of the array antenna. The time series signal groups are obtained by modulating signals received with the array antenna. The covariance matrix of the received signal group can be subjected to a movement averaging process in terms of the Vandermonde format.

Abstract: A radar apparatus comprising: a receiving antenna having an array antenna in which a plurality of antenna elements are arrayed in a horizontal direction; and a signal processing section for carrying out recognition of a target existing in a predetermined horizontal bearing range from receive signals received by the receiving antenna, by electrically carrying out horizontal scanning of an antenna pattern of the receiving antenna, wherein at least one of the antenna elements is placed with a shift in a vertical direction, and wherein the signal processing section detects an altitudinal bearing of the target by a monopulse method by use of a receive signal from the antenna element with the shift in the vertical direction.

Abstract: A process and device related to multisensor radio direction finding receivers usable in radio communication systems including several emission sources. The process and device isolate the contribution of each emission source in sensor signals so as to perform direction finding on a single emission source only, based on learning sequences inserted into waveforms emitted by each of the emission sources. Such a process and device may find particular application to cellular communication networks.

Abstract: An array antenna for direction-finding includes antenna elements which define a triangular outline well-suited for meeting space constraints or reducing reflections from mounting conditions associated with the array antenna. The actual geometric configuration of the antenna elements is limited to certain triangular configurations with corresponding geometric correction factors to maintain the accuracy of estimating the angle of arrival. A processing system determines the appropriate angle of arrival based upon differential phases received in the antenna elements and the appropriate geometric correction factor.

Abstract: Signals in the form of wave elements of one or more subscriber signals are received at a receiving device assigned a number Ka of receiving sensors and the direction of the signals is estimated. Ka received signals are received via the receiving sensors and are composed of at least one subscriber signal which has a transmitter-specific fine structure impressed on it. A kth subscriber signal, with k=1 . . . K, is transmitted by means of Kd wave elements whose directions of arrival at the receiving location differ. Channel impulse responses assigned to the Ka receiving sensors are determined from the received signals, and the direction of arrival of at least one wave element is determined from the channel impulse responses. The direction estimation can advantageously be used in mobile radio, radar, sonar or seismic measurement systems.

Abstract: A system and method for finding the direction of a wave source using an array of sensors. The system includes a sensor array for measuring waves from the wave source, an approximate-direction finder for finding the approximate direction of the wave source in terms of a sensor pair from the sensors, a precise-direction finder for finding the precise direction of the wave source based on the approximate direction found, and a measurement qualification unit for evaluating the validity of the precise direction under a measurement criterion and discarding the measurements if the criterion is not met.

Abstract: An integrated receiver includes an Instantaneous Frequency Measurement (IFM) device, an interferometer and switches. The IFM receives signals from a target and determines the frequency of the signals. The IFM includes the shared N-channel phase receiver. The interferometer also receives the signals from the target and determines the angle-of-arrival (AOA) of the signals. The interferometer includes the shared N-channel phase receiver and shares the shared N-channel phase receiver with the IFM. The switches selectively connect the shared N-channel phase receiver to the IFM when the IFM is determining the frequency of the signals, and selectively connect the shared N-channel phase receiver to the interferometer when the interferometer is determining the AOA of the signals. The shared N-channel phase receiver determines phase information indicative of the frequency of the signals and the AOA of the signals.

Abstract: An algorithmic technique which allows antenna arrays that are used for interferometric direction finding to have elements with arbitrary orientation. This technique allows the phase errors associated with non-identical element orientation to be estimated, without explicit knowledge of either the polarimetrics of the array elements or the polarimetrics of the source. It relies upon the fact that there exists a single number which describes the polarimetric interaction, and that this number can be estimated and then utilized to remove the phase component due to polarimetric interaction. This technique makes it feasible to incorporate direction finding arrays into articles that could benefit from such arrays, but because of size or shape constraints, were previously not able to do so.

Abstract: In a navigation device for a motor vehicle in which a standby operation is provided with limited power consumption, the standby operation is maintained for a period of time after the vehicle ignition and/or the navigation device is switched off, the period of time depending on the previous operating state of the navigation device. The navigation device is switched off afterwards.

Abstract: A directional finding system for providing a corrected compass bearing based upon true north rather than magnetic north for a selected location. The true bearing is calculated by determining a present position with a GPS receiver or other location finding device, then selecting the deviation between true north and magnetic north for the present position from a store of magnetic deviation data, and finally correcting the magnetic bearing by the deviation to find a true bearing. The store of magnetic deviation data comprises the deviation between true north and magnetic north for any location. Additionally, the true bearing can be further corrected by a time-based magnetic deviation based upon the monotonic movement of the magnetic north pole. The true bearing is presented on a display along with the magnetic bearing and the present position.

Abstract: A near-field calibration arrangement for an antenna array determines the phase shifts or attenuation of the elemental control elements of the array. The calibration system includes a probe located in the near field, and a calibration tone generator. The tone generator is coupled to the probe in the case of calibration of a receive antenna, and to the signal port of the array in the case of calibration of a transmit antenna. A code generator generates sets of values, with each set being orthogonal to the others. The codes are applied to the control input port of the array antenna, so that the codes encode the tone passing through the antenna. The encoded tones are applied to a decoder and processor, which processes the signals to determine the phase shift or attenuation associated with each bit of the control signal. A transmit antenna attitude determination or pointing arrangement uses the calibration tone generator in conjunction with a plurality of remote sites.

Abstract: A sensor performs input pulse deinterleaving based on an angle of arrival (AOA) of each sensed pulse. An AOA determination unit determines an AOA for each received pulse. The pulses are then sorted based on AOA into a number of AOA bins. The data within each bin is then analyzed to determine whether it corresponds to an emitter of interest. Bin data corresponding to emitters of interest are then transmitted to a remote processing facility for additional processing.

Abstract: An efficient monopulse direction finding technique is based on the best algorithm in the least squares sense for a given antenna configuration. The algorithm simultaneously uses complex voltage data from all of the antenna ports, i.e., all of the available data received. No a priori emitter polarization information is assumed. Only a two dimensional search for the performance index minimum is needed to find the solution. The method is extended to N emitters with a search in only 2N space for the N emitter angles.

Abstract: A method is provided for the direction of arrival (DOA) tracking of at least one source, along a single azimuth axis or along both azimuth and elevation axes. The method includes the steps of selecting all the high peaks from a DOA function as potential track points, converting the potential track points into a plurality of tracks and selecting a true track from the plurality of tracks.

Abstract: A method and apparatus for determining from a moving observer the location, in terms of latitude, longitude, altitude, and velocity, of a stationary or moving radar emitting a pulsed or continuous-wave signal. The moving observer extracts from the radar signal significant electronic support measures (ESM) parameters, including frequency, pulse repetition interval, and pulse width, and determines from those parameters whether a radio frequency (RF) or pulse repetition frequency (PRF) measurement technique is appropriate, and whether the radar signal angle-of-arrival (AOA) must be computed. The emitter location is computed using a ratio of sequential frequency measurements, and the moving observer continues to collect frequency measurements until the location of the emitter can be established to within a predetermined degree of certainty.

Abstract: A system and method which enables a user platform to perform low level control of a channel unit which performs acquisition and tracking of Global Positioning System (GPS) signals processing the measurement platform which includes the channel and that performs all satellite tracking functions which are driven by interrupts. Intermediate measurements data generated therefrom, for example code phase, carrier phase and Doppler, are communicated to a user platform which computes receiver position and time. As a result, the user platform can easily be configured to perform user-specific processes without incurring conflicts with the interrupt driven processes occurring on the measurement platform. Furthermore, the user platform is configured to issue commands to the channel unit to control the operation of the measurement platform. Thus, the performance of the measurement platform can be tailored specifically to the end user application.

Abstract: A personal direction finding apparatus for determining the direction to be followed in order to reach a predetermined spot which includes a headset provided with two earphones and a circuit for generating a track error signal. The circuit includes a compass supported on the headset for outputting a heading signal corresponding to the heading of the direction of travel, a receiver for a position location and navigation system outputting a signal for the heading to be followed via one output, and a track error computing circuit.

Abstract: A method and apparatus reduces the ambiguities in the determination of cellular telephone locations in a location finding system based on the use of multipath signals. A location finding base station determines a signal signature from a subspace of an array covariance matrix. The signature is compared to a database of calibrated signal signatures and corresponding locations, and a set of likely locations whose calibrated signatures best match the measured signature is selected. A subset of most likely locations is selected from among the likely locations by comparing a function which represents how closely the measured signature matches the set of calibrated signatures with functions which represent how closely each likely signature matches the set of calibrated signatures. The locations corresponding to the best matching function are selected.

Abstract: A method for traffic monitoring, particularly at airports, is disclosed including the localization of a traffic object is carried out by direction finding and by additional information. The radio communication between the traffic object and a control center is recorded and fed to a speech recognition unit on the side of the control center; an identification phrase transmitted together with the message of the traffic object is identified in the speech recognition unit on the side of the control center and allocated to the localized traffic object; and that the allocated identification of the localized traffic object is continuously maintained, the source of the identification being on the side of the traffic object.

Abstract: System for determining the position of radar transmitters where the system includes at least one information center with associated cells and means of communication between the information center and the cells with a restricted transfer rate utilising existing infrastructure in the country, such as for example a national telephone network and also mobile telephone networks and their base stations. Each cell includes at least one sensor in order to be able to detect radar signals. Leading edges of pulses in the radar signals are detected and time-marked after which they are sorted according to PRI (Pulse Repetition Interval). The time of arrival for the first pulse in a pulse train is calculated and data reduced by modulo calculation to a value that as a maximum is the propagation time difference for pulses between two cells in a pair of cells/sensors that are used together for calculating the bearing.

Abstract: A helical antenna having stubs spaced along the helix curve length and extending toward the central axis of the helix, such that the performance characteristics of the antenna, such as gain and circular polarization, are maintained while the size of the antenna--diameter and length--are reduced.

Abstract: A spread spectrum signal detection system comprising two spatially separated receivers, a correlator, such as a time integrating correlator employing acousto-optic cells, which is connected to the outputs from the two receivers to produce a signal representative of the cross correlation function of the two spread spectrum signals, a filter arranged to transmit only the central portion of the cross correlation function and a signal processor to produce the cross spectral density and thereby determine the presence of the spread spectrum signal. The direction of arrival of the spread spectrum signal can be determined by measurement of the angle of the phase slope of the cross spectral density. The acousto-optic cells can be Bragg cells.