Abstract: System and method for resolving phase ambiguities of various transducer arrays, including non-coplanar interferometer antennas on an aircraft skin, in order to determine the direction of arrival of a signal received by the array and emitted by a source remote from the array.

Abstract: The present invention relates to estimating the Angle of Arrival (AoA) of a signal from a user equipment received at a base station of a wireless telecommunications network where the base station has a multi-beam antenna. A signal received from a user equipment is received by the each of the multiple beams of the antenna, and the two adjacent beams receiving the highest amplitude from the end user are selected. A ratio of functions of the amplitudes of the two selected beams, such as a ratio of the difference between the amplitudes of the two beams to the sum of the amplitudes is calculated and compared to a data store of ratios. The data store stores expected ratios corresponding to AoAs and the calculated ratio is compared to the pre-calculated expected ratios to extract an estimate of the AoA of the signal from the user equipment.

Abstract: A radar system with a radar sensor (10) which comprises a transmitting module (20), a receiving module (22) and a supply network (64), wherein the transmitting module (20) comprises a first plurality of partial antennas (26, 28, 30, 32, 34) and the receiving module (22) comprises a second plurality of partial antennas (46, 48, 50), and wherein the supply network (64) operates at least one partial antenna (30) of the transmitting module (20) together with at least one partial antenna (48) of the receiving module (22) in a first operating mode, to obtain a first, low angular resolution, and wherein the supply network operates one group of partial antennas (26, 28, 30, 32, 34) of the transmitting module (20) together with a group of partial antennas (46, 48, 50) of the receiving module (22) in a second operating mode to obtain a second high angular resolution.

Abstract: Coverage areas for wireless networks are divided into a plurality of cells that are arranged in rows. Channel frequencies are assigned to cell sectors and associated with respective antenna axes. The antenna axes of adjacent rows are alternatingly rotated, thereby reducing co-channel interference. In an example, an available bandwidth is divided into twelve channel frequencies, so that a cell cluster includes four cells. Co-channel cells associated with half the channel frequencies are assigned to cells in the first row of cells, and the remainder are assigned to cells in the second row.

Abstract: A system designed to detect and identify fixed utility objects, such as telephone pedestals, power transformers, man-holes, anchor cables, and the like, that are hidden by heavy overgrowth of vegetation. The system provides for automatic look-ahead detection of such objects during mowing and clearing operations with heavy machinery using passive radio frequency transponder technology to both detect the immediate presence of a tagged object as well as basic identification of the type of object replying to the interrogation. The operator can be signaled audibly and/or visually when a tagged object is detected. The transmitter and antennae are mounted in the cab of a mobile machine for protection from physical damage. An integrated microprocessor performs the requisite algorithms needed to process the reply form one or more RFID (Radio Frequency Identification) tags and generate the alert signals for the operator alerts.

Abstract: A method for detecting portable objects from a network of N antennae controlled by a centralized management unit. Signals are simultaneously emitted by the management unit to all antennae. Resulting response signals from antennae that have detected a portable object are received by the management unit. Each object thus detected is successively selected from these signals according to a pre-established sequence. The invention applies in particular to access control.

Abstract: A system for ascertaining angle of arrival of an electromagnetic signal having at least one signal characteristic indicating a first state or a second state includes: (a) a plurality of n antenna elements intersecting a common axis and cooperating to establish 2n sectors; each respective sector being defined by two antenna elements and the axis; the signal characteristic indicating the first state on a first side of each antenna element and indicating the second state on a second side of each antenna element; combinations of the signal characteristics in each respective sector uniquely identifying the respective sector; and (b) an evaluation apparatus coupled with the antenna elements and employing the state of the signal characteristic sensed by each of the antenna elements to effect ascertaining angle of arrival to a resolution of at least one respective sector.

Abstract: In an interferometer system, a revolving antenna array is used to sufficiently resolve all ambiguities in determination of frequency and direction of arrival of a wave-front. The frequency and direction of arrival are determined by matching predicted phase difference codes with an actual code measured at the antenna array, utilizing a cross-correlation technique. The number of parameters that can be simultaneously uniquely determined by the system depends on if the antenna array is rotated in planar or conical surfaces, and if the cross-correlation is uni- or multi-dimensional. The antenna array may include more than one baselines to enhance the system sensitivity and finding capacity.

Abstract: A method and apparatus for estimating a communication channel in a wireless communication system having multiple transmitter antennas using reduced rank estimation. The method exploits redundant and/or a priori knowledge within a system to simplify the estimation calculations. In one embodiment, a covariance matrix is calculated and analyzed to determine if the channel parameters may be reduced for channel estimation. If not, all parameters are used, otherwise a reduced rank matrix is used for the calculation.

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 all angle sweep for arrival angle estimation of MUSIC method or the like.

Abstract: Methods and devices are disclosed for identifying objects over a surface and for tracking the position of said objects in relation to the sensing surface. The methods include the steps of providing an array of electrodes or coils that generating electromagnetic radiation having a individual characteristic frequencies of oscillation. Objects in proximity to the sensing surface(s) couple electromagnetically to the array of electrodes or coils, which then alters the characteristic frequency of one or more elements in the array. By monitoring the individual frequency shifts among the array elements, one or more objects in proximity to the surface can be sensed and identified. Quantitative identification and enhanced detection of the objects is achieved through the use of electromagnetic markers affixed or embedded in the objects in specified geometric patterns.

Abstract: A configurable directional antenna includes a center antenna element, a plurality of second antenna elements, and a switch matrix. Each second antenna element, together with the center antenna element, defines an antenna sector. A first portion of the second antenna elements is disposed at an inner radius around the center antenna element. A second portion of the second antenna elements is disposed at an outer radius around the first portion antenna elements. Each antenna sector comprises one of the radially inner antenna elements, one of the radially outer antenna elements, and a conductor extending between the one radially inner and the one radially outer antenna element. The switch matrix comprises first electronic switches for selectively grounding selected ones of the second antenna elements, and second electronic switches each for selectively connecting together the second antenna elements of one of the antenna sectors with the associated conductor.

Abstract: A system is provided for assisting in the detection and tracking of narrowband signals arriving at an antenna array operating over a wide detection bandwidth and in a crowded RF environment. Since the nature of the detection mission is constrained to be a general search, the system does not attempt to detect signals of interest via matched filtering mechanisms (i.e. training sets), but exploits general properties such as power, frequency, time and angle of arrival. For the purposes of providing sufficient Frequency/Time resolution as well as to avoid array overloading in the detection process, the digitized wideband streaming data is frequency channelized using a sufficiently high revisit rate for the signal set of interest, constrained by the required feature detection accuracy or environment adaption rates. Within each frequency subchannel, efficient array signal subspace tracking techniques are used to separate and track spatially separated cochannel signals.

Abstract: A user equipment related multicast/multicast/broadcast multimedia service information present in a serving radio network controller can be coupled with the multicast/broadcast multimedia service controlling radio network controller service context in the corresponding controlling radio network controller over the interface between the radio network controller entities.

Abstract: A system and method are provided that includes at least a pair of spaced antennas having overlapping fields of view. The system further includes at least a pair of receivers respectively coupled to the pair of antennas. Each of the receivers includes a spectral separator having a plurality of output signals. Each of the output signals represents a signal value at one of a plurality of predetermined frequencies. A plurality of analog to digital converters are coupled to a corresponding one of the spectral separators for respectively providing a digital representation of each of the output signals. A digital processor coupled to an output of each of the plurality of analog to digital converters calculates an angle of arrival of the transmitted signal in at least one dimension from the digital representations.

Abstract: Apparatus for receiving ranging signals (e.g. signals from Global Positioning System satellites) has a receiver coupled to a plurality of spaced antennas. The receiver includes a signal combiner which receives, from a processing circuit, signal components individually representative of a characteristic of the received ranging signals (e.g. signal-to-noise ratio) at a respective antenna and weights the said components to produce a range estimate of improved accuracy in difficult reception conditions. In one embodiment receiver includes a common i.f. channel which filters a combination signal representative of all the incoming signals in order substantially to maintain phase coherence between the incoming signals, yielding improvements in carrier phase measurement and discrimination.

Abstract: A system designed to detect and identify fixed utility objects, such as telephone pedestals, power transformers, man-holes, anchor cables, and the like, that are hidden by heavy overgrowth of vegetation. The system provides for automatic look-ahead detection of such objects during mowing and clearing operations with heavy machinery using passive radio frequency transponder technology to both detect the immediate presence of a tagged object as well as basic identification of the type of object replying to the interrogation. The operator can be signaled audibly and/or visually when a tagged object is detected. The transmitter and antennae are mounted in the cab of a mobile machine for protection from physical damage. An integrated microprocessor performs the requisite algorithms needed to process the reply form one or more RFID (Radio Frequency Identification) tags and generate the alert signals for the operator alerts.

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: An apparatus and method determining angle-of-arrival of a received radio frequency signal, and apparatus and method for calibrating the angle-of-arrival determining apparatus.

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: This disclosure describes an electronic support measures (ESM) system for estimating the angle of arrival of a signal which impinges on an array of antennas configured in a straight line. The antennas in the array are spaced such that the distances from the interior antennas to one of the end antennas—in terms of units of a reference length &xgr;—are relatively prime. The system does not require a priori knowledge of the signal radio frequency. In order to enhance the computational efficiency and ability of the system, a Diophantine processing algorithm is utilized. The set of antenna spacings is selected based upon minimizing the probability that this algorithm produces an ambiguity error in the estimated angle of arrival. The computational efficiency of the system is improved relative to current systems, as it requires only N2 real multiplications, where N+1 is the number of antennas in the array.

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 present invention uses feedback 300 from RF carrier frequency measurements 301 to disassociate the emitter angle-of-arrival component 313 in the ambiguous phase measurement 312 from the initially unknown phase measurement integer ambiguities 314; to then process 302 resolve the ambiguities; and finally to process 303 to obtain the correct emitter AOA. The present invention does this by converting the actual interferometer baselines 315 on which the unassociated pulse 308 phase measurements 304 were made at different emitter frequencies to a baseline set 305 for a single-frequency equivalent interferometer array. This conceptual array has the following property: the phase measurement 306 that would be made on it at the fixed frequency for a signal at the same direction-of-arrival 307 are identical to the actual phase measurements made on the physical array. Because of this equivalency the conceptual array is called the E(equivalent)-array.

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: An interferometer antenna system (32) for measuring the angle of arrival of RF signals. The interferometer antenna system (32) includes a plurality of interferometer antenna elements (36) coupled to a first switching network (42). The first switching network (42) is coupled to only two interferometer receivers (44, 46). The first switching network (42) selectively connects the plurality of interferometer antenna elements (36) in pairs to the two interferometer receivers (44, 46) in a sequential manner, so that a phase difference is measured between the received signal for several of the pairs of the interferometer elements (36). Additionally, a plurality of guard antenna elements (38) are coupled to a second switching network (48). A single guard receiver (50) is coupled to the second switching network (48), where the second switching network (48) selectively connects one of the guard antenna elements (38) to the guard receiver (50) in a sequential manner.

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: A method and apparatus for determining the azimuth and elevation angles of a signal from an emitter is provided. An antenna array receives the signal. The antenna array includes one or more pairs of antenna elements of like polarization mounted diametrically opposite each other in a ring. A switch receives the received signal from the antenna pairs. The switch outputs a processor-selectable number of signals. A radio frequency converter downconverts a processor-selectable number of signals. The converter outputs the downconverted signals. An intermediate frequency processor measures phase differences across the antenna pair baselines for the downconverted signals. The intermediate frequency processor outputs the measured frequency and phase difference data. An ambiguity resolution processor selects antenna pairs by controlling the switch. The ambiguity resolution processor receives the measured frequency and phase difference data from the intermediate frequency processor.

Abstract: A communication system has a primary radio station and a portable radio station. The primary radio station communicates with the portable radio station. The portable radio station is freely three-dimensionally orientable with respect to a fixed coordinate system. The portable radio station has a transceiver, a controllable antenna structure, and a beam directional controller for three-dimensionally controlling a beam radiated by the controllable antenna structure. The portable radio station further has a three-dimensional geometric sensor for three-dimensionally sensing a local magnetic field. The beam is controlled on the basis of the sensed local magnetic field.

Abstract: An apparatus and method for determining the angles-of-arrival and the polarization states of incoming RF signals of unknown polarization using five or more RF sensing antenna elements of differing yet known orientations of polarization.

Abstract: A TCAS receiver, including a relative bearing measurement radio receiving apparatus for use with an antenna array having four antennas where each antenna has associated with it, its own receiver capable of demodulating both I and Q components of transmissions from an intruding aircraft.

Abstract: The extraction of phase information for radio frequency (RF) direction of rival is attained by pre-detect sensing and quantization of differential phase of a RF wave impinging on two or more antenna apertures, based on sensing and encoding differential phase without the use of conventional detection, and quantizing phase at or near the leading edge of a pulse signal. This is accomplished by detection of an intermediate frequency (IF) carrier, and encoding leading-edge phase (for each channel) in terms of near-phase-difference between two reference-oscillator readings containing the differential phase information--encoded as differential reference-oscillator phase. Precision angle-of-arrival is then derived from the measured differential reference-oscillator phase.

Abstract: An apparatus and method for target-angle determination using lower-frequency radars having compact non-moving antennas over broad viewing sectors. Use of direction finding (DF) in place of beam forming and scanning eliminates the need for conventional, physically large phased-array antenna systems. The described DF algorithm advances the art over previously described least-squares DF by allowing numerically efficient and robust resolution of multiple targets at closely spaced angles. When used with coastal HF ocean surface current and wave monitoring radars where sea echo is the target, the method extracts complex current patterns. The high degree of singularity of the antenna signal covariance matrix is exploited and used as the basis for extracting angles with minimal averaging. More receive antenna elements can be added at convenient locations to handle more complex target angle scenarios.

Abstract: A radio direction finder based on the simulated Doppler frequency shift principle is disclosed that is applicable to FSK encoded pulsed transmissions. Typical applications include tracking of stolen vehicles or shipped package tracking. During FSK decoding, all antenna elements of the antenna array are turned on in a non-rotating mode thus eliminating error due to the simulated antenna rotation modulation while providing enhanced gain for the FSK decoder circuit. After decoding a suitable FSK signal, a virtual antenna rotation is enabled, and the bearing is measured during the time interval when the transmitter is only broadcasting a carrier wave.

Abstract: An apparatus and method for determining the angles-of-arrival and the polarization states of incoming RF signals of unknown polarization using three or more RF sensing antenna elements of differing yet known orientations of polarization.

Abstract: Aircraft-mounted Identification Friend or Foe (IFF) antennas employ a linear array of radiator elements positioned transverse to the boresight axis. With an azimuth determination capability, but lacking elevation resolution, such antennas are subject to coning errors in determining the azimuth bearing of a target at an altitude differential. With use of a linear array (10) of multi-radiator elements (11, 12, 13), an output signal (23) having the characteristic of an amplitude which increases for off-boresight targets is provided. That signal is compared to a typical form of antenna system output signal (22), which has an amplitude which decreases for off-boresight targets. By such amplitude comparison, the angle (.beta.) to a target is determined and used to provide an azimuth correction factor (53). An apparent azimuth bearing (54) subject to coning error can then be corrected (55) to provide the true azimuth angle to a target (56).

Abstract: The method and apparatus precisely identifies and locates an object which resonates in response to signals of at least one and, more typically, two resonant frequencies. The locating apparatus includes a transmitter for concurrently transmitting signals having a resonant frequency and signals having a non-resonant frequency toward the resonant object. The locating apparatus also includes at least two receivers for receiving reflected signals having the resonant frequency and the non-resonant frequency. The locating apparatus further includes a signal processor for locating the resonant object based upon the reflected signals detected by the receivers. The signal processor has multiple channels, one of which is associated with each receiver, for separately processing the reflected signals received over time by each of the receivers.

Abstract: Apparatus and a processing method that determine accurate angle of arrival data indicative of the direction to an emitter. An accurate angle of to the emitter using four antennas and receiver channels (processor). The present invention provides for an ambiguity function that is an implementation of a four-channel two-dimensional interferometer array. The interferometer array and method provide for a reference antenna and second, third and fourth antennas disposed in a predetermined plane with the reference antenna and offset from the reference antenna at locations such that no two antennas lie along a straight line that includes the reference antenna. Receivers are coupled to the antennas for detecting RF energy derived therefrom. Phase comparators make three phase difference measurements (.phi..sub.1, .phi..sub.2 and .phi..sub.3).

Abstract: A method is described modifying initially linear or planar interferometer arrays such that the arrays can be placed in conformal installations. The method commences with a conventional linear or planar array design and then using certain techniques and relationships allows for the possibility of antenna placement with materially reduced restrictions. A plurality of phase equivalent antenna locations obeying prescribed relationships are generated. These positions lie on the conformal surface on which the array is to be mounted. This permits an optimal set of antenna positions to be chosen based on operational requirements.

Abstract: A system for the instantaneous determination of the frequencies and angles of arrival of a plurality of simultaneously incoming signals. The system includes beam network matrix for receiving the simultaneously incoming signals, the matrix providing one or more superimposed output signal which includes phase information associated with the angles of arrival of the signals. The system uses a Fourier receiver which includes a sampler means for periodically producing a sample of the superimposed output signals and a frequency differentiator for differentiating the sample by frequency into a train of discrete waveforms. Each of the train of discrete waveforms is associated with one of the incoming signals and includes phase information associated with one of the incoming signals. The Fourier receiver further includes a mechanism for determining frequency which determines from one of the train of discrete waveforms the frequency of one of the incoming signals.

Abstract: A solution to the AOA problem is provided, receiving the data via a plurality of antennas, which uses a switching network to couple the antennas to a single receiver and a single analog-to-digital converter to digitize the incoming signal. It is possible to solve the problem where there might be multiple signals present. In the receiver, the incident radiation is mixed with a local oscillator signal and down converted to an intermediate frequency (IF). This IF signal is discretely sampled in the analog-to-digital converter, and further processing is done using digital techniques. The incoming signal has to be phase compared to obtain the angle of arrival. Different delay times are used to receive the digital data from the different antennas at the same sampling times, with the data aligned according to the time axis. The frequency of the incoming signals can then be detected by performing a Fast Fourier Transform (FFT) on the data from one antenna with respect to time.

Abstract: The invention provides a method for using single linear arrays for making AOA measurements only in sensor coordinates to perform emitter direction finding from an observing aircraft.

Abstract: A device and method for reconstructing a vector wave and its source direction by measuring the amplitudes of the vector wave in directions chosen according to a necessary and sufficient condition that ensures that the measured amplitudes contain enough information to provide a unique set of relative phases among the sinusoidally time-varying components of the vector wave. Together with the amplitudes, these relative phases are processed by a microprocessor to yield the polarization characteristics of the vector wave and the direction of its source.

Abstract: In an antenna array of N elements in a circle around a large through mast, direction finding capabilities are enhanced for an incoming signal where fewer elements are needed compared to standard quasi-Doppler or pseudo-Doppler methods. Azimuth detection takes advantage of the scattered wave from the through mast where measurements of amplitude and relative phase shift shows an induced distortion pattern from through mast scattered waves. Analyzing the amplitude and phase measurements determines the azimuth angle of the arrival of the incoming signal.

Abstract: An apparatus and method for determining the direction of origin of a received transmission signal using a spinning antenna pair generally provides the steps and apparatus for measuring the phase difference between signals simultaneously received, coarsely approximating the direction of origin of the transmission signal, reconstructing a phase difference signal using the measured phase differences and a calculated signal based upon the coarse approximation, correcting the reconstructed phase signal based upon the first derivatives of the reconstructed signal and the calculated signal, and determining the direction of origin based upon the corrected reconstructed phase signal.

Abstract: The present invention concerns an apparatus and method for measuring the azimuth and elevation of an object. The apparatus includes a platform; a base plate arranged to the construction of the platform rotatably in a plane, which is essentially horizontal; a sensor frame attached to the base plate; at least three sensor elements attached to the sensor frame; and an electronics unit for the control of the sensor elements, capable of performing the processing of signals received by the sensors. The sensor frame is rigidly attached to the base plate and the directional pattern of the sensor elements is such as to cover the entire angle span of interest in the elevation plane, while the pattern covers an essentially narrower angle in the azimuth plane. The direction finder does not easily lose the tracked object performing movements particularly in the elevation plane.

Abstract: A signal processor for radar systems having phased array antenna structures. The processor determines the angle of arrival of the signal from a discrete energy source. The separate elements or output ports of the antenna structure are sampled to form a matrix of signal values. These values are converted into polynomial expressions consistent with one of the spectral estimating methods of maximum entropy, maximum likelihood, and thermal noise. The roots of the polynomial expressions are found and compared to the distance of the unit circle in a pole-zero diagram. Roots sufficiently close to the unit circle are selected as representative of the source signal peaks and the angular directions to such sources are determined by the corresponding angular location of the selected roots in the pole-zero diagram.

Abstract: In, for example, a passive direction-finding radio receiver employing a multi-beam antenna which has e.g. ninety-six feeds which form a corresponding number of overlapping reception beams, the output signal amplitudes of the various feeds can be compared with a reference to yield a sequence of binary digits, e.g. as shown in FIG. 2. The position of a radio source is given by the position in the sequence of the center of the largest group of "1"s. In order to quickly determine this position the sequence is subjected repeatedly to a processing operation in which each "1" which does not have "1"s as its two immediate neighbors is changed to a "0", thereby repeatedly stripping the two end "1"s off each group of "1"s until none remain. The required position is that of the single "1" or pair of "1"s present immediately before all have become "0"s.

Abstract: An adcock DF-on-the-fly type direction finding system employing a beam forming dispersive delay line (BFDDL). A square array of four elements A1, B1, C1, and D1 with A1, C1 and B1, D1 being the diagonal pairs is used to input signals to combiner, shifter and summer elements to produce signals representing S.sub..phi. =A1+B1+C1+D1 and S=(B1-D1)+[(A1-C1) shifted -90.degree.]. S.sub..phi. and S are input to the BFDDL which produces output signals sampled from the output spatial interference pattern of the BFDDL at 90.degree. intervals. The output signals from the BFDDL are used to calculate the arrival of the signal of interest as being substantially equal to the phase shift between S.sub..phi. and S.

Abstract: A signal-acquisition system (10) for a circular antenna array (12) includes a two-dimensional compressive receiver (18) that performs a two-dimensional Fourier transformation in time and position on the outputs of the array. Each of the outputs of the compressive receiver (18) is fed to input ports of several processing units (24), which multiply them by an appropriate time-dependent function. The resultant modified signals are then processed by Butler matrices (30) that together have a matrix of output ports (32). Each output port is associated with a different combination of azimuth and elevation angles. A signal source at given azimuth and elevation angles with respect to the array (12) causes its greatest response in the output port (32) associated with those angles.

Abstract: A passive instantaneous microwave signal frequency identifying and angle of arrival identifying system employing a beam steering multiple element antenna coupled through a Butler matrix to a plurality of simplified Fourier transformation radio receivers wherein unit value or near unit value magnitudes of the Kernel function ⅇ - j2 ⁢   ⁢ π ⁢   ⁢ kn N in the receivers' Fourier transformations are used to elude transformation computation complexity and resulting radio receiver size and cost penalties. Limiting amplifiers, a video signal path and direction finding encoding logic are also employed. Airborne military application of the system in electronic warfare direction finding, radar frequency determination and other activities is included.