Abstract: A method, an electronic device or customer-premise equipment, and a computer readable medium are disclosed for estimating a sound source. The method includes detecting, on an electronic device, voice data from a space; calculating, on the electronic device, an estimated voice source location from the detected voice data; detecting, on the electronic device, wireless location data from a positioning system within the space; calculating, on the electronic device, a probability of a user within one or more regions from the calculated estimated voice source location and the detected wireless location data, the one or more regions being regions of a plurality of regions within the space; and steering, from the electronic device, a microphone array for voice detection toward the one or more regions having the probability of the user within the one or more regions.

Abstract: A radar system and method are provided for reducing multipath interference signals. The multipath interference signals can be reduced by the radar system emitting electromagnetic waves that creates a null in the direction of expected multipath interference signals, such that the multipath interference signals are void (or substantially void) from signals received by the radar system.

Abstract: An antenna beam tracking system has dynamic interference reduction. The system includes antennas that can form multiple beams, each beam of which can continually track or point its beams independently in various angular directions. A first beam continually tracks and receives (downlink) signals from a desired source or node such as a satellite or terrestrial node which generally has an apparent motion relative to the antenna. A second beam continually tracks and receives potentially harmful interference signals that may arise from different directions. The signals of the second beam are dynamically coupled to the signals in the first beam in such a manner as to effect cancellation or substantial reduction of the interference.

Abstract: Communication signals using a first and a second frequency band in a wireless network is described herein. The first frequency band may be associated with a first beamwidth while the second frequency band may be associated with a second beamwidth. An apparatus may include receiver circuitry arranged to receive first signals in a first frequency band associated with a first beamwidth and second signals in a second frequency band associated with a second beamwidth, the first signals comprising a frame synchronization parameter and the second signals comprising frame alignment signals. The apparatus may further include processor circuitry coupled to the receiver circuitry, the processor circuitry arranged to activate or deactivate the receiver circuitry to receive the frame alignment signals based on the frame synchronization parameter. Other embodiments may be described and/or claimed.

Abstract: A reconfigurable holographic antenna and a method of shaping an antenna beam pattern of a reconfigurable holographic antenna is disclosed. A baseline holographic pattern is driven onto a reconfigurable layer of the reconfigurable holographic antenna while a feed wave excites the reconfigurable layer. An antenna pattern metric representative of a baseline antenna pattern is received. The baseline antenna pattern is generated by the reconfigurable holographic antenna while the baseline holographic pattern is driven onto the reconfigurable layer. A modified holographic pattern is generated in response to the antenna pattern metric. The modified holographic pattern is driven onto the reconfigurable layer of the reconfigurable holographic antenna to generate an improved antenna pattern.

Abstract: A radar system having side lobe blanking capability is disclosed. The system can include a single channel antenna and receiver system, the side lobe blanking system being time multiplexed, but requiring no dedicated guard channel data collection period such that the scan rate of the system is not degraded.

Abstract: Provided are a radar system for a vehicle and a method for measuring an azimuth therein, which are capable of increasing target sensing and tracking reliability by blocking an error signal that is input from the ground where no vehicle exists or in the elevation angle direction. A system for blocking an error signal input from a ground or in an elevation angle direction includes: two or more main reception antennas; a single side lobe suppression antenna; and a radar configured to compare a magnitude of a main reception signal received from the main reception antenna with a magnitude of a side lobe suppression reception signal received from the side lobe suppression antenna, and measure an azimuth of a target by using the received main reception signal when the magnitude of the main reception signal is larger than the magnitude of the side lobe suppression reception signal.

Abstract: A communication device is described comprising a first transceiver chain set to communicate signals in a first frequency range, a second transceiver chain set to communicate signals in a second frequency range or set to no communication and a controller, configured to receive an instruction for a resetting of carrier aggregation comprising a setting of the first transceiver chain or the second transceiver chain to receive signals in a third frequency range different from the first frequency range and the second frequency range, to control, in response of the reception of the instruction, the second transceiver chain to receive signals within the first frequency range simultaneously with the first transceiver chain and to control the first transceiver chain, when the communication of signals within the first frequency range by the second transceiver chain fulfills a predetermined criterion, to stop communication of signals within the first frequency range.

Abstract: A method of for processing signals in a radar system is shown comprising an antenna system having at least two antenna elements, a beam forming arrangement (ABF_RX, ABF_TX) for selectively steering the directivity of the antenna system in a given selected direction, the directivity of the antenna system having a main lobe in the selected direction and a back lobe (BL) in another direction and of a lower magnitude than the main lobe. By utilizing various scale and subtract processing both noise levels and ghost signals can be considerably reduced. A SAR radar apparatus has moreover been shown.

Abstract: A system has a stratospheric platform with a payload controller and a phased array antenna having a plurality of elements. A gateway station communicates with the stratospheric platform. The gateway station scales the plurality of elements to form a reconfigurable plurality of beams. The gateway station communicates a control signal to the stratospheric platform to communicate a scaling of the elements. The stratospheric platform configures the elements of the phased array antenna according to the scaling using adaptive interference rejections.

Abstract: This invention relates to the use of a sufficiently-sampled auxiliary array in combination with one or more under-sampled sub-arrays. The sufficiently-sampled auxiliary array is used to create a signal-free reference (SFR) beam that contains grating lobe interference. The SFR may be used to cancel the interfering grating lobe in an under-sampled main beam by coherently eliminating or subtracting the SFR from the main beam. Exemplary aspects of the invention thus support significant under population of the full aperture and avoid the problems and limitations of previous solution, with consequent savings in sensor hardware cost and weight.

Abstract: A phase cancellation circuit for a cavity filter including a sampler loop assembly arranged to receive an input signal, a variable loop assembly connected to the sampler loop assembly by a cable, wherein the variable loop assembly is arranged to transmit an output signal from cavity filter, wherein the sampler loop assembly samples a cancellation signal at an isolation frequency from the input signal and transmits the cancellation signal to the variable loop assembly via the cable, and, wherein the cable has a length equal to a multiple of a half-wavelength at the desired isolation frequency, wherein the cancellation signal undergoes a 180° phase shift by traveling through the cable, wherein the variable loop assembly combines the cancellation signal with the input signal to cancel the input signal at the isolation frequency due to the 180° phase shift for creating the output signal with a notch at the isolation frequency.

Abstract: A novel adaptive beamforming technique with enhanced noise suppression capability. The technique incorporates the sound-source presence probability into an adaptive blocking matrix. In one embodiment the sound-source presence probability is estimated based on the instantaneous direction of arrival of the input signals and voice activity detection. The technique guarantees robustness to steering vector errors without imposing ad hoc constraints on the adaptive filter coefficients. It can provide good suppression performance for both directional interference signals as well as isotropic ambient noise.

Abstract: A cosite interference rejection system allows cancellation of large interfering signals with an optical cancellation subsystem. The rejection system includes an interference subsystem coupled to a transmit system, where the interference subsystem weights a sampled transmit signal based on a feedback signal such that the weighted signal is out of phase with the sampled transmit signal. The optical cancellation subsystem is coupled to the interference subsystem and a receive antenna. The optical cancellation subsystem converts an optical signal into a desired receive signal based on an interfering coupled signal and the weighted signal. The weighted signal is therefore used to drive the optical cancellation subsystem. The rejection system further includes a feedback loop for providing the feedback signal to the interference subsystem based on the desired receive signal.

Abstract: A positioning system receiver is disclosed. The positioning system receiver includes an antenna for receiving radio frequency (RF) signals. The positioning system receiver also includes a radio frequency front end system configured to convert the received RF signals into intermediate frequency signals. The positioning system receiver further includes a digital processing and correlation system, receiving the intermediate frequency signals and including a plurality of taps on the autocorrelation function main lobe and a plurality of taps on at least one of the autocorrelation function side lobes. The digital processing and correlation system uses the signals received from the taps in a dot product detector algorithm to improve the signal-to-noise ratio of the receiver system.

Abstract: Methods and apparatus for improving the effective resolving power of an array antenna are described that are not limited by the physical characteristics of the array. In an array with M elements, up to M?1 directional vectors may be selected, preferably at angles corresponding to the main lobe and/or side lobes of an array antenna beam pattern. A received signal plus interference (s+i) is zero-transformed to eliminate interference received from the plurality of selected directions. The zero-transformed s+i is then restored to obtain the signal of interest observed at maximum gain undisturbed by interference incident from arbitrarily close signal sources. The approach may be combined with conventional beamforming techniques to remove interference incident from angles corresponding to the side lobes, where conventional beamforming techniques are most effective.

Abstract: Transmitting apparatus (10) for transmitting a transmission signal to a receiving apparatus (12) is described. The transmitting apparatus (10) comprises means (30, 32, 34) for transmitting to the receiving apparatus a plurality of transmission beams in accordance with a transmission beam pattern, at least one of the beams carrying the transmission signal, each beam being distinguishable from the or each other beam, means (38, 40) for receiving from the receiving apparatus a feedback signal based on measures of the quality of the transmission beams received at the receiving apparatus, and means (36) for adjusting the transmission beam pattern in dependence on the feedback signal. Corresponding receiving apparatus, and corresponding methods are also described.

Abstract: A scanning antenna diversity system for mobile FM radio having an antenna system with controllable logic switch, wherein a different high-frequency reception signal is passed to a receiver. An IF signal turns on a diversity processor, which switches the logic switch into a different switching position in response to reception interference. The diversity processor has two interference detectors whose signals are passed to a logic circuit for evaluation and to produce a logic control signal, so that a different switching positions are selected at the earliest possible time after the occurrence of interference in the reception signal.

Abstract: Generating a secondary beam (11) slightly offset from the main data collection beam (9) and obtaining hot clutter reference to be used in a conventional side lobe jammer processing algorithm (31). Advantage is taken of the typical geometries of a standoff jammer (1) which provides nearly matched dispersion characteristics of the jammer RF when viewed with the two received beams. The important parameter is dispersion relative to the received bandwidth. The secondary beam, which may be identical copy of the main beam except for target information, is placed offset by approximately two beam widths toward the jammer. The offset distance is chosen so that there is minimal and preferably no overlap in the main beam footprint on the ground but is as close as possible thereto. If there is overlap, then there is a chance that the target will appear in both beams and therefore be suppressed.

Abstract: This invention discloses an interference cancellation method based on smart antenna, which can solve various interference in mobile communication systems such as multipath propagation, etc., while using smart antenna. The invention includes the steps of: with a beam forming matrix, beam forming the output signal of a receiver based on smart antenna, then getting a set of digital signals NRk(m); canceling other users main path signal included in NRk(m), then getting another set of digital signals NSk(m), which only includes needed signals and all interference signals; searching in digital signal NSk(m) and getting all multipath interference signals coming from other users; canceling other multipath interference signal in NSk(m); and superposing the user main path and each multipath signal in phase coincidence, then getting a digital signal with interference canceled.

Abstract: An interference canceller capable of reducing interference between users by generating appropriate replicas. This canceller carries out a hard decision on a signal after FEC decoding and carries out error detection on the resulting signal, and, when an error is detected, generates a replica with a smaller weighting factor assigned to an erroneous signal or generates a replica using a provisionally detected value prior to FEC decoding (hard decision value or soft decision value). Or when the error detection result in the previous stage is OK, the canceller generates a replica using the hard decision value in the previous stage.

Abstract: A weaker signal receiving system inclusive of stronger nearby-sourced interference signal cancellation capability. Stronger interference signal cancellation is accomplished by actively canceling or subtracting from the received signal an intermediate signal in which the weaker signal has been attenuated but the stronger signal remains. Attenuation of the weaker signal in this intermediate signal is accomplished in a feedback loop arrangement by an amplitude-responsive signal processing element embodied from for example a ferrite material such as yttrium iron garnet disposed in a physical wave propagating and wave amplitude sensitive film. The cancellation or subtracting is accomplished using received signals and without need for a direct output sample of the stronger signal at its source. Military aircraft use of the disclosed system in the microwave and other spectral regions with transmission mode as opposed to reflection mode signal amplitude discrimination by the ferrite device is included.

Abstract: A digital beamforming network for transmitting a first number of digital information signal using a second number of antenna array elements is disclosed. Assemblers are used for assembling one information bit selected from each of the information signals into a bit vector. Digital processors have an input for the bit vector and a number of outputs equal to the second number of antenna elements and process the bit vector. Finally, modulation waveform generators coupled to each of the second number of outputs generate a signal for transmission by each antenna element.

Abstract: Weighting coefficients for a phased array antenna are iteratively refined to optimal values by a ‘bootstrapped’ process that starts with a coarse set of weighting coefficients, to which received signals are subjected, to produce a first set of signal estimates. These estimates and the received signals are iteratively processed a prescribed number of times to refine the weighting coefficients, such that the gain and/or nulls of antenna's directivity pattern will maximize the signal to noise ratio. Such improved functionality is particularly useful in association with the phased array antenna of a base station of a time division multiple access (TDMA) cellular communication system, where it is necessary to cancel interference from co-channel users located in cells adjacent to the cell containing a desired user and the base station.

Abstract: A system for instrumenting time sampled predicting interference suppression, particularly in a side-lobe canceller system. Main and auxiliary channel signals are supplied to a canceller loop where correlating weights are sampled just prior to a radar pulse transmission on command of a radar pretrigger pulse. A sampling circuit stores both current and past weights and combines the current weight with the integral of the difference between the current and past weight to form predicting weights over each pulse repetition period. The predicting weights are used to form a translating signal for operating on the auxiliary channel interference signal so that it will cancel the interference in the main channel. By sampling just prior to radar pulse transmission and forming the predicting weights, cross modulation of clutter and antenna scan error can be reduced in order that a side-lobe canceller may be used compatibly with Moving Target Indicators.

Abstract: A high capacity broadband base station employs a wideband radio and phased array processing subsystem. This phased array antenna subsystem contains multiple sets or pairs of alternating receive only and transmit/receive elements distributed in a two dimensional spatial array. Each digital wideband radio performs both receive and transmit channel signal processing. In the receive direction, the digital representation of the entire spectrum for each antenna element is divided into channels for the particular waveform of interest. For a 5 MHz PCS GSM, the digital wideband radio separates twenty-four carriers into twenty-four (200 KHz wide) data streams, each of which is representative of a respective channel, and couples each channel to a digital signal processor. In the transmit direction, the radio combines the digital representations of the twenty-four individual channels supplied by the DSP into a single wideband channel for transmission.

Abstract: Weighting coefficients for a phased array antenna are iteratively refined to optimal values by a ‘bootstrapped’ process that starts with a coarse set of weighting coefficients, to which received signals are subjected, to produce a first set of signal estimates. These estimates and the received signals are iteratively processed a prescribed number of times to refine the weighting coefficients, such that the gain and/or nulls of antenna's directivity pattern will maximize the signal to noise ratio. Such improved functionality is particularly useful in association with the phased array antenna of a base station of a time division multiple access (TDMA) cellular communication system, where it is necessary to cancel interference from co-channel users located in cells adjacent to the cell containing a desired user and the base station.

Abstract: An adaptive beamformer and signal processor for sonar and other signal receptor arrays, in which beamforming is accomplished by correlation feedback loops providing matched weighting across the array. To constrain the adaptive beamformer thus comprised against cancellation of useful signals from a particular angular region, which normally is the beam mainlobe or boresight region, one or more spatial notch filters are interposed within the correlation feedback loops for preventing signal suppression within such angular region.

Abstract: The disclosed method uses the ancillary antennas of a radar, and consists in determining the positions of the phase centers of these ancillary antennas, compensating for the difference in optical path between the reflection lobe of the processed channel and that of the ancillary channel, and generating a synthetic channel by an SLO type processing in performing a coherent subtraction between the processed channel and the ancillary channels used, on the desensitized zone of the doppler distance/frequency ambiguous domain of each of the processed channels.

Abstract: Without use of separate auxiliary antennas, adaptive nulling automatically reduces jamming or other interference affecting a radar or IFF system. A primary beam forming network utilizes four-port directional coupler devices, each having an ancillary port which would have been resistively terminated in the absence of the invention. Signals from ancillary ports are coupled to an auxiliary beam forming network to form auxiliary beam patterns which are orthogonal to and track steered main beam patterns. Auxiliary signals are received via the auxiliary beam patterns. Least mean square (LMS) control loops operate on a feedback basis to derive weighted auxiliary signals responsive to jamming signals. The weighted auxiliary signals are combined with the primary received signals (which may be sum and difference signals) in reverse polarity, so as to be additively destructive of the jamming signals. Multiple LMS control loops enable nulling of jamming signals simultaneously in sum and difference channels.

Abstract: This invention relates to automatic direction finding methods and systems for an electromagnetic or acoustic signal source by utilizing the concept of adaptive nulling of a narrow or wideband signal received by one sensor from the same signal received by the other, along with appropriate adjustments, in a two-sensors-interferometer. Plurality of sensors can be used to measure two orthogonal angles of arrival of a signal. Inventive methods and devices permit singling out a particular signal of interest among others by allowing a frequency tuning and selective amplification of the particular signal of interest without destroying the differential phase or time delay between the signals received by the sensors that determine the angle measurement. A high degree of signal cancellation during the adaptive nulling process permits a correspondingly high degree of accuracy and resolution for the angle measurement and also permits a relatively short baseline for the interferometer.

Abstract: The invention pertains to the sensing and elimination of jamming signals transmitted by jammers towards radar antennas. According to the invention, we associate with a main space surveillance radar antenna an auxiliary antenna that is outfitted with a modulating filter which enables the sensing of jammers, and the elimination of jamming effects by opposing, to the secondary lobes of the main antenna corresponding to the jamming directions, corresponding secondary lobes which are appropriately amplified by the auxiliary antenna. The invention applies to anti-jamming of radar antennas with mechanical or electronic sweeps.

Abstract: A radar interference circuit which rejects both continuous noise and shorulse interference signals. A plurality of omni-directional antennas are placed around the main directional radar antenna and connected in differing sets to a plurality of canceller means to each of which the main antenna signal is also connected. The canceller means for each set of three Omnis and the main antenna cancels out the white-noise interference received by that group of antennas. The outputs of the plurality of canceller means are then taken in different sets of two each, subtracted and compared to a threshold signal. If one or more comparator outputs are above the threshold, signifying that the antenna pulse signal is being received through the sidelobes of the antenna patterns, the outputs of these comparators will be a one signal and the OR gate, to which the comparator outputs are fed, will provide an output to blank the radar.

Abstract: A sidelobe canceler includes a main antenna, an array of sub-antennas, a subtractor having a first input connected to the main antenna, a main-array processor and M sub-array processors. The main-array processor multiplies the outputs of the sub-antennas with weight coefficients using correlations between the sub-antenna outputs and the subtractor output and combines the multiplied signals into a signal, which is coupled to the second input of the subtractor. The signal-to-noise ratio of the subtractor output is maximized by an adaptive matched filter. Each sub-array processor multiplies the sub-antenna outputs with weight coefficients using correlations between the sub-antenna outputs and a decision signal. The multiplied signals are summed to produce an output of each sub-array processor, which is combined with the outputs of the other sub-array processors into a first diversity-combined signal, the latter being combined with the matched filter output to produce a second diversity-combined signal.

Abstract: A technique for improving sidelobe canceller performance by blocking the canceller output signal upon sensing reduced main channel interference accompanied by an increased sidelobe canceller output. Two signal processing networks form the difference between successive output signals from a radar antenna and sidelobe canceller respectively. The difference signals are multiplied together and the product used to control passage and preclude utilization of the canceller output signal when reduced jamming interference occurs.

Abstract: An improvement in monopulse radar achieves nulling of multiple mainlobe jammers while maintaining the angle measurement accuracy of the monopulse ratio by using multiple simultaneous beams, thereby obtaining the additional degrees of freedom necessary for cancelling more than one mainlobe jammer (MLJ). The beams are placed one null beamwidth apart in order to maintain orthogonality. The MLJs are nulled in the orthogonal direction of the angle estimate giving undistorted monopulse ratios.

Abstract: In a sidelobe canceller, a main channel multiplier (11) operates on the baseband output signal of a main antenna (10) with a weight signal to produce a weighted main channel signal. The baseband output signals of auxiliary antennas (16.sub.1 .about.16.sub.n) are adaptively weighted so that the auxiliary antennas have a first directivity pattern (44) whose main lobe oriented toward an undesired signal and summed together to produce a first sum signal (y.sub.s), and further adaptively weighted so that the auxiliary antennas have a second directivity pattern (45) whose main lobe is oriented toward a desired signal, and summed together to produce a second sum signal (y.sub.d). The second sum signal (y.sub.d) is summed with the weighted main channel signal to produce a diversity combined signal (y.sub.c), and the first sum signal (y.sub.s) is subtracted from the diversity combined signal (y.sub.c) to produce a sidelobe cancelled signal (y.sub.z).

Abstract: Improved radar system performance in a jamming environment is achieved by detecting the AM difference frequency produced by the beating of the desired radar signal with the jamming signal and applying same to one input of a balanced modulator while simultaneously applying the received signal (containing both the desired radar signal and the jamming signal) to the other input of the balanced modulator whereby the output from the balanced modulator contains the desired signal but not the jamming signal.

Abstract: An interference suppression system for cancelling undesired signals recei through the mainlobe of an antenna as well as its sidelobes. The interference suppression system has a main channel input having high gain for receiving desired signals and undesired signals and forming a main channel waveform, and an auxiliary channel input having low gain for receiving desired signals and undesired signals and forming an auxiliary channel waveform. A control circuit senses the relative undesired signal power in the two channels and responds by switching the waveforms in the two channels between two inputs of an interference-reducing circuit according to whether sidelobe or mainlobe interference is present in the main channel.

Abstract: An improved countermeasure detection system and technique for determining e range and azimuth of a noise jammer in a radar environment. A signal limiter is inserted into the output loops of a conventional multi-loop side-lobe canceller system such that the loops only respond to interference signals in the main lobe of a radar antenna as it sweeps through the jamming source. Each of the loops develops a weighting signal that is a measure of the absolute phase of the interference signal at an auxiliary antenna with respect to the phase center of the main radar antenna. By using two or more weighting signals and the known placement of each auxiliary antenna relative to the main radar antenna, the range and azimuth of a jammer can be calculated using available processing equipment to solve simultaneous equations.

Abstract: A digital, open-loop, sidelobe canceller system includes an arrangement of uxiliary-channel preprocessing cancellers and a series of main-channel cancellers in which specific cancellers average a different number of samples for cancelling both barrage (continuous) jamming and false-target-repeater jamming, which enter the sidelobes of a radar antenna. The preprocessing cancellers and each of the main-channel cancellers, except the last succeeding main-channel canceller, use long-time averaging (averaging over a large number, n, of samples of the main and auxiliary signals, where n>>2) for removing barrage jamming from the main signal. The last succeeding main-channel canceller uses short-time averaging (averaging over approximately 2-4 samples) for removing false-target-repeater jamming from the main signal.

Abstract: An antenna subject to standoff sidelobe barrage jamming exhibits a null in its sidelobe structure at a selectable elevation angle for all azimuth angles of interest. The null can be set to the elevation angles corresponding to the angle of the standoff jammers. The null is generated with the aid of an interferometer associated with each column of the antenna array. The interferometer produces a pattern having a plurality of lobes. The interferometer pattern is phased and amplitude adjusted relative to the antenna pattern of its associated column line array so that subtraction of the patterns causes one or more sidelobe of the antenna pattern to be at least partially canceled. An azimuth beamformer combines the elevation patterns of a plurality of column arrays, each connected to its own interferometer, to produce a pencil beam with a sidelobe structure exhibiting a null at the particular elevation angle.

Abstract: A system for instrumenting time sampled interference suppression, particuly in a side-lobe canceller system. Interference signals are sampled just before a radar transmits on command of a sample gate or radar pulse, with main and auxiliary channel signals being delayed by the time between two successive samples. The two samples are then combined to allow interpolation such that weighting functions can be formed to adjust the delayed auxiliary signal so that interference in the delayed main channel signal can be suppressed at all times. By sampling just prior to radar transmission and interpolating between samples, cross modulation of clutter, and antenna scan error can be reduced in order that a side-lobe canceller system may be used compatibly with Moving Target Indicators (MTI).

Abstract: The elimination of jamming signals from received radar signals is conventionally accomplished by side lobe cancellation techniques. Large interfering signals caused either by clutter or other sources, however, can cause intolerable degradation of coherent side lobe cancellation (CSLC) systems. In the present invention an inhibit signal is used to open the input to the coherent side lobe cancellation error sensing circuits thus preventing large signals from entering the coherent side lobe cancellation loop. Large signals entering coherent side lobe cancellation loops give rise to erroneous transients in the output. The invention effects storage of previously sensed error signals so as to continue jammer cancellation until new data become available to update the error signals. The inhibit signal is generated by a combination of coherent side lobe cancellation sensing circuits and logic control circuits that determine when an inhibit signal should be generated.

Abstract: A multi-carrier communication system wherein a sender side apparatus and a receiver side apparatus are connected through a transmission line. The sender side apparatus contains a multi-carrier modulator for modulating data, where preset numbers of bits of the data are respectively modulated with a plurality of carriers in each cycle. The sender side apparatus transmits a training signal which is modulated by the multi-carrier modulating unit where the numbers are set equal to a predetermined maximum of the numbers, to the receiver side apparatus. The receiver side apparatus evaluates the quality of components of the training signal where the components are modulated with the respective carriers to determine the above numbers to be preset, ciphers information on the numbers, and transmits the ciphered information to the sender side apparatus. The sender side apparatus deciphers the information to obtain the determined numbers, and presets the numbers in a multi-carrier demodulator which is provided therein.

Abstract: A method of preserving targets in the clear in an adaptive baseband MTI radar system with pulse compression is disclosed. The angle of the weighting signal is determined from the inverse tangent of the inphase and quadrature components of the weighting signal. This angle is then compared to a threshold angle in order to generate a modified weighting signal.

Abstract: An interference cancellation system has a combiner which removes an undesired component from a main signal including both a desired signal and an undesired signal received by a main antenna. A power sensor measures output power of a main signal. A weight control circuit is coupled with an output of the power sensor. An auxiliary antenna receives an undesired signal. A variable complex weight control circuit adjusts an undesired signal from the auxiliary antenna according to the output of the weight control circuit to provide an input signal to the combiner. The variable complex weight control circuit operates so that the output power becomes a minimum.

Abstract: Sidelobe jamming in dual diversity troposcatter link receivers is effectively suppressed by providing an auxilliary low power antenna, the output of which is differenced from the high power main antenna signals prior to processing in the receivers's dual diversity demodulator. The auxilliary antenna power is substantially equal to the sidelobe power of the main antennas. The auxilliary antenna receives jamming power that is comparable to the jamming power received by the main antennas. However, it receives much lower desired signal power. Differencing of the signals therefore, cancels jamming power with minimal effect on the desired signals.

Abstract: A beam is directed to an interfering source to obtain the best estimate of this signal. The beamformer output is fed into an inverse beamformer in such a way that the total delay experienced by a signal from any element of the array is the same as that of other elements in the array. Each output from the inverse beamformer is a spatially filtered replica of the signal received by the corresponding array element except for a fixed time delay constant for each element. The same delay is imparted in a second channel to each of the array outputs which are substituted from the corresponding inverse beamformer outputs. If the amplitude and delay of each signal to the subtracter are equal, the outputs from each of the subtracters will no longer contain signal components from the direction of the interfering signal.

Abstract: An improved signal processing technique for developing a plurality of indndent samples, particularly for use in a canceller system receiving interference from a plurality of sources. Each of a plurality of signal channels sample the environment from a plurality of interference source and provide inputs to a configuration of adaptive canceller loops. The loops are connected to provide independent samples of the interference environment from each of the signal channels. In a canceller system, each of the independent loop outputs aree then used as an input to a canceller loop in the main channel to cancel interference in the receiving system. By using the independent samples, a receiving system can significantly increase interference cancellation and reduce the number of recirculations or iterations required.