Abstract: A system for determining the physical path of an object can map several candidate paths to a suitable path space that can be explored using a convex optimization technique. The optimization technique may take advantage of the typical sparsity of the path space and can identify a likely physical path using a function of sensor observation as constraints. A track of an object can also be determined using a track model and a convex optimization technique.

Abstract: According to one aspect of the inventive concept there is provided a transmitter-receiver system comprising: a transmitter arranged to transmit a wavelet; a receiver arranged to receive a wavelet; a wavelet generator arranged to generate a reference wavelet; and timing circuitry arranged to receive a reference clock signal, output a first trigger signal for triggering transmission of a wavelet and output a second trigger signal for triggering generation of a reference wavelet. The timing circuitry further comprises a delay line including at least one delay element and being arranged to receive a signal at an input of the delay line and transmit a delayed signal at an output of the delay line, wherein a state of each delay element of at least a subset of said at least one delay elements is switchable between at least a first state and a second state. A delay element in said first state, i.e. switched to its first state, presents a first propagation delay. A delay element in said second state, i.e.

Abstract: A method of controlling a radar system by receiving a radar return signal from a target and generating a range-Doppler target image signature of the target; selecting a spectral line within the range-Doppler target image signature from a modulation feature on the target which includes an effective point scatterer; providing a range profile for the spectral line; obtaining a reference range profile of a reference point scatterer; determining a difference between a power at a range shorter than a peak corresponding to the modulation feature in the range profile and a power at a corresponding range of the reference range profile; and generating a first control signal or a second control signal arranged to provide or prevent provision of the range-Doppler target image signature based on the difference.

Abstract: A clock data recovery circuit module including a clock recovery circuit, a frequency comparison circuit and a signal detecting circuit is provided. The clock recovery circuit is configured to output a data recovery stream and a data recovery clock based on an input signal and a clock signal. The frequency comparison circuit is coupled to the clock recovery circuit. The frequency comparison circuit is configured to compare a frequency difference between the data recovery clock and the clock signal to adjust the frequency of the clock signal based on a comparison result. The signal detecting circuit is coupled to the frequency comparison circuit. The signal detecting circuit is configured to receive and detect the input signal, and the signal detecting circuit determines whether to enable the frequency comparison circuit according to the detection result. Furthermore, a method for generating a data recovery clock is also provided.

Abstract: The present invention relates to a system (300) for reducing or cancelling unwanted signals when detecting objects of interest with a detection system (200). The detection system thereby is an antenna based system using two or more receive beams as echo response to an emission signal. The system (300) for reducing or cancelling unwanted signals comprises an input means (310) adapted for obtaining from said antenna system (210) receive signals from a first receive beam and receive signals from at least one second receive beam responsive to the same emission signal. It furthermore comprises a coupling means (320) adapted for coupling the receive signals from the first receive beam to the receive signals from the at least one second receive beam, so as to obtain a detection signal for the objects of interest with suppressed unwanted signal contribution.

Abstract: Methods of forming a downlink beam in an adaptive antenna system of a communications system that may reduce inter-system and/or intra-system interference include receiving vectors of signals including signals transmitted by user terminals of the communications system and signals transmitted by transceivers of an independent communications system, obtaining spatial information for the user terminals of the communications system and the transceivers of the independent communications system, generating complex transmitting weights that form spatial nulls directed at the transceivers of the independent communications system, and transmitting a downlink communications signal using the complex transmitting weights. Related systems are also disclosed.

Abstract: Methods and systems consistent with the present invention allow identification of a true signal contained in a signal containing the true signal and noise. In general, digital signal information representing a signal of interest plus noise is utilized by the present invention. The first N samples of digital signal information are stored with the Nth sample being stored in manner which renders it accessible for additional operations. A specially selected set of weights are applied to the buffered N samples and, additionally, phase rotation is applied to the Nth sample. The phase rotated Nth sample and weighted samples are combined using a first equation, described in more detail below. The resulting signal, which exhibits an increased Signal-to-Noise ratio (SNR) and may be more effectively utilized in subsequent MTI processing by virtue of the operations performed on the previous N samples as described herein, is then available for further processing using conventional techniques.

Abstract: A method and system for SNR enhancement in pulse-Doppler coherent target detection for applications in the fields of radar and ultrasound. In accordance with the method of the invention, complex signals are obtained for each of two or more sub-intervals of the time-on-target interval, allowing simultaneous range and Doppler measurements. A coherent integration is the performed on the signals to generate complex-valued folded matrices. The folded matrices are unfolded and target detection is then performed in a process involving one or more of the unfolded matrices. A pulse-Doppler coherent system is also provided configured for target detection by the method of the invention.

Abstract: An apparatus for detecting clutter blocks and an interference source for dynamically establishing a clutter map includes a clutter block detecting module accumulates a plurality of range cell data of each detecting area, and compares the accumulated value with a clutter block level to define the position of a clutter block; a interference source detecting module accumulates all range cell data in each radar beam area, and compares the accumulated value with an interference source reference level to detect whether any interference source exists; and a clutter map establishing module saves the clutter maps on different beam areas in three memory blocks. When one clutter map cell is extracted, the clutter map cells on different beam areas neighboring with the beam area saving extracted clutter map cell are also extracted. The largest value among the extracted clutter map cells is being a clutter threshold value of a detected target.

Abstract: Systems and methods of tracking a beam-aspect target are provided. In embodiments, a target is tracked with a Kalman filter while detections are received. After a detection is missed, the Kalman filter may be concurrently propagated with a blind-zone particle filter until a probability that the target is in a blind zone exceeds a threshold. When the probability exceeds the threshold, the Kalman filter may refrain from further propagating. After a gated detection is received, the blind-zone particle filter and an unrestricted-zone particle filter may be concurrently propagated while a probability that the target is in an unrestricted zone exceeds a threshold. The system may return to tracking with the Kalman filter when a covariance of the unrestricted-zone particle filter falls below a predetermined covariance.

Abstract: The invention concerns a passive radar receiver with an array of antennas for a OFDM received signal comprising frames of symbols each emitted on coded orthogonal carriers. After formatting received signals into digital symbols, dummy signals from dummy OFDM emitters at different distances from and in different directions relative to the receiver are generated and added to the signals picked up by the antennas. The modified received signals are filtered by means of inverse covariance matrices in order to eliminate at least unwanted zero Doppler effect signals and to provide an isotropic reception diagram without blind sector of direct path being generated and by detecting mobile targets along the direct path.

Abstract: Radar systems use time delay measurements between a transmitted signal and its echo to calculate range to a target. Ranges that change with time cause a Doppler offset in phase and frequency of the echo. Consequently, the closing velocity between target and radar can be measured by measuring the Doppler offset of the echo. The closing velocity is also known as radial velocity, or line-of-sight velocity. Doppler frequency is measured in a pulse-Doppler radar as a linear phase shift over a set of radar pulses during some Coherent Processing Interval (CPI). An Interferometric Moving Target Indicator (MTI) radar can be used to measure the tangential velocity component of a moving target. Multiple baselines, along with the conventional radial velocity measurement, allow estimating the true 3-D velocity of a target.

Abstract: A signal separating system 1 comprises a frequency conversion element 3, a dynamic filter component 4 with associated coherent stop slot and non-coherent passband, optionally a signal wave enhancer 7 with bypass, and a frequency reconversion element 8. In operation of the system, mixed incoming signals 12 (CW or pulse signals) having known interference and unknown emission components can be effectively separated, permitting a virtually instantaneous separation of the known interference from the unknown emissions and permitting an unobscured monitoring and/or characterization of the extracted unknown emissions 21, if desired. The arrangement bears definite advantage over known arrangements and retains utility for various frequency/agile or multiple or non-agile unknown signal applications.

Abstract: The invention concerns a passive radar receiver with an array of antennas for a OFDM received signal comprising frames of symbols each emitted on coded orthogonal carriers. After formatting received signals into digital symbols, dummy signals from dummy OFDM emitters at different distances from and in different directions relative to the receiver are generated and added to the signals picked up by the antennas. The modified received signals are filtered by means of inverse covariance matrices in order to eliminate at least unwanted zero Doppler effect signals and to provide an isotropic reception diagram without blind sector of direct path being generated and by detecting mobile targets along the direct path.

Abstract: This invention relates to radar signal processing. In particular, this invention concerns Doppler processing and clutter filtering on irregular Pulse Repetition Time (PRT) sampled signal. This invention solves the above-mentioned drawbacks, in particular solving the velocity ambiguity and filtering any type of clutter, providing a deconvolution method which filter any kind of clutter even varying clutter like sea clutter, rain clutter . . .

Abstract: The present invention provides methods and devices that enable correction of gyroscope bias and gyroscope bias drift in low-cost, vehicular navigation and positioning systems without using estimates of position and heading, and subsequent correction of heading and position errors resulting from gyroscope bias and bias drift, without relying on assumptions regarding gyroscope bias or predetermined time-dependent gyroscope bias drift profiles. The invention improves over existing GPS/DR systems that do not compensate for actual gyroscope bias instability, but instead correct the heading and position error that is induced by the bias instability and then correct estimates of gyroscope bias based on the corrected position and heading. The inventive methods provided herein can be used with any DR vehicle positioning system that uses a gyroscope.

Abstract: A duty dithering method for use with electronic support measures and radar warning receivers, and the like, that provides for improved probability of intercept at low utilization levels. The electronic support measures (ESM) system and radar warning receiver are controlled by a multi-system sensor manager having an ESM scheduler. In accordance with the present method, a maximum duty cycle is chosen for the ESM system. The chosen duty cycle is allocated to the ESM system each frame by the ESM scheduler. At the beginning of each frame, the ESM scheduler picks a random offset and subtracts it from the maximum duty to compute an ESM duty for that frame. The ESM scheduler commands data collections based on the computed duty for that frame. This step is repeated each frame.

Abstract: Coherent bursts of N wideband, low repetition frequency width-modulated pulses are transmitted, and they are received with pulse compression and then sampling. For each range gate and each speed hypothesis, a selection is made of the corresponding samples of N repetitions of a burst after compensation for the migration in distance. On each set of N samples, for a given speed hypothesis, a Fourier transform and a threshold-setting operation are performed. The distance and the unambiguous speed of the detected targets are then extracted.

Abstract: A moving target indicating system wherein a pulse source which generates radiofrequency drive pulses at a predetermined pulse repetition frequency is connected to the inputs of a pair of channels. The first channel includes a phase-dispersive filter having a first phase-slope dispersion characteristic, while the second channel has a phase-dispersive filter having a phase-slope dispersion characteristic which is the negative of that of the first filter. A pulse group comprising the output of the first and the second channels is transmitted periodically as each drive pulse is applied. The pulse repetition frequency is sufficiently low that when transmitted, echos of only one pulse of each group are received at a time.

Abstract: An ADPCA subsystem includes a weight processor for weighting the delta channel signal according to the results of an adaptive algorithm to which the output of a DPCA vector combiner is input. An AMTI vector combiner is connected to the output of the DPCA vector combiner to form the filter output. The delta channel signal is time delayed and samples of the delta channel signal are collected by the processor together with a sum channel sample and a residue sample, in order to apply the proper weights to the undelayed and delayed delta channel samples. The output of the ADPCA weight processor therefore provides an optimum correction signal to the vector combiner.

Abstract: In a method for the detection, localization and velocity determination of moving targets from raw radar data from a coherent, single- or multi-channel image system (SAR), for representing the surface of the earth with different backscatter ratios, chronologically successive azimuth spectra are continuously formed during a defined period of time and a frequency shift of the backscatter ratio portion is obtained by determining the position of the maximum of the correlations between respectively two azimuth spectra formed chronologically directly in succession. Then the frequency shifts of the entire raw radar data set are evaluated for producing a frequency shift map.By searching for values deviating from the nominal Doppler rate in the Doppler rate map, a respective moving target is detected and the center of an image of the detected moving target is formed from this.

Abstract: An MTI radar based on a comparison of the Doppler shifts of the original signal and a phase-reversed signal using pulse compression wherein the received signal is phase detected for in-phase and quadrature components relative to the IF. A Doppler-corrected pulse compressor produces a magnitude signal for the Doppler shift of the received signal from the sequence of in-phase and quadrature components. Another Doppler-corrected pulse compressor produces a magnitude signal for the Doppler shift of the received signal from the conjugates of the sequence of in-phase and quadrature components. The magnitude signal of the same Doppler shift of the two compressors are compared and the difference is the output of the MTI.

Abstract: A radar system comprises a transmitter which essentially continuously transmits a modulated carrier wave signal and a receiver for receiving the carrier wave signal reflected at an object (echo signal). The carrier wave signal is modulated with a code-generating signal whose code frequency is determined for the range resolution of the radar. The code-generating signal is such that one bit in the code has a duration which is several times longer than the period of the carrier wave signal and several bits of the code form a block which is obtained by modulation of a carrier wave with constant frequency. The frequency of the carrier wave is changed between blocks so that the transmitter sends a block with a carrier wave frequency which is different from the carrier wave frequency or frequencies which the receiver is set up to receive. The receiver stores the transmitted code and correlates it with the received signal.

Abstract: In a doppler radar, in order to compensate for the speed of moving clutter, one first establishes during a burst of order (i) the phase variation .phi.r.sub.i from one period to the next and which is due to clutter in a given range cell. Then, this phase variation .phi.r.sub.i is memorized and is used during the course of each of the periods of repetition of the next burst to modify the phase of the signal received from the clutter from the same range cell in a maner as to displace its Doppler frequency towards the zero frequencies band, and band which corresponds to the rejection zone of the fixed echoes eliminating filter.

Abstract: A device for removing ambiguities in the range and speed at the output of a Doppler-type radar in which all possible sets (p.sub.1, q.sub.1) and (p.sub.2, q.sub.2) corresponding to echoes at different repetition frequencies are stored in a first memory, p.sub.1 and p.sub.2 representing the number of the range quantum from which an echo signal is received and q.sub.1 and q.sub.2 the number of the filter at the output of which an echo signal is maximum. Pairs of signals are supplied in response to a first clock signal together with radar data in a second memory to two calculating circuits which carry out tests to determine of p.sub.1 and p.sub.2 and q.sub.1 and q.sub.2 respectively come from the same target and calculate the true target distance and true Doppler frequency. If both tests are positive the true distance and frequency are stored in a memory. If either is negative the first clock signal is produced to supply a new pair to the respective calculating circuits.

Abstract: The present invention provides a system that cancels second time around clutter in a multiple pulse repetition frequency radar system which uses three groups of differently spaced pulses. The system processes returns from a clutter cancellation group of eight pulses from three different concatenated pulse repetition frequency groups, using two pulses from one group, all pulses from a central group and two pulses from a third group. The pulse returns are each multiplied by a different weight and the eight weighted returns are added together and output as the filtered return signal. As the weights of the outer pairs of pulses increase, as compared to the weights of the inner four pulses, the second time around clutter cancellation effects increase and the first time around clutter cancellation effects decrease.

Abstract: A moving target indicator device comprising a first clutter removing circuit for responding to a radar having a variable transmit repetition time and for removing clutter having a Doppler speed of nearly zero from a radar received signal having stationary clutter and moving clutter. The device further includes a correction circuit to keep the amplitude components and the phase components of the first clutter removing circuit output substantially constant. A second clutter removing circuit removes clutter having a constant amplitude component and phase component from the output of the correction circuit.

Abstract: A pulse doppler radar having variable repetition rates, noise pulses resulting from echos received from stationary multiple-time-around objects are removed by subjecting the reflected pulses to a coherent integration modified by means of a simplified vectorial addition of the reflected pulses, using an integration circuit consisting of a plurality of filters.The signal amplitude produced at the output of each filter is individually compared to the mean value of signals produced by all other filters, and a target indication is produced when the mean value is exceeded by the amplitude of a signal from an individual filter.