Abstract: Aspects of the disclosure are directed to spatial imaging using an imaging radar including generating a plurality of range/Doppler/channel images from a detected image and a four-dimensional image; generating a transfer matrix for each of the plurality of range/Doppler/channel images; generating a plurality of scatterer parameters using maximum likelihood (ML) processing on the plurality of range/Doppler/channel images; generating a plurality of refined scatterer parameters from the plurality of scatterer parameters and the transfer matrix; determining a minimal-order scatterer configuration using the plurality of refined scatterer parameters and the transfer matrix; and generating a set of determined scatterer parameters from the minimal-order scatterer configuration and the transfer matrix.

Abstract: Aspects of the disclosure are directed to spatial imaging using an imaging radar including generating a plurality of range/Doppler/channel images from a detected image and a four-dimensional image; generating a transfer matrix for each of the plurality of range/Doppler/channel images; generating a plurality of scatterer parameters using maximum likelihood (ML) processing on the plurality of range/Doppler/channel images; generating a plurality of refined scatterer parameters from the plurality of scatterer parameters and the transfer matrix; determining a minimal-order scatterer configuration using the plurality of refined scatterer parameters and the transfer matrix; and generating a set of determined scatterer parameters from the minimal-order scatterer configuration and the transfer matrix.

Abstract: A method and apparatus for sampling a high bandwidth analog signal includes: splitting the high bandwidth analog signal into N parallel channels; randomly demodulating each of the signals; sampling each demodulated signal using a sub-Nyquist sampling rate; combining each sampled signal into a sub-Nyquist signal; compressive sensing the combined sub-Nyquist signal to estimate missing samples of a full Nyquist rate uniform sample set X(n); convolving X(n) with N analysis filters, each analysis filter having a different coefficient; decimating output of each analysis filter using decimation ratios of M:1 to generate a sub-banded signal set Yi (n), i=1, . . . , N; processing the sub-banded signal set; up-sampling each processed sub-band signal by M; convolving each up-sampled sub-band signal with a corresponding synthesis filter; and combining two or more of the convolved signals to generate a non-uniform spectral partitioning of the high bandwidth analog signal.

Abstract: System and method for converting a high bandwidth analog signal to a digital signal including: receiving the high bandwidth analog signal; splitting the high bandwidth analog signal to M parallel channels; delaying the split signal in each channel with N*T delays, respectively; sampling each M delayed signals by M relatively prime sampling rate, wherein the sampling rate for each M delayed signal is smaller than the Nyquist frequency of the high bandwidth analog signal; upsampling each M sampled signal, wherein the upsampling rate for each M sampled signal satisfies the Nyquist frequency of the high bandwidth analog signal; combining the M up sampled signals into a combined signal; and reconstructing the combined signal to generate a digital signal representing the high bandwidth analog signal.

Abstract: System and method for converting a high bandwidth analog signal to a digital signal including: receiving the high bandwidth analog signal; splitting the high bandwidth analog signal to M parallel channels; delaying the split signal in each channel with N*T delays, respectively; sampling each M delayed signals by M relatively prime sampling rate, wherein the sampling rate for each M delayed signal is smaller than the Nyquist frequency of the high bandwidth analog signal; upsampling each M sampled signal, wherein the upsampling rate for each M sampled signal satisfies the Nyquist frequency of the high bandwidth analog signal; combining the M up sampled signals into a combined signal; and reconstructing the combined signal to generate a digital signal representing the high bandwidth analog signal.

Abstract: A synthetic aperture radar (SAR) image of a wide coverage area is acquired during a frame containing a first plurality of ambiguities induced in the SAR image from radar scatterers within the area. The area is illuminated with radar pulses and a segmented receive antenna oriented towards the area. The segmented receive antenna has a second plurality of sub-apertures, where the second plurality of sub-apertures is larger than the first plurality of ambiguities. Each sub-aperture has its own receiver. The digital stream from each receiver is stored in a computer for the duration of the frame to obtain frame data. A SAR image is extracted from the frame data. The first plurality of ambiguities are identified from analysis of the frame data, and a correction is computed to account for the first plurality of ambiguities contained within the synthetic aperture image. The correction is applied to reduce distortions caused by the ambiguities in the SAR image.

Abstract: A system and technique for phased array antenna beam steering for transmitting and receiving without sending the waveform through an actual (physical) time delay when a time varying frequency is used as the waveform. The inventive system is adapted for use with an antenna having an array of radiating elements and includes a plurality of signal sources. Each source is adapted to provide a signal having a predetermined frequency offset signal for an associated radiating element or set of radiating elements. For transmit a plurality of first mixers is provided. Each of the first mixers is coupled to receive an excitation signal as a first input and the output from a respective one of the sources as a second input. The output of each mixer is coupled to a respective subset of the antenna radiating elements. In effect, each of the sources provides a virtual time delay.

Abstract: A system and technique for phased array antenna beam steering for transmitting and receiving without sending the waveform through an actual (physical) time delay when a time varying frequency is used as the waveform. The inventive system is adapted for use with an antenna having an array of radiating elements and includes a plurality of signal sources. Each source is adapted to provide a signal having a predetermined frequency offset signal for an associated radiating element or set of radiating elements. For transmit a plurality of first mixers is provided. Each of the first mixers is coupled to receive an excitation signal as a first input and the output from a respective one of the sources as a second input. The output of each mixer is coupled to a respective subset of the antenna radiating elements. In effect, each of the sources provides a virtual time delay.

Abstract: An adaptive signal processor (100) utilized with a receiving system (10) in a non-stationary environment having a receiver element (12) for receiving a composite signal comprised of a desire input signal and an interference signal. The invention includes a first mechanism (102) for modulating the composite signal to provide a plurality of modulated signals and to generate a plurality of synthetic channels (104). A second mechanism (126) is provided for calculating and applying a plurality of adaptive weight values to the modulated signals in the synthetic channels (104) to provide a plurality of time varying weighted signals. Finally, a third mechanism (128) is provided for combining the time varying weighted signals in the synthetic channels (104) to eliminate the interference signal from the composite signal. In a preferred embodiment, the composite signal is received by an antenna or hydrophone (12) and then digitized and stored in a memory (122).

Abstract: A maximum likelihood estimator and range-only-initialization target detection method employed to detect and resolve targets in a multislope linear frequency modulated waveform radar. The method resolves a large number of target returns without a large amount of signal processing and without creating a significant number of false alarms, or ghosts. The method simultaneously estimates range and doppler for each target. The method rejects undesired long-range targets that fold into target regions, and processes target regions of interest around a nearest target to reduce signal processing throughput requirements. Using a K out of N detection rule, the method detects targets that compete with mainlobe rain clutter, mainlobe ground clutter, and receiver leakage. The method simultaneously estimates target parameters and optimally resolves any number of targets.