Abstract: Target detection in the presence of non stationary clutter is improved by a radar receiver on a moving platform for detecting a target using a plurality of short coherent arrays and a plurality of long coherent arrays synthesized from the short coherent arrays overlapping the target. The target is obscured by slow scale clutter and fast scale clutter in the vicinity of the target.

Abstract: A radar system derives a correction for an actual boresight (311) of a radar monopulse antenna mounted on a moving platform from ? data and ? data generated with respect to an a priori known, calibrated boresight (309). The monopulse antenna (602) is coupled to a ground position measuring system (616) while acquiring data. The radar receiver acquires a ? and ? synthetic aperture map of the same radar scattering location with respect to the calibrated boresight. ? SAR data and the ? SAR data are motion compensated using the position and velocity supplied by the ground positioning system. A computer forms a ratio of the aligned ? pixels to the aligned ? pixels for each of a plurality of aligned ? pixels located near the calibrated boresight. The correction for the location of the actual boresight of the monopulse antenna is computed by an analysis of the ratio of aligned ? pixels and corresponding aligned ? pixels over the radar scattering location.

Abstract: An efficient digital wideband waveform generation and signal processing system for multi-beam electronically scanned antenna array (ESA) radar systems. The digital waveform generator (50) first produces a series of waveform phase angles corresponding to the phase angles of a common signal to be transmitted by the ESA. Then, for each antenna element, the waveform phase angles are adjusted to steer the beam by adding a time delay and a phase adjustment. A digital signal is then produced for each antenna element by applying a cosine function to the adjusted phase angles. In the illustrative embodiment, this is accomplished using a cosine look-up table (14). Each digital cosine wave is then stored in a serial memory buffer (16A to 16L) in preparation for conversion to digital. Each of digital signals is passed through a digital to analog converter (18A to 18L) and an RF filter (20A to 20L) at each antenna element.

Abstract: An interferometer array system and method for processing pulse signals from a target emitter includes an n element interferometer array of radiator elements for producing radiator signals in response to the pulse signals from the target emitter. M processing channels process radiator signal elements, where m<n. A switch matrix is connected between the array and the processing channels, switching different combinations of the radiator elements to the channels within a single pulse to achieve processing of all radiator signals within a single pulse of said pulse signals from the target emitter.

Abstract: An interferometer array system for processing pulse signals from a target emitter includes an n element interferometer array of radiator elements for producing radiator signals in response to the pulse signals from the target emitter. M processing channels process radiator signal elements, where m<n. A switch matrix is connected between the array and the processing channels, switching different combinations of the radiator elements to the channels within a single pulse to achieve processing of all radiator signals within a single pulse of said pulse signals from the target emitter.

Abstract: The height of a radar target above a horizontal plane at a location within the horizontal plane is measured using a synthetic aperture radar (SAR). The synthetic aperture radar is mounted on a moving platform. The moving platform moves along a continuous climbing path with respect to the horizontal plane acquiring a plurality of SAR arrays of radar return information. Monopulse , Interferometric SAR (IF-SAR), and shadow length height measurements are fused to refine the target height measurement. Monopulse and IFSAR are combined to resolve target height ambiguities. The SAR arrays are separated vertically, at separate heights with respect to the target, and acquired sequentially in time, as a single pass.

Abstract: A the system for scanning an antenna array (26) adapted for use with active radar arrays. A first mechanism (14, 18, 20, 24) generates an optical signal oscillating at a predetermined frequency. A second mechanism (32, 34) employs the optical signal to derive feed signals, which have predetermined phase relationships. A third mechanism (22) receives the feed signals and radiates corresponding transmit signals in response thereto to the antenna array (26) to steer the antenna array (26) in accordance with the predetermined phase relationships. In a specific embodiment, the transmit signals are microwave frequency signals. The first mechanism (14, 18, 20, 24) includes a first optical oscillator (18) and a second optical oscillator (20) that feed a first optical manifold (32) and a second optical manifold (34), respectively, of the second mechanism (32, 34).

Abstract: An imaging system and method. The invention provides an intra-pulse repetition interval (PRI) agile beam technique for enhanced resolution that can be used at aspect angles near the velocity vector of a host vehicle. It is particularly useful at small scan angles where beam sharpening array times become large. At these scan angles, the bandwidth of the clutter is narrower than at higher scan angles and allows large PRIs without degradation from Doppler ambiguities. In accordance with the present teachings, sequential illumination is performed within a PRI to multiple beam locations using an agile beam. The interleaving of beams reduces map formation times compared to conventional techniques using sequential arrays. The inventive system is adapted for use with an electronically scanned (e.g., synthetic aperture array radar) antenna.

Abstract: A system and method (32) for measuring line-of-sight angular rates for all-weather precision guidance of distributed projectiles (16) and a guidance system (10) based thereon. In accordance with the novel method (32) for measuring line-of-sight angular rates, first the range rates of the target (14) relative to at least two projectiles (16) is determined, as well as the position and velocity of each projectile (16). Then, the line-of-sight angular rate of the target (14) relative to at least one projectile (16) is computed from the range rates, positions, and velocities. In the illustrative embodiment, the range rate of the target (14) relative to a projectile (16) is determined based on a monostatic target Doppler measurement, a monostatic projectile Doppler measurement, a bistatic Doppler measurement of the target (14) by the projectile (16), and the carrier frequency of a data link (26) between the projectile and the shipboard system.

Abstract: A method for exciting an antenna with a waveform having a burst width and pulse width scaled proportionately with a selected range scale and a temporal filter to address any ambiguities in range resulting from the transmission of a signal in accordance with the novel waveform. The inventive filtering method includes the step of scanning a beam including a plurality of pulses of electromagnetic energy. The step of scanning the beam includes the step of outputting a beam excited by a waveform having a burst width and pulse width scaled proportionately with a selected range scale. Reflections of these pulses are received as return signals. The returns are processed to extract range in range rate measurements. The range and range rate measurements are compressed to form a plurality of range bins. The pulses are selectively weighted to reduce sidelobes resulting from a subsequent Fast Fourier transform (FFT) operation.

Abstract: An imaging system and method. The invention provides an intra-pulse repetition interval (PRI) agile beam technique for enhanced resolution that can be used at aspect angles near the velocity vector of a host vehicle. It is particularly useful at small scan angles where beam sharpening array times become large. At these scan angles, the bandwidth of the clutter is narrower than at higher scan angles and allows large PRIs without degradation from Doppler ambiguities. In accordance with the present teachings, sequential illumination is performed within a PRI to multiple beam locations using an agile beam. The interleaving of beams reduces map formation times compared to conventional techniques using sequential arrays. The inventive system is adapted for use with an electronically scanned (e.g., synthetic aperture array radar) antenna.

Abstract: A system and method (32) for measuring line-of-sight angular rates for all-weather precision guidance of distributed projectiles (16) and a guidance system (10) based thereon. In accordance with the novel method (32) for measuring line-of-sight angular rates, first the range rates of the target (14) relative to at least two projectiles (16) is determined, as well as the position and velocity of each projectile (16). Then, the line-of-sight angular rate of the target (14) relative to at least one projectile (16) is computed from the range rates, positions, and velocities. In the illustrative embodiment, the range rate of the target (14) relative to a projectile (16) is determined based on a monostatic target Doppler measurement, a monostatic projectile Doppler measurement, a bistatic Doppler measurement of the target (14) by the projectile (16), and the carrier frequency of a data link (26) between the projectile and the shipboard system.

Abstract: A system for locating the position of an emitter emitting a signal having time domain features is described. At least two platforms are used. Both have a receiver for detecting the emitter signal, an FFT channelizer to act as a bandpass filter for extracting the time domain features from the emitter signal, and a thresholder for thresholding the time domain signal. An FFT transform and a correlator using templates further extract frequency domain markers identifying the emitter. The frequency domain markers identifying the emitter are transmitted between platforms using a wireless link increasing the probability of detection of the emitter at all platforms.

Abstract: A recirculating delay line that includes an optical delay circuit generates repetitions of an input signal waveform that is of limited time duration.

Abstract: An efficient digital wideband waveform generation and signal processing system for multi-beam electronically scanned antenna array (ESA) radar systems. The digital waveform generator (50) first produces a series of waveform phase angles corresponding to the phase angles of a common signal to be transmitted by the ESA. Then, for each antenna element, the waveform phase angles are adjusted to steer the beam by adding a time delay and a phase adjustment. A digital signal is then produced for each antenna element by applying a cosine function to the adjusted phase angles. In the illustrative embodiment, this is accomplished using a cosine look-up table (14). Each digital cosine wave is then stored in a serial memory buffer (16A to 16L) in preparation for conversion to digital. Each of digital signals is passed through a digital to analog converter (18A to 18L) and an RF filter (20A to 20L) at each antenna element.

Abstract: A system for locating the position of an emitter emitting a signal having time domain features is described. At least two platforms are used. Both have a receiver for detecting the emitter signal, an FFT channelizer to act as a bandpass filter for extracting the time domain features from the emitter signal, and a thresholder for thresholding the time domain signal. An FFT transform and a correlator using templates further extract frequency domain markers identifying the emitter.

Abstract: A method for exciting an antenna with a waveform having a burst width and pulse width scaled proportionately with a selected range scale and a temporal filter to address any ambiguities in range resulting from the transmission of a signal in accordance with the novel waveform. The inventive filtering method includes the step of scanning a beam including a plurality of pulses of electromagnetic energy. The step of scanning the beam includes the step of outputting a beam excited by a waveform having a burst width and pulse width scaled proportionately with a selected range scale. Reflections of these pulses are received as return signals. The returns are processed to extract range in range rate measurements. The range and range rate measurements are compressed to form a plurality of range bins. The pulses are selectively weighted to reduce sidelobes resulting from a subsequent Fast Fourier transform (FFT) operation.

Abstract: An imaging processing system and method. In accordance with the invention, the illustrative method includes the steps of providing a transfer function between scene excitations and voltage returns based on geometry, beam pattern and/or scan rate; ascertaining a set of scene excitations that minimize a penalty function of the transfer function; and ascertaining a set of scene intensities based on the scene excitations, and a set of optimal weights for the penalty function based on the scene reflectivities. The inventive method provides significantly enhanced image sharpening. In the illustrative embodiment, the inventive method uses an iterative convergence technique which minimizes a penalty function of the sum of square errors between the scene excitations corrupted by the radar system (i.e. the antenna pattern and processing) and the radar voltage returns.

Abstract: A substantially lossless transmissive link, such as an RF fiber optic link, that selectively employs a number of techniques to improve various link parameters. The link may be structured to comprise a high power light source, such as a laser, that provides light output having a high level of optical power. A feedback circuit may be disposed around the light source that reduces relative-intensity-noise levels produced by the light source at low frequencies. A modulator is provided that modulates the light output of the light source. Preferably, a dual output modulator may be used to provide two modulated optical signals whose respective RF modulation is “effectively” 180 degrees out of phase. An optical fiber that transmits the modulated optical signal(s). A photodetector without a load resistor directly on its output that is operable at the high level of optical power, receives the modulated light and recovers the RF signal.

Abstract: A processing method for use in providing improved SAR imagery at high duty factors that provides for enhanced radar sensitivity. Radar signals are transmitted that embody a high duty factor ultra-high resolution SAR waveform generated using a biphase code with a predetermined high pulse compression ratio. Received radar returns comprising a SAR map are Fourier transformed and multiplied by a stored set of complex weights. The resultant Fourier transformed complex weighted SAR map is then inverse Fourier transformed to obtain compressed range bins. The inverse Fourier transformed SAR map is then processed for display.