Abstract: A system and method for concurrently operating a plurality of agile beam radar modes by pulse-to-pulse interleaving groups of the radar modes. Radar modes are grouped, each radar mode being allocated a certain amount of time for operation and a suitable pulse repetition frequency to improve or optimize the duty cycle of the antenna while concurrently operating the plurality of modes. Priorities may be assigned to groups or to individual radar modes within each group. In some embodiments, TDM communications are further interleaved within the radar modes to enhance the operation of the radar antenna.

Abstract: A LADAR system for coherently imaging a target within a volume has a modulated laser transmitter at a frequency and a receiver. The receiver has a plurality of lenses, each with its own detector. Each detector is supplied by a centrally located local oscillator tuned to the frequency. The paths from the local oscillator to each detector, as well as the delay within each lens/detector combination are measured during a calibration. A calibrating reflector reflects a test signal during the calibration at many frequencies, temperatures and accelerations. Measurements of paths and delays obtained during the calibration are stored, and used to phase compensate subsequent target reflections for coherent processing.

Abstract: A system and method for concurrently operating a plurality of agile beam radar modes by pulse-to-pulse interleaving groups of the radar modes. Radar modes are grouped, each radar mode being allocated a certain amount of time for operation and a suitable pulse repetition frequency to improve or optimize the duty cycle of the antenna while concurrently operating the plurality of modes. Priorities may be assigned to groups or to individual radar modes within each group. In some embodiments, TDM communications are further interleaved within the radar modes to enhance the operation of the radar antenna.

Abstract: A hovering helicopter has a radar transmitter/receiver for transmitting radar pulses for illuminating a target for SAR imaging, and rotor blades for generating lift. Radar reflectors are on the rotor blades. The radar reflectors are oriented to reflect the radar pulses from the transmitter to the target as the rotor blades rotate. The radar pulses reflected by the moving reflector from the transmitter are timed to generate the synthetic aperture image using radar returns from the target. The receiver also receives blade returns directly reflected from the moving reflectors attached to the lift rotor blades. The receiver analyzes the blade returns to extract motion details of the reflectors and uses the motion details for motion compensation of target returns for SAR imaging.

Abstract: A LADAR system for coherently imaging a target within a volume has a modulated laser transmitter at a frequency and a receiver. The receiver has a plurality of lenses, each with its own detector. Each detector is supplied by a centrally located local oscillator tuned to the frequency. The paths from the local oscillator to each detector, as well as the delay within each lens/detector combination are measured during a calibration. A calibrating reflector reflects a test signal during the calibration at many frequencies, temperatures and accelerations. Measurements of paths and delays obtained during the calibration are stored, and used to phase compensate subsequent target reflections for coherent processing.

Abstract: A hovering helicopter has a radar transmitter/receiver for transmitting radar pulses for illuminating a target for SAR imaging, and rotor blades for generating lift. Radar reflectors are on the rotor blades. The radar reflectors are oriented to reflect the radar pulses from the transmitter to the target as the rotor blades rotate. The radar pulses reflected by the moving reflector from the transmitter are timed to generate the synthetic aperture image using radar returns from the target. The receiver also receives blade returns directly reflected from the moving reflectors attached to the lift rotor blades. The receiver analyzes the blade returns to extract motion details of the reflectors and uses the motion details for motion compensation of target returns for SAR imaging.

Abstract: A system for scanning an antenna array of the present invention. The system includes a first mechanism for modulating a desired signal on an optical carrier signal. The first mechanism includes a frequency-tunable optical oscillator with a phase shifter for changing an output frequency of the optical oscillator. A second mechanism employs the optical carrier signal to derive signals having predetermined phase relationships. A third mechanism receives the feed signals and radiates corresponding transmit signals in response thereto to the antenna array to steer the array. In more specific embodiment, the desired signal is a Radio Frequency (RF) signal, and the phase shifter is an electrically controlled optical RF phase shifter. The optical carrier signal includes a first optical carrier signal and a second optical carrier signal.

Abstract: A system for scanning an antenna array of the present invention. The system includes a first mechanism for modulating a desired signal on an optical carrier signal. The first mechanism includes a frequency-tunable optical oscillator with a phase shifter for changing an output frequency of the optical oscillator. A second mechanism employs the optical carrier signal to derive signals having predetermined phase relationships. A third mechanism receives the feed signals and radiates corresponding transmit signals in response thereto to the antenna array to steer the array. In more specific embodiment, the desired signal is a Radio Frequency (RF) signal, and the phase shifter is an electrically controlled optical RF phase shifter. The optical carrier signal includes a first optical carrier signal and a second optical carrier signal.

Abstract: A radar transmitter is at a first location on a moving platform and illuminates a target with a sequence of frequency modulated radar pulses. The frequency modulated pulses are linear frequency modulated, i.e. chirped. The target reflects the frequency modulated radar pulses. A receiving antenna has a difference pattern null and receives the reflections from the target as a main scatterer and an ambiguity of the main scatterer. The sequence of pulses change the start of their frequency modulation (chirp) over a SAR array. The change in start frequency from pulse to pulse allows to shift the range ambiguity so as to align with the delay/Doppler difference pattern null of the antenna. Thus, both the main scatterer as well as the shifted range ambiguity are on the difference pattern null, facilitating their cancellation.

Abstract: A radar antenna has a reflector and maximum gain along its boresight. The reflector has a periphery, typically circular, rectangular or elliptical. A plurality of Global Positioning System (GPS) satellite signal receiving antennas are rigidly, mechanically attached to the reflector near its periphery. The plurality of GPS satellite signal receiving antennas are connected pairwise to a phase comparator for comparing a plurality of first phase differences induced by a first GPS satellite signal received concurrently between the plurality of GPS satellite signal receiving antennas. A Phase comparator measures the phase difference of the signal received at GPS satellite signal receiving antennas pairwise thus performing a differential phase measurement. This differential phase measurement is supplied to a computer for identifying an ambiguous boresight position using the phase differences measured by the phase comparator. The position of the GPS satellites is known with respect to the geo-location of the antenna.

Abstract: An antenna array includes an upper conductive plate structure comprising a lattice array of holes to form a radiating aperture. A lower conductive plate structure is disposed in a spaced relationship relative to the upper plate structure. The lower plate structure has an upper surface whose spacing from a lower surface of the upper plate varies in a first direction parallel to the lower surface. The array includes relative rotation apparatus for imparting relative rotational movement between the upper plate structure and the lower plate structure.

Abstract: A radar on a moving platform for three dimensional target recognition of a target on a flat or sloping terrain is described. The target is illuminated from a plurality of locations to generate images at many aspect angles. The radar is positioned at a low grazing angle with respect to the target for generating a shadow of the target on the flat or sloping terrain for each aspect angle of the plurality of aspect angles. The radar comprises an analog to digital converter for converting reflections from the target induced by radar illumination into target digital data and for converting reflections induced by the illumination from the flat or sloping terrain into terrain digital data.

Abstract: A radar system (500) radiates a radar transmit signal, has a radar signal receiver (503) and a canceller (505) for canceling leakage of the transmit signal into the radar signal receiver (503). The canceller (505) comprises a digital waveform generator (528) for generating a first digital signal converted to an analog waveform. The analog waveform is amplified after a fixed delay (534) to generate a first cancellation signal input into a circulator (504). The circulator combines the first cancellation signal with the leakage to generate a first corrected signal. A summer (507) combines the first corrected signal from the circulator with a second cancellation signal to generate a second corrected signal. The second cancellation signal is generated by a digital cancellation filter (526). The digital cancellation filter (526) has as an input the first digital signal from the digital waveform generator (528).

Abstract: Detection of moving targets in SAR images is improved by a radar on a moving platform for generating a focused synthetic aperture image of a scene The scene contains a target described by pixels within the SAR image. The radar has a monopulse antenna having a sum channel output and a difference channel output feeding analog to digital converters for converting the sum channel output and difference channel output into respective digital streams concurrently. The digital streams generate a difference channel SAR image and a sum channel SAR image. Target ratios are computed for those pixels descriptive of a target within the scene. Background ratios are computed for pixels around the target. Target ratios and background ratios define respective least square fit of angle discriminants. Comparing the target least square fit of angle discriminant with the background least square fit angle discriminant identifies an angle offset and a Doppler offset of the target with respect to the background.

Abstract: A guidance system for guiding each of several projectiles toward a moving target has a platform having a radar system for illuminating the target with a radar signal. Each projectile has a receiver for receiving the radar signal reflected from the target, a transponder for replying to Global Positioning System (GPS) like timing signals from several timing signal sources, and a data link transceiver for establishing a bidirectional data link to the platform. The data link carries the measured frequency shift of the radar signal reflected from the target as measured by the projectile. A computer on the platform computes a relative position of each projectile with respect to the target from tracking the moving target using the radar system and the reply signal from the transponder on each projectile. The data link sends guidance commands from the platform to each projectile to guide the projectile to the target.

Abstract: A radar receiver on a moving platform images a moving target and non-moving clutter using a single SAR array. The radar receiver converts the radar returns into digital radar returns and motion compensates the digital radar returns with respect to a reference, then applies further phase compensation to obtain an autofocused synthetic aperture image. A plurality of moving target pixels descriptive of the moving target are detected within the autofocused synthetic aperture image. The plurality of moving target pixels are transformed from the autofocused image to the time domain. The time domain moving target data is focused by iteratively applying a phase compensation to the time domain moving target data.

Abstract: A target is detected under a forest canopy or other elevated clutter where the target is obscured by the elevated clutter. Radar returns reflected from the target on the surface, combined with those from the elevated clutter are digitized. Motion compensation is performed for the radar returns with respect to the target to obtain a focused first synthetic aperture image of the target. Next, the radar returns are motion compensated with respect to the elevated clutter at various heights above the surface to obtain images of the elevated clutter. The elevated clutter within the images at the various heights above the surface is identified and coherently subtracted from the original synthetic aperture images.

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: A millimeter wave (MMW) antenna array includes a continuous transverse stub (CTS) radiating aperture comprising a set of spaced continuous transverse stubs, each having a longitudinal extent. A series feed system is coupled to an excitation source for exciting the stubs with MMW electromagnetic energy having a linear phase progression along the longitudinal extent of the stubs to produce an array beam which can be scanned over a beam scan range by changing the excitation frequency.

Abstract: A Synthetic Aperture Radar (SAR) avoids the need for an INS/GPS by focusing a SAR image having discernible features and a center. The image is formed from digitized returns, each of the digitized returns having a phase and an amplitude. The focusing steps of an algorithm processing the digitized returns include: computing a coarse range and coarse range rate of the center of the image, motion compensating the digitized returns, converting the digitized returns in polar format into an orthogonal Cartesian coordinate system, autofocusing the image data to obtain a focused image, performing a Fourier transform to obtain a focused image described by the returns, computing an estimated fine range and fine range rate from features contained within the focused image, and converging the fine range and fine range rate within the orthogonal Cartesian coordinate system for use within the azimuth and range coordinate system and motion compensating the digitized returns.