Abstract: A bistatic coherent unlocked radar system and processing method using an advanced waveform that permits bistatic unlocked coherent operation of an unlocked radar transmitter and receiver. The waveform implements intrapulse fine range resolution, pulse to pulse coherency and burst to burst frequency agility to provide for enhanced target detection and robust operation in electronic countermeasure environments. A continuous sequence of pulses at different frequencies is transmitted that may contain an acquisition frequency that is revisited) more times than the other frequencies. Energy reflected from a target is processed to detect energy at the acquisition frequency, for example, over a plurality of range bins and predetermined pulse repetition intervals. A range pattern is generated if the detected energy is above a predetermined threshold. The energy is centroided to indicate the relative angle to the target. The transmitted frequencies contained in the pattern of energy are identified.

Abstract: Methods that compensate for phase errors caused by path length variations in a radar system, and that compensate for relative phase errors in upconvertor and downconverter references employed in the radar system. One method samples a signal reflected from a duplexer through a receiver during the time the radar pulse is transmitted. The signal reflected from the duplexer is compared to a radar echo pulse on a single pulse basis. The phase of the sampled signal is subtracted from the phase of the received radar echo pulse reflected to determine the phase error. In a second method, multiple samples are collected during the time each radar pulse is transmitted. Samples of the signal reflected from the duplexer and the radar echo pulse are compared on a pulse to pulse basis. The phase differences are averaged across the pulse duration. The averaged phase differences are integrated on a pulse to pulse basis to determine the phase error.

Abstract: Fiber optic delay lines in the form of a modified corporate feed having progressive phase delays and a corporate feed having equal phase delays are used to couple RF modulated light signals to detecting, mixing, amplifying and radiating devices of an active array radar. Different RF signals may be sent over the same fiber delay lines using different light colors (or wavelengths) so that the RF modulated signals in the fiber delay lines do not interact with each other. The RF signals can be put on and taken out of the fiber lines using wavelength division multiplexers, for example. This provides an array with a single optical manifold that allows simultaneous full aperture operation at multiple frequencies and/or beams over a wide operating frequency range.

Abstract: A data processing method for use in processing synthetic array radar data to more accurately steer its antenna toward a target. A radar signal is transmitted, and sum and difference channel synthetic array radar maps derived from the transmitted radar signal are formed. A target cell within the synthetic array radar maps is designated, and a window surrounding the target cell is defined. Discriminant values for each of the cells within the window are computed that comprise the difference channel value divided by the sum channel value for each cell. A best fit line through the computed discriminant values is then computed. A null cell where the discriminant value defined by the best fit line is equal to zero is determined. Then, the radar signal is steered so that the null cell coincides with the designated target cell.

Abstract: A method of processing radar returns derived from a new radar waveform. The method processes radar returns derived from transmitting the radar waveform to provide simultaneous matched processing and range profiling of different size objects in the presence of clutter. In the present method, radar returns are digitized and processed to produce pulse compressed radar returns having a predetermined (169:1) pulse compression ratio. A pulse to pulse fast Fourier transform on each RF step is performed on the pulse compressed radar returns. The Fourier transformed radar returns are then simultaneously processed by three processing channels, one each for ships, boats and submarines to provide detection of the different size objects. The waveform permits concurrent detection, discrimination, and high resolution range imaging of detected objects within a single dwell, using a single waveform. Thus, a radar search mode using the waveform integrates several search functions without increasing search frame time.

Abstract: A processing method that processes interferometer data to provide for rejection of multipath signal returns from an emitter and computes an improved estimate of the relative angle between the emitter and an interferometer. The present processing method comprises the following steps. Interferometric data is gathered that comprises complex signal amplitudes derived from the emitter at a plurality of emitter angles relative to the interferometer. The complex signal amplitudes derived at each of the plurality of emitter angles are processed by maximizing a predetermined log likelihood function corresponding to a natural logarithm of a predetermined probability density function at each of the plurality of emitter angles to produce a plurality of maximized log likelihood functions. The improved estimate of relative angle between the emitter and the interferometer is made by selecting the emitter angle corresponding to an optimally maximized log likelihood function.

Abstract: Variable array thinning to achieve efficient radar pulse shaping for advanced radar waveforms such as pulse burst or monopulse doppler. At the beginning of the pulse, only a few elements, spread out over the array, are turned on. The effective amplitude can be controlled with precision because each element is either off or at saturation. High efficiency is maintained because the off-state of each element is long enough so that prime power is not consumed.

Abstract: A radar processor is described which performs acceleration compensation for accelerating targets. A set of matched filters is formed that compensates for each one of a predetermined set of target accelerations. The matched filters optimize the signal-to-noise ratio by weighting and combining the Doppler filters over which the target is spreading. As a result, enhanced detection capability of maneuvering targets that spread their energy over Doppler filters is provided. Radar processor loading is reduced, thus making practical the implementation of long coherent arrays.

Abstract: A method is provided for calculating the unambiguous ranges of a radar target in a radar system employing multiple PRFs. The radar system provides digitized data items indicative of return signals in each of a plurality of range intervals for each PRF. A base PRF is selected and a range interval containing a target return signal is selected therefrom. This range interval is correlated with particular range intervals of the remining PRFs to find specific target return signals therefrom which satisfy a first predetermined relationship. This relationship generally provides that a target is identified if a preselected number of correlated range intervals of all PRFs have target return signals therein. If this relationship is satisfied, the target range is calculated from a range equation.

Abstract: A synthetic aperture radar processing system receiving return data from a plurality of transmitted pulses which utilizes frequency alignment for partitioning the received data into patches of data in an orderly sequence, a plurality of patches of data being formed in each of a plurality of range subswaths and being sequentially aligned in range columns. For each subswath, the return data is filtered in patch filters having wide bandwidths and passband overlaps selected so that each patch of data is totally included within a passband. The patch filters are selected for each subswath to provide sequential columns of data. Each patch of data for each subswath is then frequency shifted to an interpolator narrow band filter having a passband selected so that data outside of each patch is eliminated.