Westinghouse Electric Corporation

James H Mims

Donald R Lampe

Marvin H White

Francis W Hopwood

Raymond G Martin

Henry E Lee

Bruce D Mathews

A wideband radar apparatus is provided having improved interference suppression characteristics. The known time versus bandwidth characteristic of the transmitted pulse is utilized to effect intermediate frequency bandwidth reduction in received swath echo signals. During the interpulse period, basebanded swath echo signals are then subjected to a series of adaptive interference suppressing updates. The adaptive weight vector produced during each of these updates is then applied to the same data used to generate the weights. Preferably, adaptive weight generation is performed in a systolic array according to a QR decomposition algorithm.

Wideband radar system utilizing adaptive interference canceler

A method and apparatus for providing a constant scale factor in azimuth and synchronism of data blocks for a second stage fast Fourier transform in a synthetic aperture radar having two stages of FFT by varying the sampling rate at the output of the first stage FFT as an inverse function of range.

High resolution synthetic aperture radar having rectilinear output image

A method of correcting for focus errors or higher order errors, or various combinations thereof, in the final image effected by the processing of a radar. With regard to correcting focus errors, the method coherently combines the signal focus data from selected target time histories derived by a first stage processor of the radar to form a complex signal representative of the average focus error of the radar image. From the phase of the complex signal is derived a set of focus error compensation signals which are used to compensate for focus errors in the target time histories derived by the first stage processor. With regard to the higher order error correction, the method coherently combines the signal data from selected target time histories derived by the first stage processor by shifting the phase and frequency centroids of each complex signal thereof to a common value. Light filtering may be provided to remove wide band noise with a linear phase filter. Accordingly, the coherently combined and filtered error correction signals are point wise inverted and thereafter used to correct the complex signals of the time histories derived by the first stage processor. An additional embodiment is provided to permit both the focus error and higher order error correction methods to be performed at an intermediate stage in the radar processing.

Method of correcting for errors in radar imaging

In a radar operating in a moving target indication (MTI) mode with frequency diversity by transmitting N+1 pulse bursts and receiving echo signalling therefrom, a radar channel is included for doppler processing the received N+1 pulse echo signal bursts. Each pulse of the same burst envelopes a fixed carrier frequency. The radar is operative to change the transmitted carrier frequency from one pulse burst to another. The radar channel comprises an MTI filter operative as two different orthogonal MTI filters, each having a frequency response similar to an N-pulse MTI filter, to process functionally in parallel a received N+1 pulse echo signal burst to generate a filter signal from each functional filter. Also included is apparatus for combining the two filter signals non-coherently to generate a composite signal corresponding to the N+1 pulse echo signal burst for target detection. The radar channel is operative to process N+1 pulse bursts with either fixed or variable interpulse periods. The two functionally operative filters have frequency response characteristics substantially similar to each other for target echo signals, but effect uncorrelated noise output signals corresponding to a common N+1 pulse echo signal burst.

Radar channel including an orthogonal MTI filter pair

A method of time scheduling mode dwell times corresponding to a multiplicity of targets, displaced in angle, range and velocity, in the frame time of an agile beam coherent radar without reducing the performance of the radar is disclosed. Targets corresponding to a plurality of target mode dwell times scheduled to a common time interval are grouped into a set of pulse repetition frequencies (PRF's) which make the targets visible in both range and doppler. The radar is varied to a different of the set for each coherent integration time of the common time interval. The mode dwell times of the targets of a PRF grouping are interleaved in their corresponding coherent integration time by time positioning the different target time event patterns with respect to the fixed interpulse period thereof to avoid eclipsing of the time events. The time positioning of the event patterns includes a combination of trial positioning and translating each of the target event patterns in a prioritized manner with the purpose of avoiding eclipsing of the time events thereof. The translating of a former target pattern to a new trial position may be performed by delaying the pattern start phasing thereof with respect to the fixed interpulse period of the corresponding integration time.

Method of operating an agile beam coherent radar

A method of processing doppler signal data to provide time and frequency (therefore phase) coincidence for complementary code pairs of a coherent, pulse compression radar using a weighting of every other echo pulse of a particular range cell to guarantee pulse compression sidelobe cancellation in accordance with complementary code theory.

Method of reducing side lobes of complementary coded pulses in a

A beam space adaptive array antenna system utilizing a two-stage Butler matrix configuration is disclosed. The individual elements of one subarray are input to the respective ports of a first-stage Butler matrix and the remaining summed subarray elements are input to a second-stage Butler matrix. The zero order output of the first stage Butler matrix is fed to the input of the second stage Butler matrix.

Antenna array with adaptive sidelobe cancellation

A sampling linearizer including a phase shifter for use in improving the accuracy of an FM generated waveform with respect to a desired frequency rate of change is disclosed. The sampling linearizer comprises an oscillator for generating a reference frequency signal; a mixer governed by the generated FM waveform signal and the reference frequency signal to generate a first signal which is sampled at predetermined sampling times; and a linearizing servo controller which is governed by the sampled signal to reduce the inaccuracies in the genereated FM waveform with respect to the desired frequency rate of change. The sampling linearizer further includes a phase shifter disposed between the oscillator and mixer thereof and operative upon the reference frequency signal to generate another signal, the phase shifter being operative to shift the phase of the another signal with respect to the reference frequency signal as governed by a sequence of control signals representative of predetermined phase shift values. Each resulting phase shift causes the first signal to have a common reference value, preferably zero, concurrent with the predetermined sampling times when the frequency rate of change of the generated FM waveform is changing substantially at the desired rate and causes the first signal to have a phase error with respect to the common reference value concurrent with the sampling times when the frequency of the generated FM waveform is not changing substantially at the desired rate. This sampled phase error first signal is representative of the inaccuracies of the generated FM waveform and is used to govern the linearizing servo controller which regulates the FM waveform generator to reduce these frequency inaccuracies and maintain the frequency of the generated FM waveform substantially at the desired rate of change.

Sampling linearizer utilizing a phase shifter

Extended correlated double sampling (ECDS) for charge transfer devices (CTD) corrects for errors arising in components of the CTD system from the input to the output thereof. Sources of error include bias variations and non-uniformity of thresholds and leakage currents. While applicable to any type of CTD system, for a TDI (time delay integration) application, precise error correction is achieved. Alternate signal level samples and reference level samples, the latter preferably AC zero, are propagated down the CTD channel as a related pair. At the CTD output, the signal and reference level samples of each pair are differenced, thereby correcting the resultant output signal for the noted types of errors. ECDS is compatible with CDS as taught in U.S. Pat. No. 3,781,574 and the two may be used jointly. An application of ECDS in the TDI mode for enhancement of signal outputs from a sensor array is disclosed, along with special parallel signal injection structure and operation for the requisite parallel signal injection into the channel, and special techniques of stabilized charged injection (SCI).

Extended correlated double sampling for charge transfer devices

A programmable analog transversal filter is disclosed for processing analog signals and comprising a charge-coupled device (CCD) for receiving a series of discrete analog signals to be delayed by increasing periods and applied to the outputs of the CCD, and a plurality of MNOS memory devices coupled to the taps of the CCD and programmed so that the output of a CCD tap is multiplied by a particular factor. In turn, the outputs of the MNOS memory devices are summed to provide an output signal ##EQU1## where W.sub.k is the weighting factor associated the k.sup.th MNOS memory device. The weighting factors are set into the system by varying the threshold voltage of the corresponding MNOS device. Positive and negative weighting factors are implemented by using first and second MNOS memory elements for each tap of the CCD, whereby depending upon the program incorporated into the system, one of the first and second MNOS memory devices is programmed to give either a positive weighting factor and the other MNOS memory device a negative weighting factor. Further, a reiterative method of setting the weights into the MNOS memory device is used to compare the system output indicative of the weighting factor as set into the MNOS memory devices, with the desired weighting factor as stored in a suitable storage memory such as a ROM, whereby a correction signal is developed to adjust the threshold voltage V.sub.Th of the MNOS memory device in accordance with the stored weighting factor. In one illustrative embodiment, the weighting factors are set in accordance with sinusoidal signals, whereby the system performs a filtering function to provide an output upon receipt of an input signal of desired frequency. In addition, the MNOS devices are reprogrammable, thus permitting a single such system to be used in many different applications. In this regard, this system is particularly adapted for complex signal processing including filtering, generating desired functions, synthetic aperture radar signal processing and target identification processing.

Programmable analog transversal filter

A method and apparatus for providing motion compensation that allows dynamically changing flight paths during high resolution, squinted, synthetic aperture mapping by making use of a second order motion compensation by means of a two-stage correlator configuration utilizing digital signal processing techniques.

Second order motion compensator for high resolution radar

A programmable analog transversal filter is disclosed for processing analog signals and comprising a charge-coupled device (CCD) for receiving a series of discrete analog signals to be delayed by increasing periods and applied to the outputs of the CCD, and a plurality of MNOS memory devices coupled to the taps of the CCD and being programmed so that the output of a CCD tap is multiplied by a particlar factor. In particular, the MNOS memory devices are disposed in a matrix of rows and columns. The outputs of the MNOS memory devices of each row are summed and the row output signal e(t- ##EQU1## WHERE W.sub.k is the weighting factor associated with the K.sup.th MNOS memory device are applied to corresponding inputs of a parallel-to-series converter taking the form of a CCD. The parallel-to-series converter then is enabled to serially read out the row outputs. The weighting factors are set into the system by varying the threshold voltage of the corresponding MNOS device. Positive and negative weighting factors are implemented by using first and second MNOS memory elements for each tap of the CCD, whereby depending upon the program incorporated into the system, one of the first and second MNOS memory devices is programmed to give a positive weighting factor and the other memory device a negative weighting factor. Further, a reiterative method of setting the weights into the MNOS device is used to compare the system output indicative of the weighting factor as set into one of the MNOS memory devices with the desired weighting factor as stored in a suitable storage memory such as a ROM, whereby a correction signal is developed to adjust the threshold voltage V.sub.Th of the one MNOS memory device in accordance with the stored weighting factor. In one illustrative embodiment, the weighting factors are set in accordance with sinusoidal signals, whereby the system performs a filtering function to provide an output upon receipt of an input signal of desired frequency. In addition, the MNOS devices are reprogrammable, thus permitting a single such system to be used in many different applications. In this regard, this system is particularly adapted for complex signal processing including filtering, generating desired functions, synthetic aperture radar signal processing and target identification processing.

Growing community of inventors

Millersville, MD, United States of America

James H Mims