General Electric Company

United States of America As Represented by the Secretary of the Air Force

Robert Leland Nevin

Seth D Silverstein

William E Engeler

Jeffrey Michael Ashe

David Allen Langan

Jean Lienard

Guanghan Xu

Michael Robert Hopple

John Joseph O'Leary

Leonard Joseph Cikotte

A method and apparatus are provided for performing a contrast-based dynamic range management (C-DRM) algorithm. The apparatus comprises an C-DRM processor that performs the C-DRM algorithm of the invention in order to compress an image input to the C-DRM processor down to a desired gray scale range for observation on a display. The C-DRM processor decouples adjustment of image mean values (low frequency) and image contrast values (high frequency), and manages mean and contrast separately. The use of separate mean and contrast modification functions improve on other known compression techniques by providing a more deterministic behavior and reduced complexity, allowing, for example, independent management of negative and positive contrasts. The C-DRM processor can also automatically adapt to the dynamic range of an input image so that the input image thereby applying the minimal compression needed to display the image.

Method and apparatus for performing a contrast based dynamic range management algorithm

An architecture that provides for coherent detection of the relative amplitude and phase of a calibration signal used in the remote calibration of an active transmitting or receiving phased array system employs two coherent signals, one being a reference signal and the other being the calibration signal that contains the relative amplitude and phase information desired in the calibration process. Direct sequence spread spectrum techniques are used to transmit the two coherent signals. Continuous time binary antipodal waveform signals are generated and used to transmit the reference and calibration signals. Relevant amplitude and phase information needed for the calibration can be extracted while compensating for non-synchronized oscillators and the effects of Doppler shifts due to relative motion of the transmitting and receiving platforms. The detection architecture is effective for satellite-based phased array systems, including geostationary, medium and low earth orbit communication satellites, and space-based synthetic aperture radar reconnaissance satellites.

Coherent detection architecture for remote calibration of coherent

An architecture for remote calibration of coherent systems uses coherent reference and calibration signals that contain the relative amplitude and phase information desired in the calibration process. Circuitry extracts the relevant amplitude and phase information needed for the calibration while compensating for non-synchronized clocks and the effects of Doppler shifts due to relative motion of the transmitting and receiver platforms. The coherent detection architectures can be used effectively with any scheme designed to determine the relative amplitudes and phases of the signals emitted from the different elements of the phased array. These architectures are particularly applicable to coherent encoding calibration procedures that enhance the effective SNR by using coherent transmission of orthogonal transform encoded signals from N elements of the phased array. In an example calibration architecture, coherent elemental signals are encoded using controlled switching of the delay phase control circuits themselves to effectively generate a perfect orthogonal transform encoding of the signal vectors, even though the control circuits may be imperfect; no additional encoding hardware is required. The switching is dictated by matrix elements of an N xN invertible binary matrix, with the most preferred embodiment being an orthogonal binary matrix, i.e., a Hadamard matrix. The coherent signals are decoded with the inverse of the same binary matrix used in the control circuit encoding.

A method and apparatus for remotely calibrating a system having a plurality of N elements, such as a phased array system, is provided. The method includes generating coherent signals, such as a calibration signal and a reference signal having a predetermined spectral relationship between one another. The calibration signal which is applied to each respective one of the plurality of N elements can be orthogonally encoded using a unitary transform encoder that uses a predetermined transform matrix, such as a Hadamard transform matrix or a two-dimensional discrete Fourier transform matrix, to generate a set of orthogonally encoded signals. The set of orthogonally encoded signals and the reference signal are transmitted to a remote location. The transmitted set of orthogonally encoded signals is coherently detected at the remote location. The coherently detected set of orthogonally encoded signals is then decoded using the inverse of the predetermined encoding matrix to generate a set of decoded signals. The set of decoded signals is then processed for generating calibration data for each element of the phased array system.

Method and apparatus for remotely calibrating a phased array system used

A method and apparatus for remotely calibrating a system having a plurality of N elements, such as a phased array system, is provided. The method includes generating coherent signals, such as a calibration signal and a reference signal having a predetermined spectral relationship between one another. The calibration signal which is applied to each respective one of the plurality of N elements can be orthogonally encoded based on the entries of a predetermined invertible encoding matrix, such as a binary Hadamard matrix, to generate first and second sets of orthogonally encoded signals. The first and second sets of orthogonally encoded signals and the reference signal are transmitted to a remote location. The transmitted first and second sets of orthogonally encoded signals are coherently detected at the remote location. The coherently detected first and second sets of orthogonally encoded signals are then decoded using the inverse of the predetermined invertible encoding matrix to generate a set of decoded signals. The set of decoded signals is then processed for generating calibration data for each element of the system.

A multi-channel electronic communication system with equalized channels comprises a reference channel and a plurality of object channels. A white noise excitation signal is injected into each channel. Each of the channels is sampled and, for each channel, the resultant samples are windowed and the windowed samples are Fast Fourier Transformed from the time domain to the frequency domain. Power spectral density estimates are determined for each object channel from the windowed samples in that channel. Cross-spectral density estimates for each object channel with respect to the reference channel are determined from the windowed samples in that object channel and the windowed samples in the reference channel. The power spectral density estimates are divided by the cross-spectral density estimates to derive correlation ratios which are converted back to the time domain to specify a corrective equalization filter weight vector for each object channel. An equalization filter in each object channel is then programmed with a respective filter weight vector specified by the corresponding correlation ratio and an equalization filter in the reference channel is programmed with a unity weight vector to equalize the channels in the system.

Apparatus and method for equalizing channels in a multi-channel

A small target phased array Doppler detection system receives signals from remote moving targets and determines Doppler frequency shift and the respective powers of coherent electromagnetic signals for the purpose of detection and identification of relatively small, slow moving targets in the presence of scattering echoes due to clutter. The system employs covariance analysis of the received signals followed by eigenanalysis to produce eigenvectors and eigenvalues. A superresolution algorithm creates dwell manifold vectors which indicate velocities of targets from the eigenvectors. The relative power of radar echoes contribute information relevant to the identification of real moving targets as opposed to false alarms.

Small target doppler detection system

A sensitivity time control circuit for radar receivers, using range gated feedback where the video signal is sampled and compared to a desired signal at intervals based upon range sweep; as the radar antenna is reversing direction, integrated averages of the video signal are used to update the sensitivity time controlled waveform.

Radar sensitivity time control using range gated feedback

A slow scan radar signal is converted from a polar coordinate format to a cartesian coordinate format to permit the radar signal to be displayed on a television type display device. The radar signal, in analog form, is converted to a digital signal, placed in a memory to permit readout of the data in a cartesian coordinate format and converted from a digital to analog signal which may then be applied to the television type display device.

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Schenectady, NY, United States of America

Robert Leland Nevin