Abstract: A time sequence of raw radar data for a region of space is subdivided into a plurality of processing frames. The processing frames are subdivided into a plurality of processing cells and iteratively processed by selecting a single processing cell for processing, transforming the radar data of the processing cell to form transformed radar data in either the time domain or the Fourier domain. The transformed data is converted to a Power Spectrum Density Matrix in the case of the Fourier domain and a Time Space Correlation Matrix in the case of the time domain. This is smoothed and thresholded and then the clutter for the processing cell is estimated. Estimated local non-speckle clutter is estimated and removed from the transformed radar data, with the cleaned transformed radar data converted back to the time domain if required.

Abstract: An adaptive interference canceller for canceling an interfering signal corresponding to a delayed, frequency translated, amplitude and phase offset version of a transmitted signal contained in a composite received signal relayed through a relay system such as a satellite transponder. The canceller digitally downconverts the received signal and a local replica of the transmitted signal from IF to baseband, applies a variable delay and frequency compensation to the replica as a coarse delay and frequency correction, and tracks fine delay, amplitude and phase differences using an adaptive finite impulse response filter to generate a cancellation signal corresponding to the delayed and frequency shifted version. A minimum output power process produces an error signal that drives the variable delay and adaptive filter to minimize the power in the signal of interest to maximize cancellation of the interfering signal.

Abstract: An adaptive interference canceller for canceling an interfering signal corresponding to a delayed, frequency translated, amplitude and phase offset version of a transmitted signal contained in a composite received signal relayed through a relay system such as a satellite transponder. The canceller digitally downconverts the received signal and a local replica of the transmitted signal from IF to baseband, applies a variable delay and frequency compensation to the replica as a coarse delay and frequency correction, and tracks fine delay, amplitude and phase differences using an adaptive finite impulse response filter to generate a cancellation signal corresponding to the delayed and frequency shifted version. A minimum output power process produces an error signal that drives the variable delay and adaptive filter to minimize the power in the signal of interest to maximize cancellation of the interfering signal.

Abstract: Method and apparatus for non-invasively testing performance of a digital communication system. The test system finds particular application in digital broadcast systems where interruption of regular service for test purposes is impracticable. In one embodiment oriented to digital television cable broadcast systems, unwanted reflections due to loose connectors and other causes may be localized within a subscriber's home. The test system takes advantage of information typically generated by digital receivers to correct for communication channel imperfections. Examples of such information include current filter parameters computed for use in an internal adaptive equalizer, internal loop parameters, and the difference between the signal received and a reconstruction of that signal from the symbols estimated by the receiver.

Abstract: A technique for improving the image quality of facsimile transmissions by actually recovering data corrupted by channel impairments without retransmission. The technique is adaptable to operate with existing facsimile communications standards and does not require modification of transmitter equipment. A significant increase in image quality results. In many cases, otherwise partially illegible documents can be read by applying the image correction technique of the invention.

Abstract: A QAM demodulator that samples an IF input modulated with data at a fractional complex sampling rate between one and two times the data rate. The use of a fractional sampling rate significantly reduces the number of components necessary to implement the demodulator, particularly in the equalizer section of the demodulator which corrects for channel distortion. The fractional sampling rate demodulator architecture of the invention provides a significant reduction in integrated circuit surface area needed in a VLSI implementation.