Abstract: A method and apparatus for classifying objects based upon information conned in the fourth order cumulant derived from energy from the object. Successive pulse returns in active systems and samples in passive systems are converted into vectors based upon the fourth order cumulant information for each successive return or sample. The vectors for each such pulse are compared to corresponding class information based upon the corresponding fourth order cumulant information. The comparison uses loglikelihood ratios of the different pairs of classes. Decision making is based upon the value of each loglikelihood ratio in comparison with a class threshold.

Abstract: A method of extracting target range and Doppler information from a Dopplepread signal is provided. An acoustic waveform is transmitted underwater and impinges upon a submerged Doppler-spread target. Doppler-spread sonar echoes resulting from the transmitted waveform are received and digitized. The received sonar echo is separated into its inphase and quadrature components thereby forming a complex vector function. A fourth-order cumulant spectrum is generated from the complex vector function based upon three time delays. In order to extract the range and Doppler information from the Doppler-spread signal, the first of the time delays is set equal to zero while the second and third time delays are set equal to one another.

Abstract: Apparatus and method for discriminating against non-Gaussian noise. Analog signals from an array of sensors are converted to real and imaginary digital representations and processed such that non-Gaussian noise is separated from signals of interest. The processor uses estimates of Kurtosis and quantiles from either past or adjacent frequency components to construct non-linear elements, which are then used to process remaining signal data to improve the signal-to-noise ratio thereof by removing non-Gaussian noise therefrom.