Abstract: A real time digital filter with its transfer function being matched to a particular signal plus noise condition in a manner that causes the transfer function to adapt to changing signal plus noise conditions. A transversal type of digital filter is disclosed. A general purpose computer calculates coefficients of the filter by continuously monitoring the input signal plus noise in order to maintain the filter's transfer function at an optimum level in view of changing noise conditions.

Abstract: A specially generated broad band radiation signal is passed through a radiation path. The output radiation as modified by that path is compared with the transmitted radiation in a manner to characterize in the frequency domain the radiation path transfer function or the modified radiation by a few constants of a Taylor series expansion. One application of this technique is in sonar or radar work for characterizing the shape of an object in a manner independent of its velocity but with a high signal-to-noise ratio and very good resolution. The comparison of the modified radiation with the transmitted radiation in order to determine the Taylor series coefficients is accomplished by a correlation or matched filtering operation. The technique in its broadest sense also has applications for compensating communication circuits and in parameterizing human speech.

Abstract: A technique for monitoring an object space having known cluttering objects for determining when an object of interest enters the object space. An application of the technique is in sonar supervision of a river or other body of water wherein the entrance into the monitored space by the object of interest, such as a shark or swimmer, is readily detected. Such detection is accomplished by illuminating a monitored object space with broad band radiation. Radiation either reflected from or transmitted through the object is then converted to an electrical signal that is passed through a bank of bandpass filters. The filter outputs are weighted to maximize the receiver's response to the object of interest while minimizing the response to clutter and noise. The technique is based upon the observation that different reflectors give rise to different echo spectra when the reflectors are illuminated with a broad band signal.