Abstract: A platform borne sonar system for the detection of targets includes a transmitting projector suspended beneath the water surface from a platform for generating a virtual parametric acoustic array in a water column, forming a beam of acoustic energy. The beam is scannable in azimuth to steer the direct beam in particular directions. A plurality of detectors are arranged to receive the acoustic energy scattered or reflected from any submerged objects present in said direct beam, wherein one or more of the detectors are located the of said direct beam for bistatic reception of the beam reflected off the target. A detector may be suspended beneath the projector for monostatic reception. The direct beam may be scannable in elevation. The direct beam may be narrower vertically than horizontally.

Abstract: A sonar system for use in a water body includes a projector on the bottom of a water body for generating and transmitting a direct beam of acoustic energy. A receiving array is immersed in the water body outside the direct beam for detecting reflections from an target in the direct beam. The receiving array may be a horizontal or vertical linear array of hydrophones in the water body. The array of hydrophones may have output signals coupled to an A/D convertor and a multiplexor for digitizing and multiplexing the signals to prepare for transmission and analysis of the signals. A pair of separated projectors on the bottom of the water body may generate parametric acoustic arrays for transmitting direct beams of acoustic energy through the water body towards each other. A receiving array immersed in the water body outside the direct beams detect any reflections from an object in the acoustic beams.

Abstract: The invention concerns an application of linear system parameter estimation techniques to finite amplitude sonar devices, to extract fine grained angular position information about echo sources. The invention makes use of the fact that the waveform return by a reflecting object within the sonar's beam varies according to its relative angular position from the receiver, and a discovery that this variation may be fit to a linear system model using autoregressive estimation theory to extract the nature of the variation. In all cases, the information is extracted without the mechanical or electrical steering of the sonar transmitting beam.

Abstract: In a digital communications system, one of two tones is selected for each bit, a first tone for a "0" and a second tone for a "1"; the tones are unique for each bit. The tones for all of the bits of a byte are sent simultaneously, in a burst or pulse. At the receiver, a parametric model-based spectrum analysis is performed to find the constituent frequencies which produced the composite spectrum. This spectrum analysis uses autoregressive parameter estimation techniques to determine the most likely combination of frequency components which would have generated the composite spectrum. The combination of frequency components so found is then decoded to yield the corresponding bit values represented by those frequencies. The use of autoregressive spectral analysis techniques to recover the frequency components in the composite signal provides both bandwidth compression (by virtue of increased resolution) and faster signalling rates in transmitting just such signals.