Sonar beam forming utilizing the chirp Z-transform

Claim 1

Sonar beam forming apparatus for receiving acoustic returns from successive range increments of a target area to be examined as a result of acoustic transmissions sonifying said area, and for forming multiple receiver beams for each said range increment, comprising: (A) a transducer array including a plurality of active elements each operable to provide an output signal in response to said acoustic returns, the collective output signal of said array defining a spatial signal comprised of a plurality of spatial frequency components, each spatial frequency component being indicative of a different one of said receiver beams; (B) encoding means for encoding said spatial signal and including means for providing a frequency chirp signal and means for converting said spatial signal to a corresponding temporal signal including a corresponding plurality of frequency components each indicative of a different one of said receiver beams, and mixing it with said frequency chirp signal to derive an encoded temporal signal; (C) said encoding means including means for varying said encoding as a function of said range increments; (D) decoding means responsive to said encoded temporal signal and operable to separate said different frequency components to provide a plurality of beam signals for each said range increment; and (E) means for processing and displaying said beam signals.