Spatial rejection of direct blast interference in multistatic sonars

摘要

A multistatic sonar system (50) employing a short duration automatic gain control (AGC) following beamforming of the return signal to reject spatial transients at the sonar waveform leading and trailing edges. The output of the beamformer (58) is delayed by a delay line (60A) before passing through a programmable gain (60B). The magnitude of an undelayed version of the beamformer output is also squared (60D) and averaged over a time window (60E). This average is used to normalize the delayed value of the beamformer output. The normalized output of the beamformer is compared (60C) with a threshold having a value much greater than unity, and the comparator output controls the gain circuit (60B). When the normalized value of the beamformer output exceeds the threshold value, the gain of the AGC is set to a value much smaller than unity. When the normalized value of the beamformer output does not exceed the threshold, the gain of the AGC is set to unity.