Direction sensitive detection of sonar signals

Abstract

Sonar signals have an inherent doppler shift which is several orders of magnitude higher than the signal bandwidth and corresponds to the unknown relative velocity of the target. The problem of detecting such signals could be viewed in two ways depending upon the assumption regarding the probability density function of the unknown doppler shift. First, the doppler frequency could be assumed to have a continous uniform distribution within the band of intrest. Proceeding with this assumption, the optimum receivcer will turn out to be the standard square law envelope detector. But if a discreet distribution for the doppler shift is assumed, the structure reduces to the doppler processor of Whalen [1].