Near‐field measurement of the scattering characteristics of an object based on Doppler signal filtering.

Abstract

The scattering characteristics of an object can be measured by insonification with tonal signals and reception by a linear array located in the near field of the object. This paper discusses possible signal processing algorithms designed to measure the angular dependence of the target strength of the scatterer. The measurement is based on (1) moving the object parallel to the array, (2) obtaining 2‐D Fourier transform of the received signal in time and space coordinates, (3) the use of a Doppler frequency filter, and (4) selecting the maximum values (as a function of time) of the power spectral density along the trajectory of the moving object in coordinates of frequency and angle. This method gives greater signal to noise ratio than traditional stationary (object not moving) measurement schemes. The possibility of these measurements is estimated using experimental data on the angular and frequency characteristics of reverberation caused by the tonal source. The minimum values of target strength that can be measured in an area with low sea state (i.e., quiet conditions) are determined. [B.M.S. and M.B.S. gratefully acknowledge the generous support of the U.S. Office of Naval Research, ONRG.]