Target reconstruction from broadband acoustic backscatter

Abstract

Broadband acoustic backscatter data are examined for mine reconstruction using LFM and dolphin clicks. Broadband backscatter data from free-field and bottom mines were collected during tests conducted in ARL/UT’s sand tank and sponsored by ONR. The data set includes multi-aspect broadband LFM (50–200 kHz) acoustic backscatter returns from a collection of targets. Both free-field and bottom target data were collected. Bottom target data sets include returns from two different levels of bottom roughness. Each data file is sampled over an interval that is large relative to the echo duration with sufficient sampling both prior to the echo onset and post-echo return to enable meaningful target characterization. Data collected over 360 deg in 2-deg increments are processed to generate a descriptive target pattern. The data are pulse compressed and system artifacts are removed using adjacent channels over the entire frequency band and within subbands. The target pattern is generated by applying the new adaptive wavelet filters to the scattered signals. In particular, the multi-aspect data that have several targets are tested to determine the ability of this new adaptive wavelet transform to reconstruct the external and internal structures of mines. Comparisons are made to previous results generated from broadband dolphin clicks.