Iterative maximum-likelihood/cross correlation algorithms for echo and pulse time of arrival estimation.

Abstract

For this work, two iterative methods were developed which combine a parametric channel model with the maximum likelihood and cross-correlation estimation techniques in order to estimate the pulse shapes and multiple times of arrival associated with an echo generated when a known pulse encounters a target of unknown impulse response. The modeled echo was assumed to have a generalized form, i.e., it was more complex than a linear combination of delayed and scaled versions of the transmitted pulse. In the short-pulse-duration algorithm developed here, it was assumed that individual events present in the echo did not overlap. For the case of the long-pulse-duration method, this assumption was removed. The techniques were tested using experimental data simulating the targets of a rigid acoustic sphere and dielectric slab, and compared with results obtained from using other methods currently available in the literature. Experimental results demonstrated that the algorithms were successful in determining the proper time delays of the echo events for a variety of received signal-to-noise ratios (S.N.R.s), and compared favorably with other techniques.