Modeling and Parameter Estimation of Ultrasonic Backscattered Echoes

Abstract

Ultrasonic backscattered echoes represent not only the impulse response of the ultrasonic transducer, but also contain information pertaining to the inhomogeneity of the propagation path, effect of frequency dependent absorption and scattering, dispersion effect, and geometric shape, size and orientation of reflectors. Therefore, a well-defined modeling of the backscattered echoes leading to the estimation of arrival time, echo skewness, center frequency, and bandwidth is highly desirable for the nondestructive evaluation of materials [1]. In this paper, we model the backscattered echoes, assuming that all parameters describing the shape of the echo are unknown. Then, iterative parameter estimation techniques such as the Gauss-Newton method [2] or Simplex-Search method [3] have been applied to estimate echo parameters. These algorithms have been evaluated in terms of rate of convergence, sub-optimal estimation due to local minima, and presence of noise.