Eliminating saturation-type distortions in ultrasonic signals by the least-squares and Papoulis–Gerchberg algorithms

Abstract

Situations may occur in ultrasonic testing in which the values of recorded echo-signals exceed the dynamic range of the receiving amplifier and defectoscope’s analog-to-digital converter. As a result, high-amplitude signals are subjected to a cutoff (clipping) operation and drop in amplitude, thus introducing error in the estimation of reflector dimensions. A declipping method that is based on the Papoulis–Gerchberg algorithm has been suggested and compared against a declipping technique that uses least squares. In numerical and model experiments, the Papoulis–Gerchberg algorithm has demonstrated more stable operation than the least squares for noisy signals and in the case of coarse signal sampling interval.