Combined linear and homomorphic deconvolutions for processing bandpass measurements [US flaw detection]

The deconvolution presented is a combination of available techniques. It is effective for extracting the impulse response of individual flaws from ultrasonic data generated by flaw clusters. The technique requires output signals from both the flawed and unflawed systems. By combining linear deconvolution and homomorphic deconvolution, using the complex cepstrum, the desired impulse response can be extracted in cases where the signals contain overlapping wavelets. For the important case of bandpass signals, for which the complex cepstrum does not exist, the technique can still be applied by including a bandpass mapping in conjunction with homomorphic processing. Application of this combined approach to ultrasonic signals reflected from epoxy specimens produced the impulse response of a single cavity from measurements which were bandpass and contained overlapping signals from adjacent cavities. The recovered response, which compared well with the theoretical response of a single cavity, was sufficiently resolved to yield the radius of the spherical cavity