Spectral evaluation of ultrasonic flaw echoes using Wigner distribution

The performance of the Wigner distribution (WD) is evaluated using several simulated ultrasonic signals. In particular, the WD is used for detecting flaw echoes and characterizing dispersive signals backscattered from inhomogeneous materials. These signals were also characterized using short-time Fourier transform (STFT), and results indicate that STFT outperforms WD. It is concluded that the overall performance of WD is appealing, especially in the case of dispersive signals (i.e. raised cosine chirp) and modulated Gaussian functions, which all yield accurate estimations of the frequency content. However, the WD of the ultrasonic grain signal fails to reveal satisfactory results due to the cross terms, and the detection of flaws is not a trivial task