Time-frequency analysis of backscattered data from a coated strip with a gap

The short-time Fourier transform is applied to analyze the backscattered signal from a coated strip with a gap in the coating. The resulting time-frequency display shows good localization of the different scattering mechanisms. In particular, the time-frequency representation is well suited for identifying the dispersive surface wave contributions. The different scattering mechanisms are further extracted by applying two-dimensional gates in the time-frequency plane. This is a natural extension of the usual time-gating concept and allows the original data to be decomposed into a set of fundamental scattering mechanisms in either the time or the frequency domain