Amplitude modulation-frequency modulation multi-mode noise signal extraction by short-time fourier transform

Lamb wave in structural health monitoring performs as multi-mode amplitude modulation-frequency modulation (AM-FM) signals, which is difficult to be extracted accurately. A new method is proposed to estimate the width of each mode on the short-time Fourier plane. Analyzing the energy distribution of the AM-FM signal, the reconstructing width is divided into two parts, i.e. the instantaneous bandwidth region and the window lobes region. The inverse short-time Fourier transform is then employed to extract each mode accurately by reconstructing the coefficients in these two regions. The effectiveness and robustness are testified by a quantitative comparison analysis of the simulated signal.