Gabor Transform Based Time-frequency Estimation of Ultrasonic Echo Signal

In non-destructive testing, ultrasonic echo is often an overlapping multi-echoes signal with noise. A time- frequency estimation algorithm for ultrasonic echo signal baesd on Gabor transform is presented according to the characteristics of time-frequency analysis in Gabor transform. The similarity (i.e. distance) for echo signal and the Gabor transform window function is modeled. Time Of Flight (TOF) and Center Frequency (CF) of echo signal are estimated by translating model for solving the minimum into solving the maximum of Gabor transform coefficient modulus. Finally, the CRLB is derived to evaluate the performance of the algorithm. The Monte Carlo simulation and experimental results show that the proposed method is efficient and successful. The estimation of single echo or overlapping echoes obtains high accuracy even in low signal to noise ratio. The Mean Square Error (MSE) of estimation achieves CRLB at high SNR, and is close to CRLB, even in low signal to noise ratio.