基于Gabor变换的超声回波信号时频估计

摘要

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.%　　在无损检测中,超声回波往往是一个重叠较严重,含有噪声的多回波信号.根据Gabor变换时频分析的特点,该文提出一种基于Gabor变换的超声回波信号时频估计方法.该文建立回波信号与Gabor变换分析窗函数相似度(即距离)模型,通过模型相似度最小化问题转化为求解回波信号Gabor变换系数模的最大值来估计回波信号的传播时间(TOF)和中心频率(CF),最后推导它们的克拉美-罗界(CRLB)以评价算法的性能.Monte Carlo仿真和实验结果表明该文提出的算法,无论对低信噪比的单回波信号或重叠的多回波信号都能达到较高的精度,而且估计的均方误差在高信噪比时,达到CRLB,即使在低信噪比,也接近CRLB.