Maximum fractional cross-correlation spectrum for time of arrival estimation of ultrasonic echoes

Аннотация

In this paper, a maximum fractional cross-correlation spectrum (FCCS) parameter estimation method is proposed to estimate the time of arrival (TOA) and/or time of flight (TOF) of the ultrasonic echoes with a high resolution. The FCCS is the integration of the fractional crosscorrelation of a matched filter and the truncation function of the ultrasonic signal with respect to each time delay, and the range of the integration is limited in the essential-bandwidth which is the bandwidth of the fractional autocorrelation of the ultrasonic echo. If the matched filter matched the truncation function of the ultrasound signal, a local maximum magnitude of the FCCS can be obtained. It can simultaneously produce a measure of TOA of the ultrasonic echoes. The use of FCCS in estimate the TOA or/and TOF of the ultrasonic echoes can eliminate/reduce the noise in an effective manner, even under the very noisy condition, the curve of the FCCS is still smooth with the prominent local extremums. The maximum FCCS parameter estimation method can be repeated with different fractional Fourier transform (FRFT) in order to obtain multiple estimates of TOA of the ultrasonic echoes. These multiple estimates can further be averaged to obtain more robust estimates of the TOA. Numerical simulations and experimental results make evidence the good performance of the proposed approach which has good effect of noise suppression and results in much improved accuracy in the estimation of echo arrival time.