在采集信号时,如果传感器没有前置放大,

则传感器输出的压电信号的信噪比会比较低。本文利用小波域软阈值滤波方法对未采用前置放大而采样得到的

信号进行小波分析,大幅度地提高了信号的信噪比,提取的目标信号位置与理论位置吻合的很好。这表明可以通

过小波分析方法很好地改善热超声信号的信噪比,从而降低对微波致热超声成像采集系统中前置放大器的要求-When human tissue is irradiated by microwave pulses, there is thermo2acoustic signal due to heat

expansion. Considering the safety, the power of microwave pulse can not be too large. Therefore, the amp litude of the

induced thermo2acoustic signal is very low, and the SNR ( signal to noise ratio) of the p iezoelectric signal from ultrasonic

transducer is very low without p reamp lifier in the transducer. In this paper, a soft2thresholding filteringmethod was used to

p rocess the thermo2acoustic signal which was acquired from an electromagnetic induced thermo2acoustic tomography

( EM ITA) system without p re2amp lifier in the transducer. Itwas shown that the signal’s SNR was greatly imp roved, and

locations of the reconstructed signal pulses agreea verywellwith the theoretical results. This research indicates thatwavelet

analysismethod can greatly imp rove the SNR of the EM ITA signal and may decrease the requirement to p reamp lifier