Research on Linear Frequency Modulation Pulse Compression in Electromagnetic Ultrasonic Thickness Measurement

Abstract

The energy conversion efficiency of the electromagnetic ultrasonic transducer (EMAT) is extremely low. To solve this problem, this paper applied linear frequency modulation (LFM) pulse compression technology to electromagnetic ultrasonic thickness measurement to improve the signal-to-noise ratio. The EMAT excited by chirp signal was simulated by finite element analysis, and the echo signal obtained by the simulation was subjected to pulse compression. After adding noise, the result showed that the EMAT signal-to-noise ratio was increased more than 6dB compared with the echo signal excited by Toneburst signal. In addition, this paper also applied spectrum modification method to suppress the sidelobes of the output signal, further improving the signal-to-noise ratio by 1.6dB.