EMAT非线性高次谐波提取方法与电路设计

Nonlinear Ultrasonic Harmonic Wave Extraction Method and Circuit Design for Electromagnetic Acoustic Transducer Detection

由于电磁超声换能器(EMAT)非线性高次谐波信号微弱且通常湮没于基频和噪声信号中,EMAT高次谐波信号的提取对于提高EMAT纳米级微结构缺陷非接触原位检测精度、降低检测成本具有重要的作用。文中研究了脉冲激励下EMAT微弱信号宽带前置放大后时域和频域信号特征,分析了EMAT接收信号超外差调频放大方法以及非线性高次谐波信号幅值、相位提取的互相关锁相检波方法的理论基础,并针对实测的EMAT信号进行了高次谐波提取分析。同时,研究了EMAT非线性高次谐波提取电路设计方法。研究结果对深入研究开发EMAT非线性检测器具有重要的理论和实际意义。

The high order harmonic signals of electromagnetic acoustic Transducer（ EMAT） are very weak and usually submerged in the fundamental wave signal and noise signals. It is of value for not only improving the accuracy of in-situ nanometer level micro-structure defects by non-contact EMAT detection method,but also reducing the test cost. The paper studied the timedomain and frequency domain signal features of EMAT receiving coils after wideband preamplified processing at the condition of pulse excitation,and analyzed the theory basis of superheterodyne frequency modulation amplifying method,and cross-correlation phase-locked method to extract the signal amplitude and phase,and simulation experiments were carried out to extract the high-order harmonic wave signal for pulse excitation EMAT signals. At the same time,the paper studied the circuit design method of the high-order harmonic wave extraction. The research results are of important theoretical and practical significance for further studying EMAT non-linear detector.