电磁超声信号阻塞区等效模型分析

Dead time analysis of electromagnetic acoustic transducer(EMAT)signal using equivalent model

针对电磁超声传感器(electromagnetic acoustic transducer,EMAT)信号阻塞现象,在分析阻塞区形成原因的基础上,建立传感器接收端等效模型,基于该模型得到阻塞区时间、频率的变化规律并进行验证.首先,结合EMAT的工作机制,提出信号阻塞区由接收线圈受到磁场冲激和电压衰减过程组成;然后,根据传感器接收端结构中的磁耦合机制建立等效模型,得到电压衰减过程表达函数;最后,通过实验测得不同接收端结构对应的回路参数和EMAT信号阻塞区的时间、频率,对模型进行验证.研究结果揭示了EMAT结构对信号阻塞区的影响规律,可为EMAT的设计提供参考.

Aiming at dead time of electromagnetic acoustic transducer(EMAT),with the analyses of causes of dead time,equivalent model of transducers'receiving terminal were established,and change regulars of dead time's length and frequency were obtained based on the model.Firstly,combined with the working mechanism of EMATs,it was proposed that dead time is composed of magnetic field impulse process and voltage attenuation process in receiving coil.Secondly,the equivalent model was established according to the magnetic coupling mechanism in transducers'receiving structure,and the expression function of the voltage attenuation process was obtained.Finally,the loop parameters corresponding to different receiving structures and dead time's length and frequency were measured and proved through experiments.This research reveals the influence of EMATs structure on signals'dead time,which can provide relevant guidance for design of EMATs.