表面波电磁声换能器及电声学特性的研究

电磁超声换能器的非接触、信号重复性好等特点使得其在高温自动检测、材料特性测量等领域有着广泛的应用前景。利用电磁超声技术激发表面波更是行之有效的方法,论文着重于理论分析,对表面波电磁声换能器的物理结构、电声学特性作了较为全面和深入的研究,并用等效电路模型探讨了阻抗匹配的方法。结果表明,电磁声换能器为感性负载,不同于压电器件的容性负载特性,因此对换能器的设计和优化也有着独自的特性;随着提离距离的增大,相应的换能效率也将急剧下降;阻抗匹配对于提高信号的输出强度,抑制谐波分量有着重要的作用,而采用电容并联匹配相比串联匹配,能够提供更高的转换效率。

Electromagnetic transducers for surface wave generation and their electroacoustic characteristics

Electromagnetic transducers have great advantages in automatic inspection and measurement of material characteristics at high temperatures.In particular,surface wave generation by electromagnetic transducer is an effective method.The physical structure and electroacoustic characteristics of surface waves(EMAT) are studies in depth.The impedance matching method is also described through an equivalent circuit model.Conclusions are drawn that EMAT is inductance load rather than capacitive.Therefore the transducer design and optimization is greatly different from piezoelectric transducers.Efficiency is reduced with an increasing lift distance.In addition,impedance matching is important for enhancement of signal amplitude and restraint of harmonic waves.Matching with parallel capacitance can provide better conversion efficiency than with series capacitance.