各向同性晶体栅阵反射系数的二维理论分析

声表面波器件是一个有限弹性体而不是半无限体,依据有限弹性体中的声表面波传输理论,分析声表面波器件周期栅阵对声表面的反射.假定晶体是各向同性的,结合声表面波在周期栅中传播特性的变分原理,用有限弹性体中二维理论的振动位移推导力学负载效应引起的反射系数,求解短路栅阵质量负载的反射系数.通过数值计算得到了玻璃基片不同长度下铝指条的反射系数.发现当基片长度与声波波长之比是奇数倍时,反射系数为正,但绝对值较小;当基片长度与声波波长之比是偶数倍时,反射系数为负,但绝对值较大.这说明要得到较大的反射系数,基片长度应当是声波波长的偶数倍.

Two-dimensional analysis of properties of surface acoustic waves propagating in a finite isotropic solid with periodic metal grating

A surface acoustic waves(SAW) device is usually treated as a semi-infinite elastic body,though it is virtually a finite elastic solid.Based on the two-dimensional theory of finite elastic solids,a new method is developed for the analysis of surface acoustic waves propagating under periodic metal grating on a finite isotropic solid,resembling the Chen and Haus’s theory.The two-dimensional solutions of the mechanical displacements was used to derive the expression of the reflection coefficient dominated by the mechanical loading effect and achieved the value for Al strip on glass substrate.It is shown that when the length of the elastic solid is odd times as long as the wavelength reflection coefficient is positive and its absolute value is smaller,whereas when the length of the elastic solid is even times as long as the wavelength reflection coefficient is negative and its absolute value is bigger.This means that the length of the elastic solid should equal even times as long as the wavelength for achieving bigger reflection coefficient.