声表面波指间多次反射效应的复阻抗理论

对于声表面波的指间多次反射效应,从阻抗不连续的假设出发,提出了复阻抗理论,把指条等效为具有复数阻抗和复数传输相位的传输线,从而反映出指间多次反射效应。引入这样两个复变参量之后,指间多次反射效应就可以用很简明的解析式表达出来。这样,不仅对于等间距换能器的频响和均匀栅格的反射系数,而且对于抽指栅格的反射系数和色散换能器的频响,都可以用解析表达式来表述。与通常使用的矩阵连乘的数值计算方法相比,既可以讨论结果与参量之间的关系,又可以节省数值计算的时间。

A COMPLEX IMPEDANCE THEORY FOR SURFACE ACOUSTIC WAVE INTERELECTRODE MULTIREFLECTION EFFECTS

Starting with the postulation of impedance discontinuity, a complex impedance theory for the interelectrode multireflection effects of surface acoustic wave is presented. In this theory an electrode under the multireflection may be equivalent to a transmission line with a complex wave impedance and a complex propagation phase constant. As a result, the interelectrode multireflection effects could be expressed by simple formula. Thus, not only the frequency response of the equidistance transducers and the reflection coefficients of uniform gratings, but also the reflection coefficients of withdrawed gratings and the frequency responses of the dispersive transducers can be described by these analytical expressions inplace of the commonly used numerical computation of matrix series multiplication which can not tell the relations between the results and the parameters, and is time-consuming in computation.