Extraction of COM parameters from field distribution

On basis of Coupling of Modes (COM) model, the field distribution within short-circuited grating and open-circuited grating is studied. The behavior of forward and backward surface acoustic waves among the gratings can be easily explained by the action of the reflection coefficient and the propagation of the wave in a media without reflection. So according to the parameters of the distribution curves of forward and backward surface acoustic waves, one can extract the COM parameters as some characteristics of the distribution curves. For example, from the period of the amplitude of backward wave distribution along the locations; and from the ratio between backward wave and forward wave, etc., it is easily to obtain the COM parameters. Once the distribution of the backward and forward waves are known (either from the experimental detection or from FEM/BEM calculation), the COM parameters are obtained. Such COM parameters are functions of frequency, which is very important in device simulation.