Reflection of plate acoustic waves produced by a periodic array of mechanical load strips or grooves

The reflection of fundamental acoustic waves propagating in a thin piezoelectric plate by a periodic array of conducting strips of finite thickness or grooves has been theoretically and experimentally investigated. The analysis has shown that electrical shorting and mass loading affect the relationship of neighboring region impedances in a contrary manner. In some cases, these effects are comparable, and there exists a certain strip thickness for each piezoactive fundamental plate mode at which the reflection coefficient can become zero. A high efficiency of grooved reflector for plate acoustic waves was theoretically revealed. Experimental results for mass loading and grooved reflections, which have been obtained for an SH0 wave propagating in the Y-X lithium niobate plate, are in a good agreement with the theory. They show a high efficiency of such reflectors and confirm an opportunity of using a model based on equivalent circuit for the analysis of their operation. Investigations indicate that nearly 100% reflection of the SH0 wave in the lithium niobate plate can be obtained with the use of a mass loading reflector containing 10 silver strips of thickness d/h = 0.08 or a grooved reflector containing eight grooves of depth d/h = 0.25. Here h is the plate thickness and d is the reflector thickness or depth.