The 180 Degree Reflectivity and Velocity Perturbation of Thin Metal Dots

Abstract

Reflective arrays of rectangular thin metal 'dots' spaced in a regular or near regular grid pattern, such as have been used in surface acoustic wave resonators and in-line dot RACs on LiNbO//3 , are analyzed. The half-wavelength spacing of dots required leads to capacitative coupling between adjacent dots. The charge distribution induced on the dots by the passage of the SAW is presented including the coupling. The 180 degree SAW reflectivity of the dots and the SAW velocity perturbation through the dot array are given for a range of dot sizes. These are shown to be in good agreement with experimental results. The work establishes that the method of analysis can form the basis of the design of 180 degree reflective weighted dot arrays, allowing them to be implemented through varying dot density and/or by varying dot dimensions.