DUAL FUNCTION REFLECTOR STRUCTURES FOR INTERDIGITAL SAW TRANSDUCERS

摘要

An SAW reflector (302) structure located between multiple interdigitated generator/receivers located on a piezoelectric substrate (100) forming a ladder type SAW device is described. The reflector structure reduces both reflections due to mechanical-electrical loading from the physical presence of generator/receiver fingers without using a split finger arrangement as well as reflections due to the regenerated reflection from the generator/receiver. The reflector has a first acoustic phase center. The generator/receiver has a second acoustic phase center, a regenerated voltage coefficient of reflection r?e? and a mechanical-electrical loading coefficient of reflection r?m?. The reflector is used for simultaneously reflecting both regenerated and mechanical-electrical loading induced reflections from the generator/receiver. The reflector is sized for a strength of reflection equal to the square root of the sum of the regenerated and mechanical-electrical loading reflections squared. The reflector's phase center is positioned an integral number of acoustic wavelengths from the phase center of the generator/receiver plus (or minus) a distance equivalent to a phase angle given by 90 degrees plus the inverse tangent of the ratio of the mechanical-electrical loading reflection to the regenerated reflection times a wavelength dependent proportionality factor.