A study on the Q-factor of STW resonators by a COM theory

Surface transverse wave (STW) resonators exhibit substantial advantages over conventional SAW resonators. However, their analysis is more involved due to the complicated nature of the STW. Among a number of parameters the important Q-factor has faced serious difficulties. At present, none of the theoretical models is concerned with quantitative loss consideration and the establishment of reliable design rules is difficult. We present a theoretical study that permits us to conduct STW loss analysis and predict the resonator Q from the material and layout data. The coupling-of-modes (COM) transmission coefficient is derived by Floquet analysis. Its imaginary part is a measure of STW propagation loss that adds to grating reflection loss. As the overall loss is extremely sensitive to parameter choice, the full numerical search for the optimum design presently discussed can save considerable experimental effort