Suppression of inharmonic modes using peripheral electrodes in VHF fundamental AT-cut resonators

This paper describes suppression of inharmonic modes in a trapped-energy AT-cut resonator operating at VHF fundamental mode. This resonator has another electrode around a rectangular excitation electrode. The new resonator has the feature to reduce the energy-trapping factor without changing conditions of the excitation electrode. Analyses of one-dimensional energy trapping and finite element analyses are carried out for thickness vibrations in the resonator. The performance of the resonator is verified by experiment. Only the main mode is strongly excited in a 155 MHz resonator. The energy-trapping factor of the resonator is much less than one of the conventional resonator that is the quadruple of Beckmann's number.