Abstract
An H-shaped longitudinal resonator mode of a piezo-ceramic has been used as a filter for the intermediate frequency (IF). However, the design of the filter of an H-shaped resonator is not easy because the measured vales of resonant frequency do not agree with the calculated ones, which were roughly given by using its equivalent network theory. In this paper, the H-shaped resonator is investigated by using the finite element method in order to make the design of the filter easy practically. In the first part of this paper, the relations between the dimensions of each several parts of the H-shaped vibrator and the resonant frequencies are definitely shown by some analyses and experiments. The second part contains the analys of vibrational modes ; that is, it is found that the vibrational nodal points in common with both resonances of in-phase mode and out-ofphase mode exist under the condition of some specific dimensions. Therefore, it is expected that, by supporting the resonator at these nodal points, decrease of its quality factor Q can be prevented. This is confirmed experimentally in this paper Finally, one example of the IF filter using this H-shaped vibrator and its filter characteristic are shown.
