Bulk Acoustic Wave Filter Using Piezoelectrically Coupled Resonators

New configurations for bulk acoustic wave (BAW) filters suitable for the ultra high frequency (UHF) band are proposed. In contrast with a monolithic crystal filter, the resonators of the proposed filter are electrically coupled through a piezoelectric film deposited on the filter substrate. Equivalent circuit analysis and simulation results are described. The simulation results suggest the possibility of BAW filters in the UHF band. Because the proposed filter is suitable for the silicon diaphragm structure, development of highly sophisticated integrated electronic circuits with piezoelectric filters is expected.