Monolithic Thin-film Piezoelectric Filters

Abstract

Disclosed are exemplary monolithic acoustically coupled thin film piezoelectric-on-substrate filters that operate in a wide frequency range. The monolithic thin-film-piezoelectric acoustic filters includes a resonant structure that is released from and supported by a substrate that comprises a thin-film piezoelectric layer disposed between a lower electrode and a plurality of electrically isolated upper electrodes. Second order narrowband filters are realized by utilizing coupled resonance modes of a single microstructure. Narrow-bandwidth filters are disclosed that are suitable for channel-select applications in IF and RF bands. Filter Q values of 800 at 250 MHz, 470 at 360 MHz, and 400 at 3.5 GHz for small footprint second-order filters are disclosed. The measured power handling of these devices is high due to the use of high energy density structural material, showing a 0.2 dB compression point of >15 dBm at 360 MHz.