Modelling of tunable bulk acoustic resonators and filters with induced piezoelectric effect in BSTO film in a wide temperature range

In this paper we discuss a potential realizability of a tunable bulk acoustic filter based on BSTO film for microwave applications. The estimation of characteristics of the tunable TFBAR was done by processing the experimental data obtained for the BSTO resonator using the model of the induced piezoelectric effect. In the model are taken into consideration temperature dependent acoustic characteristics of the BSTO film based TFBAR. Simulated results of temperature dependence of the electromechanical coupling coefficient and frequency shift of the resonance and antiresonance peaks of the TFBAR as compared with measurement are presented in the paper. It is demonstrated electromechanical coupling coefficient and consequently acoustic resonances become stronger with decreasing temperature. The third-order tunable TFBAR filter was designed. The necessary set of the acoustic and electric parameters of the tunable ferroelectric based TFBAR was proclaimed. The 10% tunability of the TFBAR filter pass band was estimated by a simulation. The simulated characteristics were obtained taking into consideration a real structure of the BSTO based resonators (electrodes and acoustic mirror).