Mechanic-electric-circuit coupling analysis of BAW filter based on FDTD method

In this paper, mechanic-electric-circuit coupling algorithm based on the finite-difference time-domain (FDTD) method is proposed to analyze a one-order microwave bulk acoustic wave (BAW) filter. FDTD method is used to solve the coupled mechanic-electric-circuit system equations to obtain the voltage and current at port position of the BAW filter in the time domain. Then S parameters of the BAW filter in the frequency domain are calculated using the Fourier transform. In our work, a one-order BAW filter consists of two film bulk acoustic resonators (FBARs) by means of series and parallel. These two FBARs in the BAW filter are coupled together through an equivalent electrical connection. Similarly, multiphysical mechanic-electric-circuit analysis of the BAW filter is implemented in the commercial software COMSOL, which is realized by the time-domain finite element method. The accuracy of the proposed method is verified by comparison with simulation results in COMSOL. In addition, the computational time and memory of the proposed method have obvious advantages over those of COMSOL.