A Method for Accurate Modeling of BAW Filters at High Power Levels.

A novel approach for multiphysics modeling of bulk acoustic wave (BAW) filters is presented allowing accurate and at the same time efficient modeling of BAW filters at high power levels. The approach takes the different types of losses and their spatial distribution into account in order to provide the required input for thermal simulation. The temperature distribution determined by thermal simulation is used to modify the geometry and the layer stack of each single resonator of the filter. In this way, the required input for modeling of electromagnetic (EM) and acoustic behavior at high power level is generated. The high accuracy of the modeling approach is verified by the measurements of the S-parameters and the temperature distribution by infrared thermography during high-power loads. Moreover, the influence of the nonlinear behavior on the frequency shift of the resonance frequency is investigated. For this purpose, a parameterized nonlinear Mason model has been combined with a 3-D EM finite-element method and the required nonlinear material parameters were determined by fitting simulation results to the measured polyharmonic distortion model (X-parameters) of a BAW resonator.

Effect of spatial distribution of dissipated power on modeling of SMR BAW resonators at high power levels.

The modeling of bulk acoustic wave resonators at elevated power levels has been improved by taking the spatial distribution of the dominating loss mechanisms into account. The spatial distribution of the dissipated power enables more accurate modeling of the temperature increase caused by the applied power. Thus, it is also possible to more accurately model the frequency shifts of the resonators' impedance curves resulting from the temperature increase caused by the applied power. Simulation and measurement results for the temperatures and impedances of the resonators with different layerstacks at high power loads are presented. The simulation and measurement results are in good agreement, confirming the presented modeling approach. Furthermore, the de-embedding procedure used to obtain vectorial scattering parameters of the resonators during high power loads, the according measurement setup, and the procedure for measuring absolute temperatures by infrared thermography are discussed.