Quasi-3D Model for Lateral Resonances on Homogeneous BAW Resonators

Area of Science:

• Electrical Engineering
• Acoustic Physics

Background:

• Lateral modes in Bulk Acoustic Wave (BAW) resonators cause in-band spurious resonances, degrading filter performance.
• Accurate modeling of these lateral resonances is crucial for optimizing BAW resonator design and filter response.

Purpose of the Study:

• To develop a fast and accurate computational method for modeling lateral resonances in BAW resonators.
• To enable precise prediction of resonator input impedance by considering electrode field distributions and piezoelectric coupling.

Main Methods:

• Employed the Transmission Line Matrix (TLM) method, utilizing precomputed Lamb wave dispersion curves and equivalent characteristic impedance for the TE1 mode.
• Implemented a network of transmission lines and nodal Y matrices to couple particle displacement profiles to the electric domain via piezoelectric constitutive relations.

Main Results:

• The proposed TLM model accurately predicts the input impedance of BAW resonators.
• The model demonstrated strong agreement with Finite Element Method (FEM) simulations for Film Bulk Acoustic Resonators (FBARs) and Solidly Mounted Resonators (SMRs), as well as experimental measurements of SMRs.
• The TLM method achieved computational speeds approximately 200 times faster than conventional FEM.

Conclusions:

• The developed TLM-based model offers a significantly faster and accurate alternative for analyzing lateral resonances in BAW resonators.
• This method provides valuable insights into resonator characteristics, aiding in the design of improved RF filters with enhanced in-band responses.