Novel FEM Models of Intermodulation Effects in BAW and SAW Devices

The nonlinear intermodulation effect in piezoelectric devices was studied By using the three-dimensional equations of nonlinear piezoelectricity and the method of harmonic balance, we have formulated and derived coupled sets of nonlinear piezoelectric equations in the frequency domain for intermodulation effects. The coupled sets of equations could be embedded in COMSOL FEM models. In order to check the validity and accuracy of the FEM models we studied the third order intermodulation effects in AT-cut quartz resonators. Our three-dimensional FEM model results compared well with the analytical one-dimensional results by Tiersten and with the experimental results by Smythe. The FEM models could be used for simulating intermodulation effects in BAW and SAW piezoelectric devices provided that the nonlinear material constants are available and are accurate.