The Input-output equivalent sources method for fast simulations of distributed nonlinearities in bulk acoustic wave resonators and filters

Abstract

This work presents a new method to analyze weak distributed nonlinear effects, with focus on the generation of harmonics (H) and intermodulation products (IMD) in bulk acoustic wave resonators and filters composed of them. The method consists of finding equivalent current sources (Input-Output Equivalent Sources) at the H or IMD frequencies of interest, that are applied to the boundary nodes of any layer that can contribute to the nonlinearities according to its local nonlinear constitutive equations. The new methodology is compared with the harmonic balance analysis, by means of a commercial tool, of a discretized nonlinear Mason model, which is the most used model for nonlinear bulk acoustic wave resonators. While the computation time is drastically reduced, the results are fully identical. For the simulation of a 7th order filter, the Input-Output Equivalent Sources method is around 700 times faster than the harmonic balance simulations.