A General FEM Model for Analysis of Third-Order Nonlinearity in RF Surface Acoustic Wave Devices Based on Perturbation Theory.

This article presents a general-purpose model that enables efficient and accurate calculation of third-order nonlinear signals in surface acoustic wave (SAW) devices. This model is based on piezoelectric constitutive equations combined with perturbation theory, which can be analyzed by full finite element method (FEM). For validation, third-order harmonic (H3) responses and intermodulation distortions (IMD3) in SAW resonators are simulated, and their calculation results fit well to experimental data in the literature. Then, the generation mechanisms of the third-order nonlinearity in SAW resonators are discussed. The dominant generation mechanisms for different nonlinear signals and the relation between electrode materials and H3 peak magnitude are revealed, which provides an important guideline for further nonlinear suppression.

Perturbation Analysis of Nonlinearity in Radio-Frequency Bulk Acoustic Wave Resonators Using the Mass-Spring Model.

This article describes derivation of an equivalent circuit for nonlinear responses in film bulk acoustic resonators from the first-order perturbation analysis using the piezoelectric constitutive equations with the h -form. For simplicity, electrodes and piezoelectric layers are considered as mass and spring, respectively, in the derivation. Then, it is demonstrated that the second- and third-order harmonic responses can be simulated well by the circuit. In addition, nonlinearity in the Si substrate is also taken into account and its impact is discussed. It is also discussed how the frequency dependences vary with the nonlinearity mechanisms as a finding from the derived equivalent circuit.

Analysis of SAW Scattering With Discontinuous Periodic Gratings Using Travelling Wave Excitation and Hierarchical Cascading Technique.

This paper proposes a technique to analyze surface acoustic wave (SAW) scattering at discontinuity in grating structures using the hierarchical cascading technique. The traveling wave excitation is applied to generate a specific SAW mode. Then the displacement distribution is obtained for the passive regions. The incident, reflected, and transmitted components are selectively evaluated by the Fourier transform so as to determine the scattering coefficients at the discontinuity. Rayleigh SAWs on the SiO2/128°YX-LiNbO3 structure and SH SAWs on the 42°YX-LiTaO3 structure are used as examples, and the behavior of two kinds of discontinuity are analyzed, and the obtained results are compared with those obtained by the COM model.