A P-Matrix Model for Third Order Electric and Acoustic Nonlinearities in TC-SAW Devices

A nonlinear P-Matrix model is implemented to describe the generation of third harmonic (H3)and third order intermodulation (IMD3)products in temperature compensated surface acoustic wave (TC-SAW)devices on LiNbO ₃ -rot 128°YX substrate. The constitutive equations are extended by considering the source terms of mixed acoustic and electric origin, where the nonlinear sources are written as sum of mixed third order terms in strain and electric field. Two nonlinear sources are introduced, one is the directly induced nonlinear current at the electrode finger and another is due to acoustic sources distributed in the device, which indirectly lead to a nonlinear current at the electrodes. In total eight source terms and therefore, eight nonlinear coefficients are introduced to extend the P-Matrix approach. The third order nonlinear model shows a good fit to different H3 and IMD3 measurements for duplexers operating in frequency range of LTE band. The nonlinear constants extracted provide a broad dataset for predicting the nonlinear performance. Finally, the role of electric and acoustic contributions to the nonlinear responses of TC-SAW devices is discussed.