Comprehensive review of nonlinear characteristics in surface and bulk acoustic wave devices: Mechanisms, impacts, mitigation strategies, and future prospects

Abstract

With the emergence and development of 5G, radio frequency (RF) communication systems are increasingly imposing stringent requirements on frequency and power. RF front-end filters are critical components, playing a pivotal role in the stable and efficient operation of RF systems. Currently, acoustic filters, including Surface Acoustic Wave (SAW) filters and Bulk Acoustic Wave (BAW) filters, represent the predominant type of RF front-end filters, with resonators based on piezoelectric materials serving as their fundamental building blocks. However, SAW and BAW resonators exhibit significant nonlinear behaviors in high-power RF applications, primarily manifested as frequency shifts, harmonic distortion, and intermodulation distortion. These nonlinear effects are typically attributed to changes in electromechanical coupling mechanism, device temperature, and the elastic modulus of the materials themselves. Under high-power conditions, frequency offset effects can significantly reduce the bandwidth and in-band insertion loss of SAW/BAW filters. The presence of higher harmonics and intermodulation signals is particularly critical in multi-carrier communication systems, potentially severely impacting the signal-to-interference ratio and thus degrading communication quality. Therefore, in-depth investigations into the nonlinear mechanisms of SAW and BAW devices and their effects on device performance are essential for optimizing the design of acoustic filters and enhancing their applicability. This review summarizes the relevant research on the nonlinear characteristics of SAW/BAW devices, covering the mechanisms of nonlinearity, characterization methods, testing systems, simulation models, and mitigation strategies. It comprehensively reveals the current state of nonlinearity in SAW/BAW while discussing existing studies and presenting potential difficulties, challenges, and future directions in SAW/BAW nonlinearity research.