Abstracts Category : Other

Thermal nonlinearity in radio frequency piezoelectric laterally vibrating resonators

by Ruochen Lu

In recent years, the demand for more wireless bandwidth (BW) has been soaring due to the booming of wireless applications in the marketplace and customers pursuit of higher data rates for communication. This need for more BW will continue to grow as the Internet of Things (IoT) foreshadows more applications requiring wireless connectivity and the use of radio spectrum. As a result, radio frequency (RF) front-end platforms capable of meeting the stringent requirements of higher performance and wider bandwidth are highly sought after and currently being heavily researched. These new platforms should be capable of dynamically operating in several dozens of frequency bands while maintaining high performance. RF piezoelectric laterally vibrating resonators (LVRs) have recently emerged as a promising candidate for front-end filtering and multiplexing in future radios. Compared with the incumbent filtering technology, such as thin-film bulk acoustic resonators (FBARs) and surface acoustic wave resonators (SAWs), this new class of microelectromechanical systems (MEMS) features an assortment of advantages, including integration capability with CMOS, frequency scalability towards higher frequencies, greater electromechanical coupling, and lower loss. Despite these promising features, LVRs still face the challenge of attaining linear response at high power levels and diminishing the intermodulation distortion. The moderate linearity and power handling, which are caused by the intrinsic thermal nonlinearity, produce an unacceptable amount of interference in front-ends. In this thesis, an analytical method has been developed to predict the thermal nonlinearity accurately. It is subsequently leveraged to reduce the nonlinear behavior of LVRs. The organization of the thesis is as follows. In Chapter 1, fundamentals of MEMS resonators are discussed. Chapter 2 explains the operating principles of piezoelectric LVRs in detail, describes the dominant nonlinearities in piezoelectric LVRs, and presents the prior studies on nonlinearities in piezoelectric LVRs. In Chapter 3, a quantitative approach is presented to precisely model the nonlinear dynamics and accurately predict the intermodulation distortions in LVRs. Chapter 4 focuses on the experimental validation of the theoretical analysis. The last chapter concludes with the impact of the method described herein on guiding future optimizations and enhancing the power handling of LVRs for real-world applications.Advisors/Committee Members: Gong, Songbin (advisor).