A 1.17 GHz wideband MEMS filter using higher order SH0 lithium niobate resonators

This paper reports on the design, analysis, and demonstration of a lithium niobate (LiNbO3) wideband radio frequency (RF) microelectromechanical systems (MEMS) filter with a low insertion loss of 2.1 dB, a wide bandwidth of 4.9 %, and a spurious-free passband response at 1.17 GHz. Such high performance is achieved by arraying resonators designed with pronounced 3rd order shear horizontal (SH0) mode resonances. The 3rd order SH0 mode was selected to attain a 3× higher resonant frequency, and subsequently enable a filter center frequency beyond 1 GHz without resorting to costly fine-resolution lithography. To suppress the unwanted modes while maintaining a large electromechanical coupling (kt2), and a large fractional bandwidth, the ratio of the electrode pitch (Wp) to the total width of the resonator (W) has been optimized using finite element analyses.