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 (LiNbO
₃
) 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 3
^rd
order shear horizontal (SH0) mode resonances. The 3
^rd
order SH0 mode was selected to attain a 3x 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 (k
_t
²
), and a large fractional bandwidth, the ratio of the electrode pitch (W
_p
) to the total width of the resonator (W) has been optimized using finite element analyses.