Ultra-Wideband Mems Filters Using Localized Thinned 128° Y-Cut Thin-Film Lithium Niobate
Jinbo Wu, Shibin Zhang, Pengcheng Zheng, Liping Zhang, Hulin Yao, Xiaoli Fang, Xuedi Tian, Xiaomeng Zhao, Tao Wu, Xin Ou
Abstract
This work demonstrates a first-order antisymmetric Lamb wave (A1) mode MEMS filter with a fractional bandwidth (FBW) exceeding 24%. Based on the localized thinned 128° Y-cut lithium niobate (LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> ) films, the series and shunt A1 mode resonators exhibit excellent effective electromechanical coupling coefficients $\left( {k_{{\text{eff}}}^2} \right)$ of 43.6% and 39.8%, respectively, which is the key to realizing ultra-wideband RF acoustic filters. The fabricated A1 mode filter with a center frequency of 1.79 GHz achieves a minimum insertion loss of 0.61 dB and a maximum 3-dB FBW of 24.6%. After further optimizations, the A1 mode filters will have great potential as broadband acoustic-only filters for 5G New Radio bands.