6.5 GHz Longitudinal Leaky SAW Filter Using LiNbO<sub>3</sub>-on-SiC Structure for Wi-Fi 7
Mijing Sun, Shibin Zhang, Pengcheng Zheng, Xiaoli Fang, Xin Ou
Abstract
This work focused on solving the filtering scheme for challenging Wi- Fi 7 bands and successfully implemented the surface acoustic wave (SAW) filters exploiting longitudinal leaky (LL) modes based on thin film X-cut LiNb03-on-SiC (LNOSiC). Here, we initially investigated the relationship between the normalized LiNb03 thickness <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mathbf{h}_{\text{LN}}/\lambda)$</tex> and the resonator response theoretically and experimentally. The lithium niobate film with a thickness of 270 nm was chosen to balance loss and high-frequency side spurious modes. LL-SA W resonators with wavelengths <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\lambda)$</tex> ranging from 0.92 to 1.08 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu\mathrm{m}$</tex> were fabricated, showing scalable resonant frequencies from 5.8 to 6.6 GHz and large K2 of about 19%. An LL-SA W filter with a passband range of 6.297-6.824 GHz, a large 3-dB bandwidth of 527 MHz, and a low insertion loss (IL) of 1.29 dB was successfully realized. The filter meets the requirements of frequency (6 GHz) and channel bandwidth (320 MHz) of Wi-Fi 7, potentially providing a front-end filtering solution for Wi-Fi 7 commercial applications.