SV-SAW RF filters based on low-cost 128°Y LiNbO3/SiO2/poly-Si/Si substrate for 6G cmWave wireless communications
Kai Yang, Jie Chen, Juan Wang, Fuhong Lin, Jiming Fang, Meijuan Li, Junyan Zheng, Zijun Ren, Fangsheng Qian, Haiding Sun, Yansong Yang, Chengjie Zuo
Abstract
Recent advancements in mobile communication have escalated the demand for faster data rates, requiring higher carrier frequencies and compact, high-performance, and low-cost radio frequency (RF) filters. Micro-acoustic resonators offer significant advantages in mobile phone filtering due to their low loss and compact size. Addressing the need for low-cost filter solutions for higher frequencies, this study presents a silicon-substrate-based surface acoustic wave (SAW) technology platform to enable high-performance resonators and filters for 6G X-band (7–12 GHz) centimeter-wave (cmWave) wireless communications. Based on a silicon (Si) substrate, we propose a novel design scheme to excite shear vertical surface acoustic waves (SV-SAW) on a 128°Y LiNbO3/SiO2/poly-Si/Si layer stack and realize high-frequency resonators above 6 GHz with high-performance: electromechanical coupling coefficient (k2) of 7.6% ~ 8.9% and high-quality factor (Q) ranging from 193–679. The synthesized filters based on those high-performance resonators show low insertion loss (1.47 to 2.20 dB) and 3-dB bandwidth from 308 to 373 MHz. Especially, the demonstrated filter with a center frequency (fc) at 8.63 GHz exhibits a low insertion loss of only 1.5 dB, which is the best when compared to all other LiNbO3 acoustic filters in this frequency range, 3-dB bandwidth of 373 MHz, and decent out-of-band rejection across the entire 1–15 GHz range. These results mark a significant step forward for the microwave acoustics field and pave the way for enabling solidly-mounted, low-cost, and miniature-size SAW filters for emerging 6G cmWave wireless communications.