High-Performance Wideband SAW Filters on LNOI Platform

With the advancement of radio frequency (RF) technology, the exponential increase in transmitted data during the 5G era imposes elevated demands on the bandwidth of surface acoustic wave (SAW) filters. Recently, lithium niobate on insulator (LNOI) platform has emerged as a promising solution for producing wideband SAW filters in 5G communication. In this study, we have investigated the propagation characteristics of SAW on LNOI platform and explored the design and fabrication of various high-performance wideband SAW devices on this platform. The implemented resonators on LNOI platform exhibit scalable and high electromechanical coupling coefficients
$(\boldsymbol{K}^{\mathbf{2}})$
ranging from 14.7% to 31.7%. Furthermore, the SAW filters based on LNOI platform experimentally show a large 3-dB fractional bandwidth (FBW) within the ranges of 8.9% and 30.3%, along with low insertion losses below 1.5 dB and spurious-free responses in the passband. Finally, high-frequency SAW resonators and filters with frequencies ranging from 3 to 5 GHz are implemented on LNOI platform and these high-frequency SAW filters exhibit performances compatible with specifications for the n77, n78, and n79 bands. These results underscore that the LNOI platform significantly broadens the application scope for SAW filters and can pave the way for commercializing wideband SAW filters for the next generation of RF filters.