Near 6-GHz Longitudinal Leaky SAW Filters with Spurious Mitigation on LiNbO₃/SiO₂/SiC Platform

This paper reports on the demonstration of high-frequency and spurious-free longitudinal leaky surface acoustic wave (LLSAW) filters utilizing a 32° Y-45° X LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> /SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> /SiC heterostructure. The efficient spurious suppression in a wide frequency range is attained through optimizing critical design parameters such as electrode selection, and the thicknesses of interdigital transducers and LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> plates, specifically employing Cu electrode and thin LiNbO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</inf> film of 180 nm. The fabricated resonators feature phase velocity about 6000 m/s and effective electromechanical coupling factor of 13.4%. Subsequently, 5.66 GHz and 5.96 GHz LLSAW filter with fractional bandwidth of 6.1% and 6.8%, and out-of-band rejection of 26 dB and 28 dB were realized.