A 19GHz Lithium Niobate Acoustic Filter with FBW of 2.4%

This paper presents the first demonstration of a wideband hybrid monolithic acoustic filter in the K-band which exceeds the limitation of electromechanical coupling on the fractional bandwidth (FBW) of acoustic filters. The hybrid filter utilizes the co-design of EM and acoustic to attain wide bandwidth while keeping the advantages of small sizes and high Q in the acoustic domain. The fabricated filter built with resonators having an electromechanical coupling of 0.7% based on the seventh-order antisymmetric Lamb wave mode (A7) has a 3 dB FBW of 2.4% at 19 GHz, and a compact footprint of 1.4 mm².