A C-band Lithium Niobate MEMS Filter with 10% Fractional Bandwidth for 5G Front-ends

This paper presents a new class of micro-electromechanical system (MEMS) C-band filters for 5G front-ends. The filter is comprised of resonators based on the first-order asymmetric Lamb wave (A1) mode in thin-film lithium niobate. The fabricated filter has been demonstrated at 4.5 GHz with sharp roll-off, flat in-band group delay, and spurious-free response over a wide frequency range. Specifically, the filter shows a 3-dB fractional bandwidth (FBW) of 10%, an insertion loss (IL) of 1.7 dB, an out-of-band (OoB) rejection of -13 dB, and a compact footprint of 0.36 mm
²
. The demonstrations herein mark the largest fractional bandwidth (FBW) achieved for acousticonly filters at 5G frequencies.