An X-band Lithium Niobate Acoustic RFFE Filter with FBW of 3.45% and IL of 2.7 dB

This paper presents a micro-electro-mechanical system (MEMS) radio frequency front-end (RFFE) filter at 8.4 GHz. The center frequency of 8.4 GHz is achieved by resorting to the third-order antisymmetric Lamb wave mode (A3) in 650 nm thick Z-cut lith-ium niobate thin film. For the first time, a novel bandwidth-widening technique based on the utilizing of the self-inductance of the top interdigital electrodes is proposed to satisfy the de-mands in miniaturization and wide bandwidth. The fabricated filter has demonstrated a 3 dB fractional bandwidth (FBW) of 3.45% (BW=290 MHz), a minimum insertion loss (IL) of 2.7 dB, and a compact footprint of 0.56 mm2. After utilizing bonding wires as matching inductors, the minimum IL can be decreased to be 2 dB in 50 Ω system.