X-Band Miniature Filters Using Lithium Niobate Acoustic Resonators and Bandwidth Widening Technique

This work presents a class of micro-electromechanical system (MEMS)-driven radio frequency filters in the X-band. The X-band center frequencies are achieved by resorting to third-order antisymmetric Lamb wave mode (A3) 650-nm-thick Z-cut lithium niobate thin film. A novel bandwidth (BW) widening technique based on using self-inductance top interdigital transducers and bus lines is proposed overcome limitations set electromechanical coupling (k 2 t ) satisfy demands miniaturization wide BW. Four different designs designed fabricated show trade-off among BW, insertions loss (IL), out-of-band rejections, footprint. Due spurious-free highQ performance A3 resonators, have demonstrated small in-band ripples sharp roll-offs. One these has 3-dB BW 190 MHz, an IL 1.5 dB, compact footprint 0.56 mm . Another design demonstrate 170 2.5 outof-band rejection 28 1