Monolithic Multi-Frequency Wideband RF Filters Using Two-Port Laterally Vibrating Lithium Niobate MEMS Resonators

This paper reports on monolithically integrated multifrequency wideband radio frequency (RF) filters based on two-port laterally vibrating lithium niobate microelectromechanical (MEMS) resonators (LVRs). Two-port MEMS resonators based on transferred lithium niobate thin film are designed and experimentally demonstrated. Self-coupled RF filters are implemented by cascading two identical two-port resonators. Modified Mason´s models are used to predict the resonators and filters performance. A good agreement is attained between theory and experimental results. The fabricated two-port devices with center frequencies at 500 and 750 MHz exhibit electromechanical coupling coefficients (k_t² ) of 8% and 14.6%, respectively. As a result, the self-coupled RF filters formed by these resonators are capable of low loss (4 dB) and wideband filtering. Fractional bandwidth of 2% and 3.9% have been achieved-the highest reported for MEMS LVRs. This paper shows that RF-MEMS filters based on LVRs can achieve sufficient bandwidth to cover most of the existing commercial standards.