High-Figure-of-Merit X-Cut Lithium Niobate MEMS Resonators Operating Around 50 MHz for Large Passive Voltage Amplification in Radio Frequency Applications

This article reports on the modeling, design, fabrication, and testing of high-performance X-cut lithium niobate (LN) laterally vibrating resonators (LVRs) operating around 50 MHz. The objective of this work is to exploit the high figure of merit (FoM)-product of quality factor at series resonance (Q(s)) and electromechanical coupling (k(t)(2))-to provide for large passive voltage amplification in the front end of emerging radio frequency (RF) applications, i.e., wake-up radio receivers (WuRx). Finite-element analysis (FEA) is performed to optimize the devices' geometry and ensure simultaneous high Q(s) and k(t)(2). Resonators exhibiting Q(s) > 5300 and k(t)(2) > 27% are demonstrated, with FoM > 1650-the highest value recorded for resonators in the megahertz range to the best of our knowledge. Finally, passive voltage gains between 35 and 57 VN are showcased for capacitive loads ranging from 400 fF to 1 pF.