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 V/V are showcased for capacitive loads ranging from 400 fF to 1 pF.