Spurious-Free Lithium Niobate Bulk Acoustic Resonator for Piezoelectric Power Conversion

SummaryRecently, piezoelectric power conversion has shown great benefits from replacing the bulky and lossy magnetic inductor in a traditional power converter with a piezoelectric resonator due to its compact size and low loss. However, the converter performance is ultimately limited by existing resonator designs, specifically by moderate quality factor (Q), moderate electromechanical coupling $\left( {k_t^2} \right)$, and spurious modes near resonance. This work reports a spurious-free lithium niobate (LiNbO
3
) thickness-extensional mode bulk acoustic resonator design, demonstrating Q of 4000 and $\left( {k_t^2} \right)$ of 30% with a fractional suppressed region of 62%. We first propose a novel grounded ring structure for spurious-free resonator design, then validate its performance experimentally. Upon further work, this design could be extended to applications requiring spurious suppression, such as filters, tunable oscillators, transformers, etc.