Near-Spurious-Free Lithium Niobate Resonator for Piezoelectric Power Conversion with Q of 3500 and kt2 of 45%

Piezoelectric power converters, where acoustic resonators replace the inductors as energy storage elements, promise much higher power density and higher efficiency compared to conventional circuits. Recently, lithium niobate (LiNbO3) piezoelectric resonators have been integrated within power converter circuits, showing good conversion efficiency, thanks to their high quality factor (Q) and electromechanical coupling (k(t)(2)). However, the converter output power range is limited by large spurious modes near resonance. This work reports a near-spurious-free LiNbO3 thickness shear (TS) resonator, demonstrating high Q of 3500 and k(t)(2) of 45% at 5.94 MHz, with 0.37 MHz spurious-suppressed region. We first identify the best LiNbO3 crystal orientation for efficient TS resonators, followed by a novel acoustic design without busbars for spurious suppression. Upon optimization, LiNbO3 TS resonators could potentially enable new design space for low-loss and compact power converters.