Investigation of a Solid-State Tuning Behavior in Lithium Niobate

Electric field-based frequency tuning of acoustic resonators at the material level provides an enabling technology for building complex tunable filters. Tunable acoustic resonators were fabricated in thin plates (h/lambda similar to 0.05) of X-cut lithium niobate (90 degrees, 90 degrees,psi = 170 degrees). Lithium niobate is known for its large electromechanical coupling (SH: K-2 = 40%) and thus applicability for low-insertion loss and wideband filter applications. We demonstrate the effect of a DC bias to shift the resonant frequency by similar to 0.4% by directly tuning the resonator material. The mechanism is based on the nonlinearities that exist in the piezoelectric properties of lithium niobate. Devices centered at 332 MHz achieved frequency tuning of 12 kHz/V through application of a DC bias.