Author(s) Branch, D.W.; Jensen, D.S.; Nordquist, C.D.; Siddiqui, A.; Douglas, J.K.; Eichenfield, M.; Friedmann, T.A.
Journal IEEE Trans Ultrason Ferroelectr Freq Control
Date Published 2019 Sep 27

Electric field-based frequency tuning of acoustic resonators at the material level may provide an enabling technology for building complex tunable filters. Tunable acoustic resonators were fabricated in thin plates (h/λ ∼ 0.05) of X-cut lithium niobate (LiNbO3) (90°, 90°, Ψ = 170°). LiNbO3 is known for its large electromechanical coupling (K2) for the shear and symmetric Lamb modes (SH0: K2 = 40%, S0: K2 = 30%) in thin plates and thus applicability for low-insertion loss and wideband filter applications. We demonstrate the effect of a dc bias in X-cut LiNbO3 to shift the resonant frequency by ∼ 0.4% through direct tuning of the resonator material. A nonlinear acoustic computation predicted 0.36% tuning, which was in excellent agreement with the tuning measurement. For X-cut, we predicted electrical tuning of the S0 mode up to 1.6% and for Y-cut the electrical tuning of the SH0 and S0 modes was up to 7.0% with K2 = 27.1%. The mechanism is based on the nonlinearities that exist in the piezoelectric properties of LiNbO3. The X-cut SH0 mode resonators were centered near 335 MHz and achieved frequency tuning of 6 kHz/V through application of a dc bias.

DOI 10.1109/TUFFC.2019.2944174
ISSN 1525-8955
Citation IEEE Trans Ultrason Ferroelectr Freq Control. 2019.

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