Lateral- and thickness-field coupling in lithium tetraborate

Calculations have previously been made for rotated y-cuts, including the regions where the quasi-extensional and quasi-shear thickness modes have zero temperature coefficients of frequency. This work extends the calculations to doubly rotated bulk-wave resonators, and computes the coupling factors for the three simple-thickness modes driven by thickness (TE) and lateral (LE) quasistatic electric fields as a function of the orientation angles φ and θ, and the direction of the applied lateral field ψ. Because of the temperature coefficients of the piezoelectric coupling factors, the temperature coefficient of a resonator depend not only upon orientation, but also upon harmonic number and location of the resonator operating point on the immittance circle. These considerations are addressed