Encapsulated out-of-plane differential square-plate resonator with integrated actuation electrodes

This paper presents a fully encapsulated 12.5 MHz transverse-mode differential square plate resonator that has out-of-plane actuation electrodes integrated into the thin-film microshell encapsulation. The integration of electrodes minimizes the parasitic resistance, which is generally large for out-of-plane device, and the total footprint of the resonator. Feedthrough capacitance is also minimized by utilizing a differential topology. The AC power handling and DC tuning characteristics are also presented. The plate resonator has no noticeable frequency shift even for AC driving voltages ranging from 223 mV to 2.23 V. The center frequency is still tunable by changing the DC bias voltage, which is ideal for applications that require frequency tunability.