An analog micro-electromechanical XOR

Abstract

This work presents a passive resonant micro-electromechanical phase detector (PD). The PD structure is comprised of two thin film piezoelectric on silicon (TPoS) resonator plates coupled by a silicon beam in the middle. The device exhibits a width extensional resonance mode in which resonant plates vibrate out of phase. When actuated in this mode, the interference of acoustic waves generated from both plates determines the consequent displacement amplitude, and therefore the output signal. Such structure operates as an analog exclusive-OR gate, in which input signals with an identical phase lead to a destructive interference of acoustic waves and therefore a minimum output signal. Out-of-phase input signals (constructive interference), on the other hand, results in the maximum output voltage. Phase sensitivity as high as 1.3 mV/Deg was observed with minimum detectable phase error of 0.006° associated with 8μVrms output voltage standard deviation. Such PD can potentially be used in a MEMS-based analog phase locked loop (PLL). Noise reduction due to the pass-band filtering inherent in the operation of this PD, along with its minimal power consumption are the benefits of the resonant PD over its electronic counterparts.