Electrical performance analysis and characterization of two port piezoelectric resonators

The electrical behavior of two port piezoelectric resonators employing sputtered aluminum nitride as active layer is investigated in this paper. The resonator was tested in a vacuum chamber under controlled pressure from 0.1 mbar to normal atmosphere. The resonator output was found to be a superposition of the mechanical resonance behavior and electrical crosstalk, the latter coming mainly from the coupling feed-through capacitance. A general equivalent circuit model is derived to analyze the resonator's electrical performance. In a polar diagram, the crosstalk introduces an offset of the resonance circle toward the first quadrant, which makes the characterization of the resonator more difficult. Three different methods to calculate the quality factor and resonance frequency of the resonator are discussed.