Study on resonant frequency and impedance properties of film bulk acoustic resonator

Based on the fundamental piezoelastic theory, the vibration equation of layered FBAR under sine excitation voltage was derived. The unknown constants were calculated with boundary and continuity conditions. The expressions of electrical impedance were obtained from the electrical potential and current. The series and parallel resonance frequency are then calculated when the electrical impedance tends to infinite and zero. The bandwidth and effective electromechanical coupling factor are calculated from the series and parallel resonance frequency. The Bragg reflection layers will reduce the loss of mechanical energy.