Effect of Electric Load Impedances on the Performance of Sandwich Piezoelectric

Based on the electromechanical equivalent cir- cuit, the sandwich piezoelectric transducer with adjustable resonance frequency is studied. The underlying theory of frequency adjustment is its piezoelectric effect. In this pa- per, the influence of electric load impedance (including electric resistance, electric inductance, and electric capac- itance) on the resonance frequency, the antiresonance fre- quency, and the effective electromechanical coupling coef- ficient is analyzed theoretically and experimentally. It is demonstrated that the electric load impedance can change the resonance frequency, the antiresonance frequency, and the effective electromechanical coupling coefficient. When the electric load resistance is increased, the resonance fre- quency and the antiresonance frequency are increased; the effective electromechanical coupling coefficient has a maxi- mum value when the electric load resistance changes. When the electric load resistance becomes large, the effect of the electric load resistance on the effective electromechanical coupling coefficient is negligible. When the electric load in- ductance is increased, the resonance frequency and the an- tiresonance frequency are decreased, whereas the effective electromechanical coupling coefficient is increased. When the electric load capacitance is increased, the resonance frequency, the antiresonance frequency, and the effective electromechanical coupling coefficient are all decreased. It should be noted that when the electric load impedance be- comes large, the effect of the electric load impedance on the resonance frequency, the antiresonance frequency, and the effective electromechanical coupling coefficient of a sand- wich piezoelectric transducer becomes negligible.