Wireless Power Transmission Based on Sandwiched Composite Piezoelectric Transducers in Length Extensional Vibration

A new type of wireless power transmission system is proposed. It is composed of two sandwiched composite piezoelectric transducers in length extensional vibration, which are connected together by an intermediate metal transmission cylinder. When the dielectric and mechanical losses are considered, the resonance/antiresonance frequency equations are obtained. The effect of the mechanical and the dielectric loss, the geometrical dimension and the load electric impedance on the effective electromechanical coupling coefficient, the voltage gain, and the power ratio is analyzed. It is shown that the mechanical and the dielectric losses almost have no effect on the resonance/antiresonance frequency. The geometrical dimension has obvious effect on the resonance/antiresonance frequency, the voltage gain, the effective electromechanical coupling coefficient and the power ratio. Corresponding to definite geometrical dimensions, the effective electromechanical coupling coefficient and the voltage gain have maximum values. There is optimum load electric impedance at which the power ratio reaches the maximum value. Two wireless power transmission systems are designed and manufactured; the resonance/antiresonance frequencies, the voltage gain, and the power ratio are measured. It is shown the measured frequencies are in good agreement with the theoretical results.