A tunable low-frequency piezoelectric phase shifter

This paper presents a new technique of shifting the phase of a low-frequency AC voltage. The technique is derived from the multioutput piezoelectric transformer. The piezoelectric phase shifter is made of a piezoelectric ceramic plate operating at the thickness shear vibration mode. The ceramic plate consists of input, output and control parts. The control part is connected to a tunable inductor or capacitor, which can tune the phase shift between the output and input voltages smoothly. The phase shift can be increased by decreasing the inductance or capacitance at the control part. Tuning a DC bias voltage applied to the input part may also change the phase shift. A maximum phase shift of 128° and minimum phase shift of −10° are achieved by the prototype of the phase shifter. The phase shifter has a wide phase shift range, good ability to manage high power and relatively high energy transmission efficiency.