On the optimum resonance of giant magnetostrictive ultrasonic transducer with capacitance-based impedance compensation

Abstract

Due to the large magnetostrictive coefficient, high power density and fast response speed of giant magnetostrictive materials, the giant magnetostrictive ultrasonic transducer (GMUT) becomes an increasingly popular research topic in making a high-power ultrasonic vibration. However, due to the complex energy conversion mechanism of the GMUT, the optimum resonance of the GMUT cannot be determined to utilize the ultrasonic energy to the maximum extent. To solve this problem, an equivalent circuit model of the GMUT is improved with capacitance-based impedance compensation, and the influence of the compensation capacitance on the GMUT is studied by the parameter characterization of the extreme currents and resistance points (X = 0 Ω) in the impedance circle derived from the improved model. Thus, an impedance-compensation method for determining the maximum amplitude of the GMUT is proposed to reach the optimum resonance. Experimental results show that the improved model corresponds well with the impedance circle under different compensation capacitances, and the maximum amplitude related to the optimum resonance is determined at the optimal point where the mechanical resonance and electrical resonance occur nearly simultaneously.