Electrical Impedance Matching Between Piezoelectric Transducer and Power Amplifier

Electrical impedance matching network (EIMN) is important for the piezoelectric transducer to transmit high-power acoustic signal over a wide bandwidth. Different from the impedance matching between transducers and interface devices with a fixed impedance of 50Ω, this paper presents a novel method of designing an EIMN between transducer and power amplifier (PA) based on matching transformer. First, the equivalent model of the transducer is identified through nonlinear regression process. Then, the matching transformer is designed to meet the specifications of impedance matching and high power operation. To ensure the maximum output power of the PA, a matching transformer is designed to match the impedance of the transducer to a specific resistance which is equal to the ratio of the maximum voltage to the maximum current of the PA. The proposed approach contributes to determining the optimal turns ratio of the matching transformer based on the calculation of the optimal output impedance of the PA. Simulation results demonstrate that the transformer-based EIMN, whose design process is simpler, performs as well as LC-based EIMNs. Experiment based on a B class PA proves the effectiveness and desired performance of the transformer-based EIMN.