A Controllable T-Type Broadband Impedance Matching Network for Ultra-Low Frequency Electroacoustic Transducers

The ultralow frequency (ULF) electroacoustic transducers are normally operated in a high quality factor for efficient radiation and can be treated as nonlinear load. These unique characteristics introduce challenges to the impedance matching of ULF electroacoustic transducer. In other words, advanced impedance matching strategies to simultaneously maintain high transmission efficiency and broadband acoustic radiation are untapped. To address these issues, a controllable T-type broadband impedance matching network (CTIMN) is proposed here. First, the matching principle of CTIMN is newly developed by deriving two equivalent circuits from both the output of power amplifier and the input of ULF electroacoustic transducer. Then, the parameter design method based on the exhaustive method is proposed to yield the optimal parametric design for CTIMN. Combined with the adaptive proportional-resonant control strategy, the operating principle of CTIMN is illustrated. Finally, an electroacoustic transducer is loaded by CTIMN in both simulation and experiments. Compared with existing active matching networks, the proposed CTIMN can double the optimal operating bandwidth and maintain nearly unity power factor in both simulation and experiments, which successfully validates its usefulness and effectiveness.