An Online Impedance Analysis and Matching System for Ultrasonic Transducers

Electrical impedance matching of ultrasonic transducers is important in optimizing the energy consumption as well as guaranteeing equipment safety for ultrasonic systems in both laboratories and industries. The existing solutions usually rely on expensive instruments to conduct off-line impedance measurements and deploying static impedance matching networks for each specific transducer across a target frequency band. Here, we present an initial prototype of an online impedance analysis and matching system (OIAMS). In this system, an improved voltage-current method and a phase-difference method were integrated for online impedance measurement in real time, and an L-type matching circuit with variable components helped to achieve dynamic impedance matching. A feedback protocol was embedded in a microcontroller to adjust the matching strategies based on dynamic measurements, while the whole system was controlled through a software interface developed on a LabVIEW platform. Online measurement results showed that OIAMS conducted accurate impedance measurements with a relative error within 3.90% for amplitude and 13.11% for phase across the 100% bandwidth of the tested transducers. After matching, the reflected acoustic power of a 1.00-MHz transducer was reduced by over 50%, increasing the generated sound pressure level by over 2.8 dB across its 70% bandwidth.