A Tunable Electrical Impedance Matching System for Dual-Frequency Transducers

Dual-frequency ultrasonic transducers are essential for Endobronchial Ultrasound Endoscopes (EBUS) to achieve clear imaging at various depths. However, the substantial variation in impedance characteristics across dual-frequency bands poses significant challenges for impedance matching. This study introduces a tunable electrical impedance matching system, integrating L-type topology and a dual-channel gating device, specifically designed for dual-frequency ultrasonic transducers. The system dynamically adjusts the topology and parameters of the matching network through efficient control of multiple relays, identifying the optimal matching methods and frequencies within the dual-frequency bands. Dynamic impedance matching experiments within the dual-frequency bands capture echo signals before and after impedance matching, demonstrating significant improvements in echo signal peak-to-peak values and -6dB bandwidths at the optimal matching methods and frequencies. Specifically, enhancements of 12.6% and 5.2% in the 10MHz band, and 9% and 6.4% in the 30MHz band are observed, respectively. These improvements exceed those of other matching techniques at equivalent frequencies and under identical matching methods. The tunable electrical impedance matching system not only determines the most effective matching strategies within the dual-frequency bands but also enhances echo response and bandwidth coverage, thus improving imaging resolution at different depths. The potential applications of this system in dual-frequency ultrasound imaging technology are highly promising.