An electrical impedance matching method of dual-frequency transducers for ultrasound internal imaging

A micro single transducer with two resonant frequencies can solve the inherent contradiction between detection depth and resolution by simultaneously emitting two frequency bands of ultrasonic waves. But the difference of impedance values in the two resonant frequency bands seriously affects dual-frequency echo signal efficiency. In order to improve the quality of transducer sensitivity, a dual-frequency electrical impedance matching method is proposed in the study. By selecting a specific matching structure to match one frequency without messing up the impedance of another frequency, the two frequencies can be designed independently to achieve preliminary impedance matching. The matching networks for single frequency are combined to form a complete dualfrequency matching circuit, and adjust the initial matching value to obtain a suitable matching state. The performances of the matching network have been tested and verified by experiments. After matching, the lowfrequency and high-frequency sensitivities of the transducer increased 1.86 times and 2.26 times, respectively. In addition, system noise was also reduced by 29.6% after adding the matching network. The results demonstrate that this dual-frequency matching network can simultaneously increase the amplitude of high-frequency and low-frequency echoes to obtain better quality images.