Analysis of acoustic impedance matching in dual-band ultrasound transducers.

Dual-frequency band probes are needed for ultrasound ( US) reverberation suppression and are useful for image-guided US therapy. A challenge is to design transducer stacks that achieve high band-width and efficiency at both operating frequencies when the frequencies are widely separated with a frequency ratio similar to 6: 1-20: 1. This paper studies the loading and backing conditions of transducers in such stacks. Three stack configurations are presented and analyzed using one-dimensional models. It is shown that a configuration with three layers of material separating the transducers is favorable, as it reduces high frequency ringing by similar to 20 dB compared to other designs, and matches the low frequency (LF) transducer to the load at a lower frequency. In some cases, the LF load matching is governed by a simple mass-spring interaction in spite of having a complicated matching structure. The proposed design should yield improved performance of reverberation suppression algorithms. Its suitability for reduction of probe heating, also in single-band probes, should be investigated. (C) 2017 Acoustical Society of America.