Mutual radiation impedance of circular CMUTs on a cylinder

In ultrasound imaging, cross coupling of transducer elements through the medium has significant effect on the frequency response, thus affecting the quality of the ultrasound image. In Side-Looking Intravascular Ultrasound (SL-IVUS) imaging a radial image of the vessel wall is formed using a transducer array in a cylindrical configuration. Recent advances in Capacitive Micromachined Ultrasound Transducer (CMUT) fabrication and integration techniques led to realization of CMUT arrays that can be wrapped into a cylinder shape and mounted on a catheter tip. In this paper, we present the calculation of radiation impedance of un-collapse CMUT arrays on a planar rigid baffle and on a cylinder using Finite Element Method (FEM) simulation. We link the crosstalk between planar CMUT elements with dips in frequency spectrum from experimental data and conclude that decreasing the cylinder radius causes downshift of the dips in frequency response. In the case of our device, these changes are too small to have detrimental effects on the array bandwidth.