Analysis of crosstalk between fluid coupled cmut membranes

Acoustical cross-talk in row–column addressed 2-D transducer arrays for ultrasound imaging

“…Previous studies have shown that such waves are the most significant contribution to acoustical cross-talk in 1-D CMUT arrays [5,6]. Eccardt et al have provided a simple description of the dispersion relation of these waves in CMUT arrays based on the assumption of a semi-infinite homogeneous fluid interfaced by a semi-infinite solid with a given surface stiffness per area and mass per area [7]. In this framework, the pressure wave propagating in the fluid at the interface is described by p ¼ expðÀcz þ jkx À jxtÞ with c > 0 being the decay constant in the z-direction perpendicular to the surface.…”

“…The origin of the cross-talk has been identified as being Lamb waves in the silicon substrate, interface waves, and the longitudinal waves emitted into the medium [5][6][7]. Of these, the by far most dominating contribution are the interface waves [6].…”

Rayleigh–bloch waves in CMUT arrays

“…our simulations show that above 1.6 mHz, although there is a nonuniformity in the cell velocities, no standing-waves exist. This cutoff frequency was not predicted by the dispersion curve of surface waves assuming infinitesimally small cmUTs [7]. The cutoff arises from the bragg condition when the cmUT cell pitch is equal to a half wavelength of the r-b wave.…”

“…8 at different frequencies showing a considerable nonuniformity in cell velocities. 7 Fig. 9 shows the plots of the velocity distribution along selected columns of the same array at the same frequencies, quantitatively depicting the uneven velocity distribution.…”

“…Eccardt et al [7] described a dispersive surface wave on cmUT arrays by considering infinitesimally small cmUT cells. They derived an analytical expression that defines the phase velocity of the surface waves as a function of frequency.…”