Finite element modeling and experimental characterization of crosstalk in 1-D CMUT arrays.
Crosstalk is the coupling of energy between the elements of an ultrasonic transducer array. This coupling degrades the performance of transducers in applications such as medical imaging and therapeutics. In this paper, we present an experimental demonstration of guided interface waves in capacitive micromachined ultrasonic transducers (CMUTs). We compare the experimental results to finite element calculations using a commercial package (LS-DYNA) for a 1-D CMUT array operating in the conventional and collapsed modes. An element in the middle of the array was excited with a unipolar voltage pulse, and the displacements were measured using a laser interferometer along the center line of the array elements immersed in soybean oil. We repeated the measurements for an identical CMUT array covered with a 4.5-microm polydimethylsiloxane (PDMS) layer. The main crosstalk mechanism is the dispersive guided modes propagating in the fluid-solid interface. Although the transmitter element had a center frequency of 5.8 MHz with a 130% fractional bandwidth in the conventional operation, the dispersive guided mode was observed with the maximum amplitude at a frequency of 2.1 MHz, and had a cut-off frequency of 4 MHz. In the collapsed operation, the dispersive guided mode was observed with the maximum amplitude at a frequency of 4.0 MHz, and had a cut-off frequency of 10 MHz. Crosstalk level was lower in the collapsed operation (-39 dB) than in the conventional operation (-24.4 dB). The coverage of the PDMS did not significantly affect the crosstalk level, but reduced the phase velocity for both operation modes. Lamb wave modes, A0 and S0, were also observed with crosstalk levels of -40 dB and -65 dB, respectively. We observed excellent agreement between the finite element and the experimental results.
Bayram
Baris
B
Edward L. Ginzton Laboratory, Stanford University, CA 94305, USA. bbayram@gmail.com
Kupnik
Mario
M
Yaralioglu
Goksen G
GG
Oralkan
Omer
O
Ergun
Arif Sanli
AS
Lin
Der-Song
DS
Wong
Serena H
SH
Khuri-Yakub
Butrus T
BT
D016255:Anistreplase; D003198:Computer Simulation; D017076:Computer-Aided Design; D020342:Finite Element Analysis; D007089:Image Enhancement / Q000379:methods*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008962:Models, Theoretical; D014159:Transducers; D014463:Ultrasonography / Q000295:instrumentation* / Q000379:methods
D016255:Anistreplase