Bayram, Barış
Kupnik, Mario
Khuri-Yakub, Butrus T.
This paper reports on the finite element analysis (FEA) of crosstalk in capacitive micromachined ultrasonic transducer (CMUT) arrays. Finite element calculations using a commercial package (LS-DYNA) were performed for an immersed I-D CMUT array operating in the conventional and collapsed modes. LS-DYNA was used to model the crosstalk in CMUT arrays under specific voltage bias and excitation conditions, and such a modeling is well worth the effort for special-purpose CMUT arrays for ultrasound applications such as medical imaging and high intensity focused ultrasound (HIFU) treatment. Compared to the existing finite element analysis (FEA) in literature, our FEA is distinguished by having all 5 main features together: First, the explicit, time domain solver of LS-DYNA enables the modeling of the actual CMUT array in detail, i.e. all 41 array elements are modeled. Second, user-defined subroutines provide an efficient electrostatic-structural coupling method. Third, the robust contact capability offers the CMUT modeling in collapsed operation. Fourth, a fast method to bias the CMUT array in conventional and collapsed modes is implemented. Fifth, the FEA results are verified with interferometer measurements. Our finite element calculations show that the main crosstalk mechanism is the dispersive guided modes propagating in the fluid-solid interface. Conventional operation has a crosstalk level of -23 dB and the guided modes are not present above the cut-off frequency of 4 MHz. Most importantly, the crosstalk wave has a center frequency of 2.3 MHz with a narrow bandwidth although the transmitter element has a center frequency of 5.8 MHz with more than 130% fractional bandwidth. Crosstalk level is improved to -39 dB in collapsed operation, and the cut-off frequency becomes 10 MHz because of the contact between the membrane and the substrate. The Lamb wave modes have a crosstalk level around -43 dB in both operation modes. These finite element results show excellent agreement with the interferometer measurements of the fabricated CMUT array. Using our verified FEA, we implemented a powerful method for the first time to reduce the crosstalk by impeding the propagation of the guided interface waves. This method is based on the acoustic band gap resulting from the periodic CMUT membranes on the fluid-solid interface. The crosstalk was effectively reduced by 10 dB down to -33 dB in the conventional operation without loss of acoustic pressure of the transmitter element. This method can be easily introduced into the fabrication of I-D and 2-D CMUT arrays to achieve superior crosstalk


Experimental characterization of collapse-mode CMUT operation
Oralkan, Omer; Bayram, Barış; Yaralioglu, Goksen G.; Ergun, A. Sanli; Kupnik, Mario; Yeh, David T.; Wygant, Ira O.; Khuri-Yakub, Butrus T. (2006-08-01)
This paper reports on the experimental characterization of collapse-mode operation of capacitive micromachined ultrasonic transducers (CMUTs). CMUTs are conventionally operated by applying a direct current (DC) bias voltage less than the collapse voltage of the membrane, so that the membrane is deflected toward the bottom electrode. In the conventional regime, there is no contact between the membrane and the substrate; the maximum alternating current (AC) displacement occurs at the center of the membrane. I...
Dynamic analysis of CMUTs in different regimes of operation
Bayram, Barış; Ergun, AS; Yaralioglu, GG; Khuri-Yakub, BT (2003-01-01)
This paper reports on dynamic analysis of an immersed single capacitive micromachined ultrasonic transducer (CMUT) cell transmitting. A water loaded 24 mum circular silicon membrane of a transducer was modeled. The calculated collapse and snapback voltages were 80 V and 50 V, respectively. The resonance frequency, output pressure and nonlinearity of the CMUT in three regimes of operation were determined. These regimes were: a) the conventional regime in which the membrane does not make contact with the subs...
Analytical calculation of collapse voltage of CMUT membrane
Nikoozadeh, A; Bayram, Barış; Yaralioglu, GG; Khuri-Yakub, BT (2004-01-01)
Because the collapse voltage determines the operating point of the capacitive micromachined ultrasonic transducer (CMUT), it is crucial to calculate and control this parameter. One approach uses parallel plate approximation, where a parallel plate motion models the average membrane displacement. This usually yields calculated collapse voltage 25 percent higher than the actual collapse voltage. More accurate calculation involves finite element method (FEM) analysis. However, depending on the required accurac...
Dynamic FEM analysis of multiple cMUT cells in immersion
Bayram, Barış; Ergun, AS; Oralkan, O; Khuri-Yakub, BT (2004-01-01)
This paper reports on the accurate modeling of immersion capacitive micromachined ultrasonic transducers (cMUTs) using the time-domain, nonlinear finite element package, LS-DYNA, developed by Livermore Software Technology Corporation (LSTC). A capacitive micromachined ultrasonic transducer consists of many cMUT cells. In this paper, a square membrane was used as the unit cell to cover the transducer area by periodic replication on the surface. The silicon membrane, silicon oxide post and insulation layer we...
Hacıhabiboğlu, Hüseyin (2016-03-25)
Quaternion Fourier transforms (QFT) provide a powerful tool for the analysis of signals obtained from vector probes. Acoustic particle velocity is one such signal which can be measured with specially designed microphone arrays. This paper presents a time-frequency source separation method based on the short-time quaternion Fourier transform of acoustic particle velocity signals and the k-plane clustering of the vector part of the resulting representation. Two example cases, one with a single and one with tw...
Citation Formats
B. Bayram, M. Kupnik, and B. T. Khuri-Yakub, “ACOUSTIC CROSSTALK REDUCTION METHOD FOR CMUT ARRAYS,” 2006, Accessed: 00, 2020. [Online]. Available: