Browsing by Author "Kemal, Remzi Erkan"

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    Design and fabrication of high-frequency ultra-wideband 1D CMUT arrays for acoustic angiography applications - preliminary results
    (IEEE, 2018-12-20) Adelegan, O. J.; Kemal, Remzi Erkan; Yamaner, F. Y.; Dayton, P. A.; Oralkan, Ö.; Kemal, Remzi Erkan
    For superharmonic imaging applications involving the use of microbubble contrast agents, transducers that can transmit energy at low frequencies (less than 5 MHz) to excite the microbubbles, and at the same time detect scattered echoes at higher harmonics (greater than 20 MHz) are essential. We explored the advantages of a thin silicon plate with an added central mass combined with a reduced bottom electrode area to further improve the bandwidth of 1D capacitive micromachined ultrasonic transducer arrays. FEM simulation results show that the fabricated devices can transmit at low frequency (<;3 MHz) and receive echoes at high frequency (beyond 30 MHz). This translates into a 180% fractional bandwidth at 17 MHz for the fabricated 1D CMUT array.
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    Equivalent circuit for capacitive micromachined ultrasonic transducers to predict anti-resonances
    (Springer Nature, 2020-12) Kemal, Remzi Erkan; Bozkurt, A.; Yaralıoğlu, Göksen Göksenin; Electrical & Electronics Engineering; YARALIOĞLU, Göksen Göksenin; Kemal, Remzi Erkan
    Equivalent circuit models have been long used to evaluate the dynamics of the capacitive micromachined ultrasonic transducer (CMUT). An important parameter in the characterization of a CMUT is the anti-resonance frequency, which limits the immersion bandwidth. However, there is no equivalent circuit model that can accurately determine the anti-resonance frequency of a membrane. In this work, we present an improved lumped element parametric model for immersed CMUT. We demonstrate that the proposed equivalent circuit model accurately predicts anti-resonance and higher order mode frequencies, in addition to that of the fundamental mode. The proposed circuit model is in good agreement with device characteristics calculated using the finite element method and experimentally measured data.