Browsing by Subject "Pulse excitation"

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    CMUT array element in deep-collapse mode
    (IEEE, 2011) Olcum, Semih; Yamaner F.Y.; Bozkurt, A.; Köymen, Hayrettin; Atalar, Abdullah
    Collapse and deep-collapse mode of operations have boosted the pressure outputs of capacitive micromachined ultrasonic transducers (CMUTs) considerably. In this work, we demonstrate a CMUT element operating in the deep-collapse mode with 25 V pulse excitation and without the effects of charge trapping. The fabricated CMUT element consists of 4 by 4 circular cells with 20 μm radius and 1 μm thick plates suspended over a 50 nm cavity. The overall size of the element is 0.190 mm by 0.19 mm. The collapse voltage of the plates is measured to be approximately 3V. By driving the CMUTs with 25V pulses in the deep-collapse mode without any bias, we achieved 1.2 MPa peak-to-peak pressure output on the surface of the CMUT element with a center frequency of 9 MHz and 100% fractional bandwidth. We applied 1000 consecutive electrical pulses with alternating polarity to the element and witnessed no change in the transmitted acoustic pulse. © 2011 IEEE.
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    An equivalent circuit for collapse operation mode of CMUTs
    (IEEE, 2010) Olcum, Selim; Yamaner F.Y.; Bozkurt, A.; Köymen, Hayrettin; Atalar, Abdullah
    Collapse mode of operation of the capacitive mi-cromachined ultrasonic transducers (CMUTs) was shown to be a very effective way for achieving high output pressures. However, no accurate model exists for understanding the mechanics and limits of the collapse mode. In this work, we extend the analyses made for CMUTs working in uncollapsed mode to collapsed mode. We have developed an equivalent nonlinear electrical circuit that can accurately simulate the mechanical behavior of a CMUT under any large signal electrical excitation. The static and dynamic deflections of a membrane predicted by the model are compared with the finite element simulations. The equivalent circuit model can estimate the static deflection within 1% and the transient behavior of a CMUT membrane within 3% accuracy. The circuit model is also compared to experimental results of pulse excitation applied to fabricated collapse mode CMUTs. The model is suitable as a powerful design and optimization tool for the collapsed as well as the uncollapsed case of CMUTs. © 2010 IEEE.