Acoustics and Underwater Technologies Research Center (BASTA)

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Browsing Acoustics and Underwater Technologies Research Center (BASTA) by Author "Köymen, I."

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    Mic-in-CMOS: CMUT as a sealed-gap capacitive microphone
    (IEEE, 2020) Köymen, Hayrettin; Ahiska, Y.; Atalar, Abdullah; Köymen, I.; Taşdelen, A .Sinan; Yılmaz, Mehmet
    The design and production of a CMOS compatible, watertight and ingress-proof CMUT (capacitive micromachined ultrasonic transducer) microphone, mic-in-CMOS, with vacuum-gap is described. We present an analytical model-based approach for the design of mic-in-CMOS, where a basis for quantitative comparison of performance trade-offs is provided. The sealed vacuum gap of the mic-in-CMOS is basically a lossless sensor, free of mechanical noise. Its SNR is determined by the noise of the pre-amplification electronics (the noise contributor in a CMUT with vacuum gap is essentially the radiation resistance, which is less than 0 dBA for audio band for a 1 mm2 device). The design of mic-in-CMOS involves many multilateral trade-offs such as gap height vs membrane thickness vs sensitivity vs need for linear operation vs bias voltage and atmospheric depression, to name few. The mic-inCMOS design can be mass produced using CMOS film stacks only, as such the fabrication process can be carried out entirely in a CMOS processes production line complemented with CMOS compatible post-processing approaches. Mic-inCMOS has the advantage of low production cost with minimal packaging requirement and on-die EMI / EMC.
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    Unbiased charged circular CMUT microphone: lumped-element modeling and performance
    (Institute of Electrical and Electronics Engineers, 2018) Köymen, Hayrettin; Atalar, Abdullah; Güler, S.; Köymen, I.; Taşdelen, A. S.; Ünlügedik, A.
    An energy-consistent lumped-element equivalent circuit model for charged circular capacitive micromachined ultrasonic transducer (CMUT) cell is derived and presented. It is analytically shown and experimentally verified that a series dc voltage source at the electrical terminals is sufficient to model the charging in CMUT. A model-based method for determining this potential from impedance measurements at low bias voltages is presented. The model is validated experimentally using an airborne CMUT, which resonates at 103 kHz. Impedance measurements, reception measurements at resonance and off-resonance, and the transient response of the CMUT are compared with the model predictions.