IJE TRANSACTIONS C: Aspects Vol. 28, No. 6 (June 2015) 888-895    Article in Press

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J. Ahmadnejad, B. Azizollah Ganji and A. Nemati
( Received: May 27, 2014 – Accepted: June 11, 2015 )

Abstract    In this paper, a model for MEMS capacitive microphone is presented for integrated circuits. The microphone has a diaphragm thickness of 1 μm, 0.5 × 0.5 mm2 dimension, and an air gap of 1.0 μm. Using the analytical and simulation results, the important features of MEMS capacitive microphone such as pull-in voltage and sensitivity are obtained 3.8v and 6.916 mV/Pa, respectively while there is no pressure on the diaphragm. The microphone also has a capacitance of 2.3 pF. Using the relation between the capacitance and pressure signal, a 3 ports model for the MEMS microphone is proposed. To bias the microphone, a 2.3 V DC and a 1 GΩ resistor is used. The voltage and current signal of the microphone is proportional to the applied pressure of the acoustic wave. A RC filter is added to circuit to eliminate the low band frequency (≤ 20 Hz) noises. The microphone shows good response to amplitude and frequency changes versus applied pressure signal.


Keywords    MEMS, modeling, capacitive microphone, integrated circuits


چکیده    در این مقاله یک مدل برای میکروفون خازنی MEMS ، جهت استفاده در مدارهای مجتمع نشان داده شده است. میکروفون دارای یک دیافراگم با ضخامت1 μm و ابعاد 0.5 × 0.5 mm و فاصله هوایی 1 μm می باشد. با استفاده از نتایج تحلیلی و شبیه سازی، مشخصات اساسی و مهم میکروفون خازنی MEMS، مانند ولتاژ pull-in و حساسیت، هنگامی که هیچ گونه فشاری به دیافراگم وارد نمی شود، به ترتیب برابر با 3.8 V و 6.916 mV/Pa می باشد. همچنین در این حالت ظرفیت میکروفون برابر 2.3 pF می گردد. با استفاده از روابط میان ظرفیت و سیگنال فشار، یک مدل با سه پورت برای میکروفون MEMS نشان داده می شود. برای بایاس کردن میکروفون از یک منبع ولتاژ 2.3 V و یک مقاومت 1 GΩ استفاده شده است. سیگنال ولتاژ و جریان میکروفون متناسب با فشار اعمال شده به عنوان امواج آکوستیک می باشد. از یک فیلتر RC برای از بین بردن نویزهایی با فرکانس کمتر از 20 Hz استفاده می شود. مدل ارائه شده برای میکروفون پاسخ مناسبی به تغییرات دامنه و فرکانس سیگنال فشار اعمال شده، می دهد.



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