Resonant frequency sensitive MEMS bandpass filter using capacitive sensing scheme

This paper presents the theoretical and experimental behaviour of microelectromechanical bandpass filters. The proposed bandpass filter can detect frequencies of monitoring structures with high sensitivity using the resonant frequency of micro-resonator of sensor. The micro-resonator contains a proof mass and four supported beams fabricated using a bulk silicon micromachining technology on a silicon-on-insulator wafer. When applying an external force to the system, the device generates a capacitance change, which is converted into a voltage by an electrical circuitry. In good agreement with finite element simulations of the device, experimental results validate that the filter has a center frequency of about 3.3 kHz, a 3 dB bandwidth of 0.562 kHz and a quality factor Q of 5.9 in atmospheric pressure. This paper demonstrates a parallel-resonator filter to increase a monitoring bandwidth. A 3 dB bandwidth of the parallel filter is measured to be 1.25 kHz at atmospheric pressure.