Abstract
KEYWORDS – slotted membrane, directional microphone, MEMS microphone, capacitive MEMS, silicon condenser microphone
ABSTRACT
We present a directional MEMS microphone suitable for the harsh automotive environment. Silicon-based MEMS microphones have been developed recently due to stable performance for vibration and temperature variation. In order to apply MEMS microphones to automotive applications, higher sensitivity and noise suppression are required. Directionality of a microphone is desired to suppress detrimental effects of noise. Since a directional MEMS microphone receives sounds from the specific direction, it can prevent the noise signals from unwanted directions. In this paper, improved sensitivity with suppressed lower frequency characteristic of the capacitive MEMS microphone is achieved by designing a slotted membrane. The directional MEMS microphone has two acoustic ports, and the directionality is realized by the optimized filter for time delay between the sound signals entering the two acoustic ports. From the measurement of the proposed MEMS microphone, the sensitivity of -46 dBV/Pa and the directivity of 16.4 dB are achieved