FPGA-based real-time acoustic camera using pdm mems microphones with a custom demodulation filter

Acoustic cameras are devices capable of displaying visual representation of sound waves, by means of a microphone array and various signal processing techniques. These devices typically rely on complex hardware configurations, since large number of acquisition channels and processing power are required. However the use of an all-digital signal path makes possible to simplify the hardware by eliminating the need for an analog front-end, yet the usage of 1 bit oversampled ADCs requires a proper demodulation, and may become too demanding for systems with a large number of input channels. In this paper we describe a custom designed high efficiency demodulation filter for a FPGA-based acoustic camera architecture with real-time processing capabilities using PDM MEMS microphones.