Microelectromechanisal system microphones (MEMS microphones) are integrated sound sensors, used in broad spectrum of divices from mobile sound systems to komplex sound matrices, used for sound cameras based on delay beamforming.
In this thesis we developed system for demodulation of one bit pulse density modulated signal (PDM) from MEMS microphone on programmable circuit FPGA. We developed system of sequential filters with decimation of sample frequency based on cascaded integrator comb filter (CIC) and cascade of halfband finite response filters (FIR) and FIR filter with equivalent characteristics.
We made printed circuit board with two MEMS microphone matrices for FPGA development board with one matrix connected to FPGA and second matrix connected to purpuse build integrated circuit ADAU7118 for PDM signal demodulation, whose output signal is connected to FPGA.
We tested demodulation system on FPGA development board MiniZed, where we tranfered demodulated signals on personal computer and used fourier transform analysis of demodulated signal for sinus sound signals frequencies 293 Hz, 1 kHz in 6,4 kHz.
We developed system, which demodulates signals coming from matrix microphones and uses beamforming algorythm. We show result on computer monitor and we got sound location vector from it in form of cartesian vector. We transfered demodulated signal on personal computer through universal asynchronous bus, where we used USB controler on development board for signal transmission.
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