Obdelava signalov mikroelektromehanskih mikrofonov v programirljivem vezju

POLJANŠEK, MATEJ (author), Trost, Andrej (mentor)

Mikroelektromehanski mikrofoni (MEMS) so integrirani zvočni senzorji, uporabljeni v širokem spektru naprav, od prenosnih zvočnih sistemov do kompleksnih zvočnih matrik, uporabljenih za zvočne kamere na principu oblikovanja zvočnega snopa. V tem delu smo razvili sistem za demodulacijo enobitnega pulzno gostotno moduliranega signala (PDM) iz MEMS mikrofona na programirljivem vezju FPGA. Razvili smo sistem sekvenčnih sit z decimacijo vzorčne frekvence na osnovi kaskadnega integracijskega “comb” sita (CIC), kaskade polpasovnih sit s končnim impulznim odzivom (FIR) in FIR sita z enkvivalentno karakteristiko. Izdelali smo tiskano vezje z dvema matrikama MEMS mikrofonov za FPGA razvojno ploščo, z eno matriko povezano na FPGA in drugo matriko povezano na namensko integrirano vezje ADAU7118 za demodulacijo PDM signala, katerega izhodni signal peljemo na FPGA. Izvedli smo testiranje demodulacijskega sistema na FPGA razvojni plošči MiniZed, kjer smo demodulirane signale prenesli na osebni računalnik in izvedli frekvenčno analizo demoduliranega signala za zvočne sinusne signale frekvenc 293 Hz, 1 kHz in 6,4 kHz. Zasnovali smo sistem, ki demodulira signale matrike mikrofonov in iz le-teh oblikuje zvočni snop, ki ga prikažemo na računalniškem monitorju in iz katerega pridobimo relativno lokacijo izvora zvočnega signala v obliki kartezičnega vektorja. Demodulirani zvočni signal prenašamo na osebni računalnik preko povezave z univerzalnim asinhronim vodilom, kjer smo uporabili USB krmilnik na razvojni plošči za prenos podatkov.

• Language: Slovenian
• Keywords: MEMS mikrofon, pulzno gostotna modulacija, oblikovanje zvočnega snopa, CIC sito, FIR sito, decimacija vzorčne frekvence, FPGA razvojna plošča
• Work type: Master's thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2024
• PID: 20.500.12556/RUL-161288
• Publication date in RUL: 09.09.2024

Secondary language

• Language: English
• Title: Signal processing of microelectromechanical microphones in a programmable circuit

Abstract

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.

• Keywords: MEMS microphone, pulse density modulation, beamforming, CIC filter, FIR filter, sampling frequency decimation, FPGA development board