Quadrature oscillator with pre-distorted waveforms for application in MEMS-based mechanical spectrum analyser

TitleQuadrature oscillator with pre-distorted waveforms for application in MEMS-based mechanical spectrum analyser
Publication TypeConference Paper
Year of Publication2004
Authorsde Graaf, G., L. Mol, L. Rocha, E. Cretu, and R. F. Wolffenbuttel
Conference NameSolid-State Circuits Conference, 2004. ESSCIRC 2004. Proceeding of the 30th European
Pagination407 - 410
Date Publishedsep.
Keywords0 Hz to 1 kHz, AC-operated capacitive accelerometer, accelerometers, capacitive sensors, CMOS, CMOS integrated circuits, cosine-like waveforms, DAC, DDFS, digital-analogue conversion, direct digital synthesis, direct mechanical spectrum analysis, drive voltage frequency sweeping, electrostatic AC field, electrostatic devices, electrostatic force feedback, MEMS-based mechanical spectrum analyser, micromachined capacitive accelerometer, microsensors, predistorted waveforms, quadrature oscillator, scaled resistive string, selectively sensitive accelerometer, sine-like waveforms, spectral analysers, spectral in-zooming, spurious free dynamic range, swept-frequency oscillators, vibration analysis, vibration measurement

An AC-operated capacitive accelerometer with electrostatic force feedback is employed for direct mechanical spectrum analysis. A suitable electrostatic AC field is used to make the accelerometer selectively sensitive to only the coherent mechanical frequency component. By sweeping the frequency of the drive voltage over a selected range, the mechanical (vibration) spectrum is analysed in the mechanical domain. Operation requires the simultaneous generation of predistorted sine- and cosine-like waveforms. A DDFS with DAC, based on a specially scaled resistive string, is designed, fabricated in CMOS and tested. Spurious free dynamic range is 22 dB over a frequency range of DC up to 1 kHz. The spectral performance is comparable to FFT-based systems for spectral analysis on a time series supplied by a conventional accelerometer, while the overall system features a reduced complexity, simple spectral in-zooming and potential for low power consumption.


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