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

Publication Type:

Conference Paper


ESSCIRC 2004, Proceeding of the 30th European Solid-State Circuits Conference, Leuven, Belgium, 21-23 September 2004, p.407-410 (2004)


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-alike
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 DC up to 1 kHz. The
spectral performance is comparable to FFTbased 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.