Abstract
A novel ameliorated phase generated carrier (PGC) demodulation
algorithm based on arctangent function and differential-self-multiplying
(DSM) is proposed in this paper. The harmonic distortion due to nonlinearity
and the stability with light intensity disturbance (LID) are investigated
both theoretically and experimentally. The nonlinearity of the PGC
demodulation algorithm has been analyzed and an analytical expression of the
total-harmonic-distortion (THD) has been derived. Experimental results have
confirmed the low harmonic distortion of the ameliorated PGC algorithm as
expected by the theoretical analysis. Compared with the traditional
PGC-arctan and PGC-DCM algorithm, the ameliorated PGC algorithm has a much
lower THD as well as a better signal-to-noise-and-distortion (SINAD). A THD
of below 0.1% and a SINAD of 60 dB have been achieved with PGC modulation
depth (<i>C</i> value) ranges from 1.5 to 3.5 rad. The stability performance with
LID has also been studied. The ameliorated PGC algorithm has a much higher
stability than the PGC-DCM algorithm. It can keep stable operations with LID
depth as large as 26.5 dB and LID frequency as high as 1 kHz. The system
employing the ameliorated PGC demodulation algorithm has a minimum
detectable phase shift of 5 μrad/√Hz @ 1 kHz, a large dynamic range of 120 dB @ 100 Hz, and a high
linearity of better than 99.99%.
© 2010 IEEE
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