Analysis of total harmonic distortion in phase generated carrier demodulation algorithm by digital arctangent approach

摘要

In this paper, total harmonic distortion (THD) of phase generated carrier demodulation algorithm by digital arctangent approach (PGC-DAT algorithm) is analyzed. THD due to the deviations of modulation depth and carrier phase delay is investigated both theoretically and experimentally. The analytical expression of THD as the function of carrier modulation depth, signal amplitude, initial phase and deviations of modulation depth and carrier phase delay has been derived. According to our analysis, the maximum THD for different initial phases exists, which reaches the peak value when the signal amplitude is close to 1.2 rad. The best modulation depth to minimize the maximum THD is 2 rad. Finally, an experimental system is set up with the mean THD below -60 dB. The analytical expression of THD derived in this paper agrees well with the experimental results.