Improved phase-generated carrier demodulation technique based on LM algorithm with low harmonic distortion and high stability

In this paper, a multi-harmonic mixing demodulation scheme based on Levenberg-Marquardt (LM) algorithm, called PGC-LM-Arctan, is proposed to eliminate the influence of phase modulation depth on demodulation results. The relation between the C value and ratio of Bessel function is fitted by LM algorithm, and then the ratio of fourth harmonic and second harmonic is substituted into the above relation. The C value is calculated to eliminate the influence of coefficients on the demodulation results in Arctan algorithm. The experimental results show that when the modulation depth is from 1.5 rad to 4.8 rad, the harmonic distortion of the improved algorithm is lower than 0.7 %, which keeps the best level of the traditional PGC algorithm. The signal-to-noise-anddistortion-ratio is 41.69 dB, which is 17.58 dB higher than the traditional PGC-Arctan algorithm.