Fig. 1. Schematic of frequency shift quadrature fitting demodulation scheme

Fig. 2. Lissajous figure and fitting result formed by interference signals I₁ and I₂

Fig. 3. Unwrap process and filtering for demodulation results. (a) Before unwrap process; (b) after unwrap process; (c) after filtering

Fig. 4. Experimental system for frequency shift quadrature fitting demodulation scheme

Fig. 5. Waveforms of two interference signals I₁ and I₂. (a) Without reference pulse P_rcompensation; (b) with reference pulse P_r compensation

Fig. 6. Demodulation results using frequency-shift quadrature demodulation scheme. (a) Time-domain waveform of demodulation result; (b) local magnification of Fig. 6 (a)

Fig. 7. Demodulation results using frequency-shift fitting quadrature demodulation scheme. (a) Time-domain waveform of demodulation result; (b) local magnification of Fig. 7 (a)

Fig. 8. PSD, SINAD, and THD values of demodulation results of different schemes. (a) Frequency-shift quadrature demodulation scheme; (b) frequency-shift quadrature fitting demodulation scheme

Fig. 9. Time-domain waveforms of two interference signals. (a) Time-domain waveform of I₁; (b) time-domain waveform of I₂

Fig. 10. Time-domain waveforms of cos φ and sin φ. (a) Time-domain waveform of cos φ; (b) time-domain waveform of sin φ

Fig. 11. 1 kHz signal demodulation results. (a) Before unwrap process; (b) after unwrap process; (c) after filtering