Fig. 1. Workflow diagram of laser coherent radar

Fig. 2. Schematic diagram of mirror frequency

Fig. 3. Construction of quadrature frequency down conversion

Fig. 4. (a) Time domain diagram of radar echo signal; (b) PSD diagram of radar echo signal

Fig. 5. (a) Time domain diagram of mixing results of direct mixing method; (b) PSD diagram of mixing results of direct mixing method

Fig. 6. Amplitude-frequency response and phase-frequency response curve of Hilbert filter

Fig. 7. (a) Time domain diagram of mixing results of orthogonal mixing method; (b) PSD diagram of mixing results of orthogonal mixing method

Fig. 8. Diagram of comparison of SNR of simulation results under different mixing methods

Fig. 9. (a) PSD diagram before compensating for I/Q branch imbalance; (b) PSD diagram after compensating for I/Q branch imbalance

Fig. 10. Diagram of fiber producing 90° phase difference between the LO channels

Fig. 11. Diagram of mixed I/Q signal

Fig. 12. Diagram of SNR and SNR gain of demodulated signals of received signals with different SNR