Fig. 1. Schematic diagram of the LDV principle

Fig. 2. Noise equivalent model of pre-amplifier circuit

Fig. 3. Baud diagram of pre-amplifier circuit

Fig. 4. Spectral density of input voltage noise of the amplifier

Fig. 5. Spectral density of amplifier output voltage noise

Fig. 6. Output noise distribution curves of pre-amplifier circuit based on OPA657. (a) Gain curves; (b) noise spectral density; (c) total output noise curves

Fig. 7. Output noise density curves for different noise sources of the OPA657

Fig. 8. Distribution of signal, noise, and signal-to-noise ratio

Fig. 9. Output noise density curves of OPA847 for different noise sources

Fig. 10. Total output noise density curves of OPA657 and OPA847. (a) Logarithmic coordinate; (b) linear coordinate

Fig. 11. Comparison of output SNR of OPA657 and OPA847. (a) Logarithmic coordinate; (b) linear coordinate

Fig. 12. Output noise of pre-amplifier circuit

Fig. 13. Relationship between signal-to-noise ratio of Doppler signal and measured velocity. (a) Data 1; (b) data 2; (c) data 3