Voice coherent laser radar interception method and device for motion Doppler frequency shift compensation

Abstract

The invention discloses a voice coherent laser radar interception method and device for motion Doppler frequency shift compensation. A laser light source in a radar platform outputs a light beam, andthen a polarization beam splitter divides the light beam into a local oscillation light beam and an emission light beam; the emission light beam is emitted to a target; an echo beam of a target is received; the echo light beam and the local oscillation light beam are coherently received and then transmitted to a data processing unit; the data processing unit calculates Doppler frequency shift generated by relative motion of the radar platform and the target, feeds back a control instruction to a frequency shifter according to Doppler frequency shift information, and adjusts the frequency shiftamount of the local oscillation light beam in the frequency shifter to realize Doppler frequency shift real-time compensation in a motion state; and a phase demodulation and unwrapping algorithm is carried out on the compensated collected new data to obtain voice information in real time. According to the invention, voice can be monitored, the monitoring distance is long, the precision is high, the voice is clear, the whole system is miniaturized, the algorithm is simple, and operation is easy.

Description

technical field [0001] The invention relates to the technical field of laser radar, in particular to a voice coherent laser radar interception method and device with motion Doppler frequency shift compensation. Background technique [0002] Voice is an irreplaceable way of information transmission, and voice interception is an important source of intelligence. However, in recent years, terrorist crimes at home and abroad have shown new characteristics of continuous improvement of anti-interception means, continuous enrichment and continuous updating of anti-interception equipment. In order to prevent conversations from being monitored and information leaked, some terrorist organizations, when discussing content such as terrorist premeditation and implementation plans, on the one hand, strictly organize personnel to strengthen peripheral vigilance, so that security personnel cannot approach the interception; on the other hand, they use electromagnetic interference to varying ...

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Problems solved by technology

However, this method can only eliminate the Doppler noise introduced by the movement of the radar platform, and it cannot solve the movement of the target itself, and the system is very complicated and difficult to implement

Lu Tao and others from the Changchun Institute of Optics and Mechanics of the Chinese Academy of Sciences built a part of the optical fiber laser coherent detection system for obtaining long-distance voice signals, and used algorithms to overcome the speckle noise introduced by the relative motion of the radar platform and the target, which can improve the signal of the received voice signal. Noise ratio and intelligibility, but it is difficult to apply to real-time high-precision speech acquisition (the second prior art, see Tao Lv, Xiyu Han et al., "The effect of speckles noise on the Laser Doppler Vibrometry for remote speech detection, ” Optics Communications, Vol. 440, pp. 117-125, 2019.)

Victor C. Chen of the U.S. Naval Research Laboratory summarized the echo spectrum broadening and frequency sideband generation produced by the micro-oscillating motion of the radar target or its components as the micro-Doppler effect, and used joint time-frequency domain analysis to extract the micro-Doppler effect of the target. Doppler features, to obtain the electromagnetic characteristics, geometric structure and motion characteristics of the target, but the overall structure is complex, and the system implementation is difficult (the third prior art, see Victor C. Chen, "The Micro-Doppler Effect in Radar," Artech House, 2011)

[0005] To sum up, the existing voice interception lidar cannot effectively and accurately obtain the Doppler frequency shift generated by the relative motion between the radar platform and the target, so it cannot fundamentally solve the noise caused by the Doppler frequency shift, thus It caused the problems of low voice detection accuracy, loud noise, and unclear voice, and the overall system of voice interception lidar was complex and difficult to operate, which limited the application prospect

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