激光微多普勒探测系统中降低相位噪音影响的方法研究

相干微多普勒激光雷达具有探测灵敏度高、探测信息量大等特点,特别适合于动目标探测、目标特征识别等应用.本文从线宽和探测距离两个方面讨论了模场相位随机起伏（相位噪音）对于测速准确度的影响,实验证实了相位噪音对激光微多普勒探测的影响,并探索出解决上述问题的方法——光纤补偿法.实验中,以输出波长为1.064 μm单块非平面环形腔激光器为光源,利用光纤补偿方法,并结合时频变换的算法,用外差探测的方式成功观测到了微多普勒频移,在传输距离为11 km时,系统最低探测速度达到了0.5 mm/s,速度分辨率达到了mm/s量级,频率分辨率达到了kHz量级,为微多普勒激光雷达的实际应用奠定了良好的实验基础.

The Methods of Decreasing the Phase Noise Influence in Micro-Doppler Ladar

With advantages of high sensitivity and more information,coherent micro-doppler laser was especially suitable for the detection of moving targets,identification of objects’ characteristics,etc.The influence of phase fluctuation in the mode field (phase noise) on velocity accuracy was discussed in two aspects including linewidth and detection distance.The experimental results validated the phase noise influence on micro-doppler detection,and a new method resolving the above problems,which called range-compensated method,was proposed.In the experimental system,the laser source was monolithic non-planar ring laser with the wavelength of 1.06 μm.The micro-doppler frequency was observed by heterodyne detection,which was processed by means of time-frequency analysis.Minimum detecting velocity of the system is 0.5 mm/s,velocity resolution reaches a level of mm/s,and frequency resolution reaches a level of kHz,when the detection distance is 11 km.The results laid an experimental foundation for the practical application of micro-Doppler ladar.