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.