相干测风激光雷达微弱信号的频率估计

相干测风激光雷达通过探测大气气溶胶的多普勒频移信息获取风速信息。其回波信号为微弱信号，微弱信号中频率提取属于频率估计范畴。经补零处理后的快速傅里叶变换算法（补零FFT算法）应用于相干测风激光雷达频率估计，具有算法简单，运算速度快，稳定性高等优点。与常用的频率估计算法脉冲对算法（PP算法）和改善型脉冲对算法进行比较，验证了补零FFT算法在相干测风激光雷达微弱信号频率估计方面的明显优势。通过仿真软件MATLAB仿真非相参积累脉冲3 000次的前提下检测微弱信号（距离门宽度为128采样点）信噪比可达-26.6 dB。最后，通过风场试验获取实测风速数据，验证了补零FFT算法在相干测风激光雷达中应用的优越性。

Frequency estimation of the weak signal of the Coherent Wind Lidar

Coherent Wind Lidar can obtain the atmospheric wind velocities through measuring the frequency shift of laser back from the atmospheric aerosol caused by Doppler effect. The scattered energy propagating back toward the receiver is very weak. So the frequency extraction from the weak signal belongs to the field of frequency estimation. The zero-padding Fast Fourier Transform(FFT) algorithm applied to the frequency extraction of the Coherent Wind Lidar has the advantage of algorithm simplicity, fast operation and high stability. Compared with the pulse-pair(PP) algorithm and the improved PP algorithm, zero-padding FFT algorithm was validated to have an obvious advantage in processing weak signal of Coherent Wind Lidar. In addition, the simulation with MATLAB shows that the measurable SNR of the weak signal can reach -26.6 dB by using the zero-padding FFT algorithm in the condition of 3 000 pulses non-coherent integration (128 samplings in one range gate). At last, the wind velocity test data gotten by the Coherent Wind Lidar was processed by improved PP algorithm and the zero-padding FFT algorithm, and through the processing results gotten by two algorithms, the advantage of zero-padding FFT algorithm is verified the advantage again.