本文为丹麦技术大学（作者：Petter Lindelöw）的博士论文，共187页。

本文对相干激光雷达用于风场遥感进行了研究。当桅杆式风速计因经济或实际原因而无法使用时，遥感测风是非常重要的。其中一个重要的领域是在风能领域，在离地面几百米的距离上进行精确的风力感应，对于现场评估、涡轮机功率验证以及未来的应用（如主动叶片变桨和负载控制以获得最佳输出）非常重要。相干激光雷达可以探测到收集的微弱光线中很小的频率变化。因此，远程探测风场的一个可行解决方案是感测悬浮在大气中气溶胶散射接收光的多普勒频移。

基于光纤的系统具有成本效益和健壮性，并且可以在没有安全限制的情况下运行；因此，它们是非科学应用的理想选择。本论文涉及的领域很广，回顾了相干激光雷达风传感器的研究现状，扩展了信号模型，给出了商用激光雷达的应用研究结果，以及调频原型的开发和评估。通过考虑距离选通系统的距离相关持续时间，扩展了相干激光雷达探测离散目标的标准模型，该模型对窄带信噪比描述和采样体积权重有显著影响。建立并验证了聚焦光纤激光雷达的距离相关收集效率模型。这些进展对于预测激光雷达性能和优化信号处理具有重要意义。

在本研究中发明了一种新颖的频率调制概念。该技术基于等距频率步进脉冲串和频率跟踪本振。它在高脉冲重复频率下工作，尽管如此，它将避免常规的缺点：距离模糊和传感范围的限制。这一新的概念可以提供更精确的系统，同时避免使用高峰值功率，因为峰值功率会引入受激布里渊散射和非线性效应，并对发射机中的其他组件提出更高的要求。设计并评估了一种适用于本发明调频技术的扫频器。随后利用该扫频器对连续波激光雷达进行了调频原型机改装和原理验证活动，验证了新技术的优点和局限性。对从两个不同商业系统收集的风数据进行的应用研究表明，当由聚焦连续波系统感测时，风分布谱的权重受具有非典型长相关散射持续时间的单个粒子的影响；当被聚焦距离选通系统感知时，受与距离相关的收集效率影响。

In this thesis a study of coherent lidars for remote wind sensing is undertaken. Remote wind sensing is important when mast mounted anemometers cannot be used due to economical or practical reasons. One such important field is within the wind energy sector where accurate wind sensing at distances of up to a few hundred meters from the ground is important for site evaluation, turbine power verification and for future applications such as active blade pitch and load control for an optimized output. Coherent lidars can detect very small frequency variations in collected weak light. A viable solution to remotely sense wind is thus to sense the Doppler shift induced on the received light scattered off aerosols suspended in the atmosphere. Fiber based systems are cost effective and robust, and can operate without safety restrictions; they are thus an ideal choice for non-scientific applications. The thesis covers a wide field; the state of the art coherent lidar wind sensors is reviewed, the signal model is expanded upon and results of applied research on commercially available lidars, as well as the development and evaluation of a frequency modulated prototype, are presented. The standard model for coherent lidars sensing dispersed targets was expanded upon by considering the range dependent correlated contribution duration of range gated systems, which significantly affects the narrowband signal to noise description and the weighting of the sample volume. A model of the range dependent collection efficiency obtained by focused fiber based lidars has been developed and verified. These advancements are important for predicting the lidar performance and optimizing the signal processing. A novel frequency modulation concept, which is promising for the remote sensing of wind, was invented in this study. The technique is based on equidistantly frequency stepped pulse trains and a frequency pursuing local oscillator. It operates at high pulse repetition but will despite this avoid the customary disadvantages; range ambiguity and a limitation of the sensing range. This novel concept could provide more accurate systems while avoiding the use of high peak powers which introduces stimulated Brillouin scattering and non-linear effects as well as putting higher demands on other components in the transmitter. A frequency sweeper, appropriate for the invented frequency modulation technique, was constructed and evaluated. This sweeper was subsequently used to modify a continuous wave lidar into a frequency modulated prototype and a proof of principle campaign, demonstrated the merits and limitations of the novel technique. Applied investigations of wind data collected from two different commercial systems revealed that the weighting of the wind distribution spectrum is influenced by single particles with atypically long correlated scatter durations, when sensed by focused continuous wave systems, and by the range dependent collection efficiency, when sensed by focused range gated systems.

1.       基于相干激光雷达的风遥感简介

2. 相干激光雷达

3. 频率调制的相干激光雷达

4. 步进频脉冲串发生器

5. FSPT调制的激光雷达

6. 与风切变成比例的激光雷达测量偏差

7. 光纤相干激光雷达用于风场遥感的结论

附录A 激光相干性

附录B 大气相关持续时间

更多精彩文章请关注公众号：