北斗信号沙漠回波特性及陕北沙地参数反演算法研究

沙漠探测关系到国家对沙漠治理情况的掌握和防沙治沙的安排部署，将北斗导航卫星信号作为波源探测陕北沙漠属于地物探测新的着眼点。项目基于GNSS-R探测理论和多径回波分析及处理方法，研究利用北斗导航L波段信号进行陕北沙漠构性和沙丘状态探测的反演识别问题。根据沙漠对北斗信号作用，探索弱回波信号提取算法，以介电系数和反射率为桥梁，建立反射信号参数（极化特性、振幅、相位和频率等）与沙漠湿度变化率、沙表温度的关系；理论结合原理性实验，开展多基、多点、双频测试的实验研究，仿真分析沙尘、风场和光照条件等因素对北斗回波的影响，阐明测试手段上的宏观几何关系对微观几何关系的影响机制；建立沙漠物理构性与沙丘状态的探测模型，研究不同特质沙漠分布区域的界定和描绘方法。该研究为北斗系统地物识别的拓展应用奠定理论基础，对揭示微波信号的沙漠散射规律有重要意义。

Desert exploration plays an important role in our national desert-control strategic plan, and will support the state to understand and monitor the desert situations. It is a new focus of geophysical exploration to take the signal of Compass navigation satellite as the survey wave source to explore the desert of Northwest of Shaanxi province (Shan-bei). Based on the theory of GNSS Remote Sensing and Multipath echo analysis and processing, and by using Compass navigation L-band signals, an inversion analysis is conducted to explore the Shan-bei desert texture and dunes status. The project is also trying to build up the mathematical model to extract the weak echo signals based on the reaction of the desert to the signal of Compass navigation satellite. Following steps are found out the dielectric coefficient and reflectance as the bridge to set up the internal relationship between the parameters of the reflected signals (Polar characteristics, Amplitude, phase and frequency etc) and the desert moisture change rate and surface temperature. Combine the principle experiment with the theory to carry out an experimental study of applying methods on to multi locations, multi object points and double frequencies tests, simulate the key factors such as sand-dust, wind, and light conditions, and analyze the effects of these factors on the echo of Compass navigation system, to expound the mechanism that how the macro geometry will influence the micro geometry with different test methods, and set up the exploration model of desert texture and dunes status to study the approach to defining and mapping the desert distribution area per different desert texture. This study will sets up the theoretical base for expanding the application of Compass navigation satellite to the identification of ground features, and it is significant to reveal the scattering law of microwave signal in desert.