星载GNSS海洋反射信号建模与仿真

星载GNSS反射信号建模与仿真对GNSS反射信号正逆问题的研究及接收机算法和性能的评估非常重要。从几何、信号和信息的角度建立了星载GNSS反射信号分层建模方法。详细论述了星载GNSS反射信号的双基几何关系，建立了海风、涌浪和降雨驱动的线性组合海浪谱，并基于此计算了GNSS反射信号双基散射系数，基于各散射单元独立散射的假设推导了反射信号模型，通过仿真产生了星载GNSS反射信号及时延-多普勒相关功率，并与UK TDS-1卫星实测相关功率进行了对比分析。结果显示，通过先产生反射信号后处理得到的相关功率和直接端对端产生的相关功率与UK TDS-1卫星实测的相关功率的余弦相似度分别为0.97和0.94，所提架构和方法可正确对星载GNSS反射信号进行建模和仿真。同时，通过所建平台分析了涌浪和降雨形成的海浪谱对星载GNSS反射信号的影响。结果发现，涌浪主要影响低风速探测而对高风速无影响，降雨对星载GNSS反射信号无明显影响。 

Modeling and simulation of spaceborne GNSS ocean-reflectometry

The modeling and simulation of spaceborne GNSS reflectometry is important for the research of forward and inverse problem of GNSS reflectometry, and the evaluation of algorithm and performance in the receiver. This paper firstly develops the layered structure of modeling spaceborne GNSS reflectometry from the perspectives of geometry, signals and related power. Secondly, the bistatic geometry of spaceborne GNSS reflectometry is discussed in detail. Thirdly, the sea spectrum is developed by linearly combining wind-, swell- and rain-driven sea spectrum, and further bistatic scattering coefficient is computed. Fourthly, based on the assumption that scattered signals from each scattering unit are independent, an ocean-reflected GNSS signal model is derived. Finally, the ocean-reflected GNSS signals and delay-Doppler maps are produced by simulation, and are analytically compared to the measured correlation power from UK TDS-1. The results show the simulated delay-Doppler maps obtained through end-to-end simulating correlation power and through processing simulated GNSS signal have the cosine similarity of 0.97 and 0.94 with the measured delay-Doppler maps from UK TDS-1 respectively, so that proposed approach could be used to simulate correctly reflected GNSS signals and delay-Doppler maps through comparing the simulated delay-Doppler maps and actual ones received from UK TDS-1. In addition, the simulation analysis of the influence of swell and rain on the reflected GNSS signals shows that swell mainly impacts reflected GNSS signal for low wind speed and does not impact it for high wind speed, and rain has no significant influence on the reflected GNSS signal.