星载GNSS海洋反射信号建模与仿真

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.