Spacecraft Reentry Communication Channel Simulator Research And Design

The blackout is one of suspense in the fields of space. To solve this problem, people mainly researched from the effect of plasma sheath to electromagnetic wave and the communication system. The testing and verification of new communication technologies is essential when research communication system. Nevertheless, testing of communication system performance in the practical channel has poor stability, high cost and not repeatable. Fortunately channel simulator appeared. It greatly accelerated the communication development. But the existing channel simulators do not fully fit the reentry channel characteristic and the price is expensive. Thus the study of reentry communication channel simulator is significant.Firstly, the reasons and classification of wireless fading channel and the statistical characteristics of different types is briefly introduced in this thesis. Through the analysis of reentry channel characteristics, we select the three pathes frequency selective slow fading channels model. The spectral density function of Doppler power about two scattering path is derived. Channel model is established by rician method. Then determine the channel model parameters and simulate the wireless fading channel model with Matlab/Simulink software.Secondly, electromagnetic wave transmission characteristics of Reentry Plasma are researched. The impact of electromagnetic wave power and phase with plasma oscillation frequency and collision frequency is quantitative analysied. A plasma sheath channel model is builded by the method of curve fitting. Then connects two channels to complete the whole software channel simulator, and designs the graphical user interface based on Matlab/GUI.Finally, the overall structures and frameworks of the hardware channel simulator is designed in this paper. There has completed the design of digital down converter and base band processing module in Quartus Ⅱ software by Verilog-HDL and the timing simulation in Modelsim. The DDC is included a NCO, a CIC filter of4levels and32times extraction rate, a HB filter of3levels and8times extraction rate and a63order FIR filter. The base band processing module comprises of a flat fading channel module and a delay module.