Research On The Influence Of Reentry Spacecraft Plasma Sheath On The Communication Signal

When space vehicles (such as satellite, missile, space shuttle and the reentry module of the spacecraft. etc) reentry atmosphere at hypersonic speed, a plasma sheath enveloping the spacecraft begins to come into being. The sheath is composed of plasma, and the plasma is a medium which will exert influence on communication of vehicles, such as absorption and reflection etc.According to the structure of the plasma sheath and the electromagnetic characteristics, Finite Difference Time Domain using Z-Transform method (ZT-FDTD) will be adopted to study the absorption, reflection and transmission of communication signals.At first, the formula derivation combined with the boundary condition of the plasma sheath model, based on the Maxwell equations, is executed to obtain the equations which are suitable for propagating in plasma sheath, and the equations have the property of universality.Secondly, the ZT-FDTD algorithm and the programming in VC are described in detail to calculate the coefficient of reflection and transmission, a comparative analysis between the calculation results and the results of analytical method is given in MATLAB. On this basis, ZT-FDTD is extended to the three-dimensional space to analyze the propagation of electromagnetic wave through the plasma slab.And then, the double exponential model of plasma sheath'electron is improved, which is based on the analysis of the common space vehicles, and that the signals with different frequency propagate through plasma sheath modeled by ZT-FDTD method are programmed.Finally, the communication system with the noise and the plasma sheath is realized to calculate the absorption, reflection and transmission of the signals through plasma sheath and the influence of the plasma sheath on the bit error rate of the communication system.The research work mainly embodies in the three aspects as follows:1. ZT-FDTD is extended to the three-dimensional space to realize simulating the uplink and downlink of the communication system with the incident wave added in the calculation region.2. The communication channel is modeled using the ZT-FDTD method to analyze the influence of the plasma sheath on the communication signals.3. Improve the electron double exponential model of the plasma sheath, add the model to the calculation region and realize the segmentation between the Total Field and the Scattered Field by using one-dimensional auxiliary array.