Abstract

To enhance the radiation performance of the Beidou antenna in the near-space hypersonic vehicle, the static strong magnetic field is used to weaken the electron density in plasma surrounding the antenna. In order to demonstrate the effect of this program, a time-domain multi-physical method is proposed. In the proposed method, what is first analyzed is the reduction of electron concentration in plasma sheath by static strong magnetic field with the spectral element time domain (SETD) method, which has spectral accuracy. Then, the electron density after mitigation is extracted to replace the original electron concentration around the antenna. Hence, the distribution of the manipulated plasma sheath can be obtained. Finally, the radiation characteristics of BeiDou antenna installed in the vehicle are analyzed by the conformal finite difference time domain (CFDTD) method. The simulation results exhibit radiation patterns under different conditions. With the plasma sheath, the radiated electromagnetic waves are greatly attenuated, which will significantly affect the transmission of communication signals. Importantly, the radiation patterns are effectively improved with the external static magnetic field, confirming that it provides an effective tool to mitigate the influence of plasma sheath on the radiation performance of antenna in hypersonic vehicle.

Highlights

  • In order to demonstrate the effect of this program

  • The proposed method firstly analyzes the reduction of electron concentration in plasma sheath

  • the radiation characteristics of BeiDou antenna installed in the vehicle are analyzed with the conformal finite difference time domain

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Summary

Introduction

摘 要 为了增强临近空间超高声速飞行器中的北斗天线的辐射性能,采用 了施加静态强磁场削弱特定区域等离子体电子密度的方案,开展多物理场时域建 模分析方法研究。首先利用具有谱精度的时域谱元(SETD)法对静态强磁场作用 下等离子鞘套中北斗天线周围电子浓度的削减程度进行分析,再利用共形时域有 限差分(CFDTD)方法对临近空间高超声速飞行器的北斗天线辐射特性进行建模 仿真分析。本文所提方法预测了真实流场空间中静态强磁场对飞行器中北斗天线 辐射性能的影响。仿真结果表明,施加静态强磁场能够对电子浓度起到“吹散” 作用,从而提升等离子鞘套中北斗天线的辐射性能,为减弱等离子鞘套对临近空 间高超声速飞行器中北斗天线辐射性能的影响提供理论指导。 基金: 国家自然科学基金(批准号:62025109, 62001231, 61931021),电磁环境效应国家 重点实验室稳定资助项目(批准号:JCKYS2019 DC4),中国空间技术研究院重点实验室稳 定支持基金(批准号:2020SSFNKLSMT-12)和江苏省自然科学基金(批准号:BK20200467) 资助的课题. 为了缓解“黑障”现象对电磁波传播质量的影响,国内外研究学者进行了大 量的研究,主要提出的方法从飞行器结构特性和电磁波特性两方面出发。结构特 性主要从优化飞行器气动外形【6】、改进飞行器涂覆材料【7】的角度出发来减弱飞行 器高速运动过程中与周围气体的摩擦碰撞或使得烧蚀后的材料产物能够与等离 子体中电子产生复合或其他效应以减少等离子体浓度。电磁特性方面的方法较多, 主要有改变电磁波频率【8-9】、增大天线发射功率【10】、强加强磁场和交叉电磁场【1112】。首先,改变电磁波频率主要是使通信频率高于等离子频率或远低于等离子频 率和碰撞频率来减少电磁波穿过等离子体时的衰减,但频率过高难以实现远距离 传输,而频率过低则会大大增加天线的尺寸,侵占更多飞行器空间。增大天线发 射功率是最直观的一种方法,但这会对天线的发射和接收性能提出严峻考验【13】。 综合考虑下来,施加强磁场或交叉电磁场是较为有效的实现形式,这两种方法通 过洛伦兹力和电场力来使得电子向某一特定的方向运动,从而在反方向产生一块 电子浓度较低的区域【14-15】,在该区域安置天线来实现通信。若要产生强恒定电场 需要较大的电源进行供电,而随着超导技术的快速发展【16】,施加静态强磁场缓解 “黑障”效应的技术越来越成为可能。

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