Abstract
Communication blackout caused by the plasma sheath surrounding hypersonic vehicles is a serious threat to the safety of hypersonic vehicles. Terahertz (THz) communication is considered to be a potential solution to the blackout problem. However, hypersonic plasma sheaths can affect not only electromagnetic wave propagation, but also the radiation performance of onboard antennae. Therefore, it is necessary to investigate the radiation performance of THz antennae in hypersonic plasma sheaths. In the present study, the impact of vehicle shapes (blunt-coned and sharp-coned vehicles) on plasma sheaths was investigated numerically. The antenna involved in the present study was a 0.14 THz array antenna. The antenna performance was compared with the aspects of mainlobe gain, mainlobe direction, and mainlobe width. The present study shows that both sharp-coned and blunt-coned plasma sheaths are inhomogeneous. Nevertheless, their structures are obviously different. Such differences yield different antenna performance in sharp-coned and blunt-coned plasma sheaths. Compared with sharp-coned plasma sheaths, blunt-coned plasma sheaths can refract antenna radiation direction, which can result in worsened communication quality in the expected direction. In addition, the phenomena are discussed in detail. Suggestions of vehicle shape design to guarantee communication quality in hypersonic flight missions are proposed.
Highlights
Hypersonic vehicles in near space fly over the speed of Mach five, which is five times the speed of sound [1]
Previous research has revealed that the plasma sheath can impact the electromagnetic wave propagation, which can result in antenna performance changes
The results reveal that the sharper vehicle can lead to a smaller plasma sheath thickness and less impact on antenna performance
Summary
Hypersonic vehicles in near space fly over the speed of Mach five, which is five times the speed of sound [1]. Some previous studies reveal that the parameters of the plasma sheaths depend on many factors, e.g., atmospheric conditions [12], flight speed [8], angle of attack [13], and the shape of the vehicle [14], in which case antenna performance is affected. EHF array antenna performance in plasma sheaths corresponding to different vehicle shapes are rarely investigated. A method of replacing an on-board single antenna with an array antenna and using beamforming technology has been proposed by researchers to mitigate the problem [15]. A 0.14 THz array antenna and plasma coupling models were established to obtain the detailed influence of vehicle shape on the antenna performance. Suggestions of vehicle shape design to guarantee communication quality in hypersonic flight mission are proposed
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