Theoretical Study on the Impacts of Time-Varying Reentry Vehicles Plasma Sheath on the Terahertz Array Antenna Performance

The communication blackout used to occur on reentry vehicles in near space. Previous studies in recent years have shown that terahertz (THz) communication is a potential solution to the blackout problem. Most previous studies consider the plasma sheath surrounding the reentry vehicle as a static plasma layer, although the plasma sheath always keeps evolving. In such a case, the impact of time-varying and inhomogeneous plasma distribution on the performance of vehicle antennas was rarely investigated. In this study, a plasma sheath evolution model for reentry vehicles was developed, and the evolution of the plasma sheath was obtained via numerical solution. In addition, a THz array antenna was introduced in order to investigate the effect of time-varying plasma sheath on antenna performance. The results indicate that during the reentry process of the vehicle, the antenna gain, antenna directivity, and antenna return loss vary dynamically and drastically. The performance of the onboard antenna during the reentry process is unstable, which affects the performance of the vehicle communication system. Finally, the mechanism of antenna performance variation is analyzed, and the corresponding optimization scheme to ensure the antenna performance in the plasma sheath is discussed. The present study is helpful in understanding the complexity of electromagnetic propagation in a self-consistently changing reentry plasma sheath.