EHF Wave Propagation in the Plasma Sheath Enveloping Sharp-Coned Hypersonic Vehicle

The plasma sheath, which is the weakly ionized gas layer that envelopes hypersonic vehicles in near space, could shield communication signals and yield communication blackout. In the recent couple of decade, the extremely high frequency (EHF) communication is being considered as a potential solution to the blackout problem. On the other hand, previous studies used to focus on the EHF wave propagation in idealized plasma slabs or plasma sheaths covering blunt-coned vehicles. In the present letter, the plasma sheath enveloping sharp-coned hypersonic vehicles was modeled. The characteristics of EHF wave propagation in the sharp-coned plasma sheath were investigated. According to the study, the maximum electron densities and electron collision frequencies in sharp-coned plasma sheath is in the same magnitude of that in blunt-coned plasma sheath. However, the thickness of sharp-coned plasma sheath is much lower than that of blunt-coned plasma sheath. In addition, the power transmission rate at the frequencies of 140 and 225 GHz is high enough to afford communication tasks. Moreover, the reflection plays important roles in the energy loss of EHF wave propagation in sharp-coned plasma sheath, whereas the reflection in blunt-coned plasma sheath is ignorable. According to the analysis, the reason for such difference is that the gradient of relative permittivity in sharp-coned plasma sheath is larger than that of blunt-coned plasma sheath, which yields significant reflection to the EHF waves.