Navigation antenna performance degradation caused by plasma sheath

Abstract

A plasma sheath generated around a hypersonic vehicle can be a serious obstacle to fixedfrequency communications, especially navigation systems. This paper studies the effects of a plasma sheath on a Beidou navigation circular microstrip patch antenna. The dynamic stratified medium model method, which is based on the gradient of electron density profile curve, is employed to model the nonuniform plasma sheath. Using the algorithm calculation of the time-domain finite integration, the navigation antenna radiation pattern property is obtained, along with the changes in the reflection coefficient and input impedance properties. Results show that antenna pattern distortion, resonant frequency shift, and impedance mismatch caused by plasma are proportional to the electron density. The process of reentry blackout is also reproduced from the perspective of the antenna performance degradation. The inductor L and capacitor C (LC tuning circuit) impedance mismatch compensation scheme proposed is demonstrated to be effective and it can decrease return loss by 19.4 dB under the most serious plasma environment, thus reducing signal reflection and enhancing navigation system performance.

Dynamic Selection of Relay Node Based on Channel Fading Coefficient for Reentry Hypersonic Vehicles

“…The collision frequency distribution is difficult to measure, and thus an approximation value is usually required. Figure 4 shows the typical collision frequency of a RAM-C III vehicle with altitudes and temperatures [11,22] typical temperature of 2000 K is adopted to obtain the typical collision frequency. The peak collision frequency varies from 7 MHz at 76 km to the extreme 24 GHz at 21 km.…”

“…However, the plasma sheath can be approximately modeled by several adjacent homogeneous thin plasma slabs according to the electron density distribution profile [22]. To achieve excellent computation accuracy and prevent a superabundant calculated amount, the electron density discrepancy between adjacent thin plasma slabs is limited < 10% [23].…”

“…The thickness of each layer is non-uniformly divided according to the distribution of electron density and may differ largely according to the electron density gradient. The more the stratification numbers are and the thinner the slab width is, the larger the gradient (electron density changes drastically); otherwise, the slab width becomes thick with a few stratification numbers [22]. The EM waves propagating in the N-layered plasma along the z-axis can be equivalent to the cascade of the transmission lines with different impedances, and the transmission coefficients of the N-layered plasma model can be determined by the transmission line analogy method.…”

Channel Characterization and Finite-State Markov Channel Modeling for Time-Varying Plasma Sheath Surrounding Hypersonic Vehicles

“…There have already been many researches dealing with the plasma sheath and investigating its effects on the communication signals [6][7][8][9][10][11][12][13]. However, most of the previous works consider this problem in a time-invariant case, where severe amplitude attenuation and large phase shift are reported [6][7][8][9][10].…”

“…However, most of the previous works consider this problem in a time-invariant case, where severe amplitude attenuation and large phase shift are reported [6][7][8][9][10]. Although these steady-state effects are very important, the time-varying effects are also very crucial for communication failure and this has rarely been studied.…”