压力变化对斜入射射频波等离子鞘层极化特性的影响研究

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本文研究了压力变化对等离子鞘层斜入射射频波极化特性的影响，发表在《电磁学》领域权威期刊《IEEE Transactions on Plasma Science》第43卷第9期，2015年9月。作者Zhiwei Liu、Weinmin Bao、Xiaoping Li、Donglin Liu 和 Bowen Bai共同探讨了一个创新的方法，该方法将压缩流体湍流理论与等离子体电磁理论相结合，旨在理解等离子鞘层内的压力变化如何影响相对介电常数。研究的核心内容是通过建立一个压力变化与等离子体鞘层相对介电性质之间的联系，利用传输线类比法，对全球定位系统（GPS）频率和ka频率下斜入射的电磁波的极化特性进行了深入分析。研究发现，当电子密度低于10^18 m^-3时，压力变化对GPS频率的波极化特性有显著影响，而对ka频率的影响较小。随着入射角的增大，GPS频率下的影响增强，但随着碰撞频率和电子密度的增加，这种影响减弱。相比之下，ka频率在这种情况下更能有效缓解压力变化带来的干扰。作者强调，不同的条件会导致不同的响应，对于实际应用中的等离子体鞘层环境控制，了解这些压力变化对极化特性的影响至关重要。这项研究的结果对于卫星通信、航天器再入大气层过程中的电磁波传播以及等离子体工程等领域具有重要的理论指导意义，有助于优化设备设计，提高信号稳定性和抗干扰能力。

IEEE TRANSACTIONS ON PLASMA SCIENCE, VOL. 43, NO. 9, SEPTEMBER 2015 3147

Effects of Pressure Variation on Polarization

Properties of Obliquely Incident RF Waves

in Re-Entry Plasma Sheath

Zhiwei Liu, Weinmin Bao, Xiaoping Li, Donglin Liu, and Bowen Bai

Abstract—Synthesizing the compressible turbulent ﬂow theory

and plasma electromagnetic (EM) theory together, a novel

method connecting pressure variation and relative permittivity

of re-entry plasma sheath is developed. Using this method

and transmission line analogy, effects of pressure variation

on polarization properties of obliquely incident EM waves at

GPS frequency and Ka frequency is studied. Numerical results

indicate that effects in different conditions are various. When

electron density is lower than 10

−3

, inﬂuences of pressure

variation are obvious at GPS frequency, while Ka frequency is

feeble. For GPS frequency, effects enlarge with the increase in

incident angle, but reduce with the increase in collision frequency

and electron density. Ka frequency has more advantages on

mitigating the disturbances of pressure variations in this

situation. While in the opposite situation, inﬂuences are more

remarkable at Ka frequency. Considering that GPS wave rapidly

attenuates in the sheath when electron density is higher than

−3

and Ka wave does not, Ka frequency is an effective

way to mitigate the blackout during the re-entry process after

its shortcomings on polarization alteration have been carefully

considered.

Index Terms—Electromagnetic (EM) propagation, oblique

incidence, plasma sheath, polarization property, pressure

variation.

I. INTRODUCTION

SPACECRAFT re-entering the earth’s atmosphere

produces intense shock-wave heating and heat-shield

ablation and induces a plasma sheath enveloping it. The

plasma sheath can strongly attenuate radio frequency (RF)

waves and causes a complete loss or severe deterioration

of signals between vehicle and ground-base stations. This

phenomenon is known as the communication blackout and

often sustains several minutes. It is one of the worst situations

for tracking, telemetry, and command (TT&C) [1]. Therefore,

considerable efforts have been directed toward studying the

propagation properties of RF waves transmitting in the plasma

sheath since the 1960s [2]–[8]. These studies mainly focused

Manuscript received March 15, 2015; revised June 12, 2015; accepted

July 19, 2015. Date of publication August 18, 2015; date of current version

September 9, 2015. This work was supported in part by the National Basic

Research Program of China under Grant 2014CB340200 and in part by the

Young Scientists Fund through the National Natural Science Foundation of

China under Grant 61301173.

The authors are with the School of Aerospace Science and Technology,

Xidian University, Xi’an 710126, China (e-mail: milianpanduola@sina.com;

xiaobin60@sina.com; xpl@xidian.edu.cn; donglinliu@stu.xidian.edu.cn;

bwbai@stu.xidian.edu).

Color versions of one or more of the ﬁgures in this paper are available

online at http://ieeexplore.ieee.org.

Digital Object Identiﬁer 10.1109/TPS.2015.2461546

on the vertical incident waves. In real situations, waves usually

obliquely propagate through the plasma sheath and received

by the onboard antennas.

Recently, Cheng and Liu [9] discussed the effects of incident

angle on the propagation characteristics for both parallel-

polarized and perpendicular-polarized waves in inhomoge-

neous plasma and found that discrepancies exist between

the transmission properties of the two polarized waves.

Bai et al. [10] discussed the polarization properties of waves

that obliquely propagate in plasma sheath and found that

the larger the incident angle and the lower the collision

frequency is, the worse the deterioration of the polarization

property. In all these research studies mentioned above, plasma

is considered a steady dielectric medium. However, ﬂow in

re-entry conditions is unsteady [11], [12], and parameters of

plasma sheath such as pressure is varying. This induces the

variation of its dielectric properties. Thus, the polarization

properties of RF waves would change.

However, the effects of pressure variation on polarization

properties of RF waves that obliquely incident in the plasma

sheath have not been given much attention. Therefore, this

paper attempts to build a connection between the pressure

variation amplitude and the plasma dielectric properties. Using

this method, effects of pressure variation on polarization

properties could be estimated. This paper takes right-hand cir-

cular polarization (RHCP) wave and RHCP receiving antenna

as an example to study the effects at GPS frequency and

Ka frequency in various plasma conditions. The remainder

of this paper is organized as follows. Section II studies the

relation between the pressure variation amplitude and the

plasma relative permittivity. Section III introduces the physical

model and numerical calculation method used in this paper

and polarization properties that will be analyzed. Section IV

analyzes the polarization properties of RHCP waves

of GPS frequency and Ka frequency receiving by an

RHCP antenna. Section V provides the conclusion.

II. R

ELATION BETWEEN PRESSURE VARIATION

AMPLITUDE AND PLASMA RELATIVE PERMITTIVITY

As plasma is lossy medium, its relative permittivity is

critical for electromagnetic (EM) wave propagation problems.

Considering that electron density is a basic parameter for

plasma and inﬂuences the relative permittivity directly, this

paper takes the electron density as the link between relative

permittivity and pressure variation amplitude.

See http://www.ieee.org/publications_standards/publications/rights/index.html for more information.

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