Effects of Reentry Plasma Sheath on Mutual-Coupling Property of Array Antenna

B W Bai,Y M Liu,J Xu,X P Li

doi:10.1155/2015/542392

Abstract

A plasma sheath enveloping a reentry vehicle would cause the failure of on-board antennas, which is an important effect that contributes to the “blackout” problem. The method of replacing the on-board single antenna with the array antennas and using beamforming technology has been proposed to mitigate “blackout” problem by many other researchers. Because the plasma sheath is a reflective medium, plasma will alter the mutual coupling between array elements and degrade the beamforming performance of array antenna. In this paper, the effects of the plasma sheath on the mutual coupling properties between adjacent array elements are studied utilizing the algorithm of finite integration technique. Results show that mutual coupling coefficients of array elements are deteriorating more seriously with the decrease of collision frequency. Moreover, when electron density and collision frequency are both large, plasma sheath improves the mutual coupling property of array elements; this conclusion suggests that replacing the on-board single antenna with the array antennas and using beamforming technology can be adopted to mitigate the blackout problem in this condition.

Highlights

A spacecraft reentering the Earth’s atmosphere at a hypersonic speed is enveloped by plasma fluid because of the shock wave heating of ambient gas and ablating of heat shield, causing air molecules and heat shield material dissociated and ionized [1]
Reflection coefficient property of an array element and mutual coupling characteristic between adjacent and diagonal array elements covered by reentry plasma sheath of different parameters are studied and calculated
This paper presents an approximate layered EM simulation model for the nonuniform reentry plasma sheath which obeys bi-Gaussian distributions from NASA’s report and utilizes the algorithm of finite integration technique to analyze the effects of the plasma sheath on the reflection coefficient property of an array element and mutual coupling property between array elements

Summary

Introduction

A spacecraft reentering the Earth’s atmosphere at a hypersonic speed is enveloped by plasma fluid because of the shock wave heating of ambient gas and ablating of heat shield, causing air molecules and heat shield material dissociated and ionized [1]. Performance degradations and failures of on-board antennas covered by the reentry plasma sheath have been studied by many authors for several decades. Bai [13,14,15] studies the admittance and radiation degradations of GPS and Beidou navigation patch antenna covered by reentry plasma sheath. By using beamforming technology, array antennas can provide a certain amount of gain to the communication link between the spacecraft and ground stations, and the received or transmitted RF signal strength would be increased.

Simulation Model

Results and Discussion

Conclusions