Navigation antenna performance degradation caused by plasma sheath

Abstract

A plasma sheath generated around a hypersonic vehicle can be a serious obstacle to fixed-frequency 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.

Acknowledgment

This work was supported by the National Natural Science Foundation of China under Grant Nos. 61,003,196 and No. 61,105,066, and by the Fundamental Research Funds for the Central Universities under Grant Nos. K50510040004 and K50510040007.