电离层Faraday效应对远程预警雷达性能的影响

Influence of Ionospheric Faraday Effects on Detection Performance of Early Warning Radar

在对近地空间目标进行预警跟踪时,雷达发射的电磁波会在电离层中传播,电离层作为磁化等离子体,会导致电磁波产生Faraday旋转,从而对雷达探测性能造成影响。通过数值计算的方式,仿真了Faraday旋转效应导致的雷达极化失配损耗,并对仿真结果进行了分析。通过仿真结果可以看出:太阳活动高年,Faraday旋转角比太阳活动低年大;雷达工作频率越高,受Faraday旋转影响越小;目标仰角较低时,线极化失配损耗较小;椭圆极化方式下,极化失配损耗随椭圆轴比增大而增大;用圆极化方式可以最大程度地减小由Faraday旋转导致的雷达探测性能降低。

Electromagnetic waves may propagate in the ionosphere when radar is used for early warning and tracking, especially for detecting targets in the space near the earth. Since the ionosphere is magnetic plasma medium, the ionosphere may result in the Faraday rotation of electromagnetic waves, which may in- fluence the detection performance. Numeral calculation is used in this paper for simulating the polarization dis-matching loss resulted from the ionospheric Faraday effects. Many useful results can be deduced from the simulation： Faraday rotation angle is much larger during high solar activity period than moderate solar activity period; the radar operating at higher frequency is less influenced by the Faraday effects; dis-matching loss of linear polarization is less at lower elevation of target; dis-matching loss increases with the axis ratio when radar works at elliptical polarization; circular polarization can avoid the degradation of detection performance resulted from Faraday rotation.