基于近场场图的带罩天线近副瓣畸变分析

Radome enclosed antenna proximal lobe distortion based on near-field pattern

采用FEKO软件仿真带罩天线远场方向图和近场场图,采用近场场图分析远场方向图近副瓣畸变的原因.仿真过程中采用等效源技术,兼顾仿真精度和仿真效率.带罩天线方向图近副瓣畸变主要是由天线罩尖部区造成的,近场场图表明三种效应导致近副瓣抬升:其一,电磁波经过天线罩尖部发生明显的衍射,波阵面分叉;其二,金属雨蚀头被激励出表面电流,进而产生二次辐射;其三,部分电磁波能量经反射后透过天线罩尖部区域,反射-透射电磁波能量叠加在副瓣方向上.针对上述效应,对天线罩改进设计,改进后可明显抑制带罩天线近副瓣的抬升.近场场图分析方法揭示了天线罩局部细节和远场方向图之间的联系,对天线罩电性能优化设计有很好的指导作用.

Near-field and far-field pattern of radome enclosed antenna are simulated by FEKO,and the reason of far-field pattern proximal lobe distortion is analyzed based on near-field pattern.Equivalent nearfield technique is applied in simulation process,which is precise and effective.Near-field pattern indicates three effect result in proximal lobe lifting：firstly,radome top area diffracts electromagnetic wave obviously,and wavefront bifurcates;secondly,metalic nose tip is excitated to engender surface current which causes secondary radiation;thirdly,partial electromagnetic wave reflects and then transmits through radome top area,thus reflection-transmission wave energy superposes in proximal lobe direction.Radome design is improved based on three effects mentioned above,and proximal lobe level of radome enclosed antenna is degraded obviously.Near-field pattern method reveals the relationship between radome local details and far field pattern,and is very valuable in radome electronic performance optimization.