基于近场场图的带罩天线近副瓣畸变分析

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.

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

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.