共享孔径人工电磁媒质设计及其在高增益低雷达散射截面天线中的应用∗

摘要

提出了一种具有部分反射特性和吸波特性的共享孔径人工电磁媒质(shared aperture metamaterial, SA-MTM).该媒质由上层斜十字金属图案加载集总电阻的吸波表面、下层开条带缝隙金属面的部分反射表面以及中间介质层构成,吸波表面和部分反射表面在垂直维度上共享了一个物理孔径使该媒质同时实现了吸波特性和部分反射特性.将SA-MTM与天线一体化设计,利用SA-MTM的部分反射表面和天线表面构成的法布里-珀罗(Fabry-Perot, F-P)谐振腔提升天线的增益,利用SA-MTM的吸波表面吸收入射电磁波实现低雷达散射截面(radar section cross, RCS)天线的设计.仿真和实验结果表明, SA-MTM 的加载使天线的前向增益在5.57—5.94 GHz 的工作带宽范围内都提升了3 dB以上,且天线的后向RCS在2—9 GHz范围内都有明显的减缩.该研究成果克服了天线辐射性能和散射性能无法兼顾的矛盾,对高增益低RCS天线的设计具有重要的指导意义.%A shared aperture metamaterial (SA-MTM) with partially reflection and absorber characteristics is presented. The SA-MTM is composed of two metallic layers separated by a dielectric spacer;the top absorbing surface (AS) consists of oblique cross metallic pattern loaded with lumped resistances, and the bottom partially reflecting surface (PRS) consists of etched parallel slots in a metallic layer. An SA-MTM with partial reflection and absorption characteristics is fulfilled by making the absorbing surface and partially reflecting surface shared the same aperture in the vertical direction. The SA-MTM is applied to the waveguide slot antenna; the Fabry-Perot resonance cavity constructed by the PRS and the metallic ground layer of the waveguide slot antenna can achieve high gain, while the AS can obtain the low radar cross section (RCS) characteristic antenna by absorbing the incident wave. Simulation and experimental results demonstrate that the antenna with SA-MTM gain is enhanced above 3 dB in the operation frequency range, the backscattering RCS is obviously reduced in a frequency range of 2—9 GHz. This idea can help us design a high gain and low RCS antenna, which overcomes the conflict between scattering and radiation performance of antenna.