基于分形超材料吸波体的微带天线设计

Design of a Microstrip Antenna Based on Fractal Metamaterial Absorber

基于十字分形结构,设计了一种小型化、超薄、高吸波率以及无表面损耗层的超材料吸波体。该吸波体是由两层金属及其中间的有耗介质组成,上层金属是由周期性蚀刻十字分形的贴片组成的电谐振器,下层金属不蚀刻,作为整个金属地板。通过优化结构参数,吸波体单元尺寸仅为0.13λ,厚度为0.0093λ,最大吸波率达99.6%。将此吸波体加载于普通微带天线上,制备了一种新型超材料天线。仿真和实验结果表明:相比普通微带天线,新天线在5.52~5.68 GHz工作频带内,法向RCS减缩都在3 dB以上,最大减缩量达13.5 dB,单站RCS在-18°^+18°角域减缩超过3 dB,且天线辐射性能保持不变,证实了该吸波体具有良好的吸波效果,可以应用于微带天线的带内隐身。

A metamaterial absorber with miniaturization, ultra thinness, high absorptivity rate and no surface ullage layer is designed based on cross fractal structure. The absorber is composed of two metallic layers separated by a lossy dielectric spacer. The top layer consists of etched cross fractal patch set in a periodic pattern and the bottom one is a solid metal. By optimizing the geometric parameters of the structure, its unit size is only 0.13λ, the thickness is about 0.0093λ and the absorption can exhibt 99.6%. When it is loaded on a coventional microstrip antenna, a novel metamaterial antenna is obtained. The simulation and measured results demonstate that compared with conventional antenna, the radar cross section （RCS） of the novel antenna in boresight direction is reduced by 3 dB, and the most reduction vaule exceeds 13.5 dB, the monstatic RCS reduction is over 3 dB from -18°～＋18°, while the radiation performance is kept, which proves that the absorber has an excellent ab- sorptivity and can be applied to microstrip antennas to achieve in-band stealth.