多频段十字分形频率选择表面

Multiband fractal cross dipole frequency selective surface

利用分形单元的自相似性将分形结构应用于频率选择表面(FSS)领域使单屏FSS具有多频谐振的特性,在各波段实现简易、多频带通滤波器的设计.以易加工的十字单元为例,经过递归、迭代产生二阶十字分形单元,给出描述单元几何分布的公式;应用周期矩量法结合Floquet定理及阻抗边界条件得到描述FSS表面电流分布的电场积分方程,对FSS传输特性规律进行数值分析,采用遗传算法对分形单元参数进行全局优化得到了在9.2GHz和29.4GHz谐振的单屏FSS设计;最后采用成熟的镀膜、光刻工艺制备十字分形FSS样件并在微波暗室进行FSS传输特性测试,理论与实验结果一致.

Fractal structures has self-similar properties so that they can be applied in the field of frequency selective surface（FSS） as unit cell and the fractal FSS has the nature of simple,multi-band characteristics on single layer FSS which can be used as spatial pass filters for the incident angle,polarization and the frequency of the electromagnetic wave.Take fractal cross dipole as example,which we can obtain by recursive algorithm and iterative technique,this work gives the expressions of the fractal elements＇geometry and then characterizes the FSS transmission response by the electric field integral equation for the current distribution on the single FSS screen derived from the Floquet＇s periodic theory unden impedance boundary condition.Genetic algorithm was applied to globally optimize the structure parameters in order to get the design of the double resonant FSS.Finally,FSS sample was prepared by optical lithography and measured in the anechoic chamber.Experimental results show good agreement with the calculations we made for the design of FSS with resonant frequencies 9.2 GHz and 29.4 GHz,which was what we expected from the periodic method of moment.