电介质桁架对频率选择表面传输特性的影响

摘要

In order to analyze the influence of dielectric truss structure on frequency selective surfaces (FSS) transmission characteristics, as an example, the FSS of Y ring unit and the truss made of polyimide are investigated by the finite difference time domain method. The relevant physical model is developed and pore blocking rate is defined. Through the analysis it is proved that the variations of truss period and rib width will affect the FSS, so they become the main parameters to measure dielectric truss structure, and that the improvement of the aperture stop ratio will increase transmission loss. When truss period changes from infinity to 80 mm the transmittance of passband is reduced by more than 0.9 dB on an average; when the ribs width increases from 0 to 10 mm, the transmittance of passband is reduced by more than 0.6 dB on an average. When aperture stop ratio is lower than 12.11%, the passband produces no shipt. When aperture stop ratio is less than 4.12%, the influence of the truss on FSS is negligible. The FSS specimens is fabricated by coating and lithography process, the dielectric truss is machined by numerically controlled machine, and the microwave measurement is carried out in a dark room. The experimental results and the calculation results are verified to be in good agreement with each other. Therefore the present study presents an experimental and theoretical reference for designing the FSS stealth radar with the dielectric truss structure.%为了分析电介质桁架结构对频率选择表面（FSS）传输特性的影响, 以Y环单元的FSS和聚酰亚胺材质制备的桁架结构为例, 采用时域有限差分方法进行计算和分析. 建立物理模型并定义了孔径阻挡比P, 通过分析证明了改变桁架的周期T以及肋骨的宽度D会对FSS的传输性能产生规律性影响, 成为衡量电介质桁架结构的主要参数, 且孔径阻挡比P的提高将增加传输损耗. 当T值由无限大变为80 mm时, 通带透过率平均下降超过0.9 dB; 当D值由0变为20 mm时, 通带透过率平均下降超过1 dB. 当P值小于12.11%时通带不产生偏移现象; 当P值小于4.12%时, 桁架对FSS的影响可忽略不计. 采用镀膜和光刻工艺制备FSS试件、数控机械加工方式制备电介质桁架, 并在微波暗室中进行测量, 验证实验与计算结果相符合, 为拟采用电介质桁架结构的FSS隐身雷达罩工程应用提供了理论与实验的参考依据.