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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.
In order to analyze the influence of dielectric truss structure on the transmission characteristics of frequency selective surface (FSS), the finite element method of finite difference time domain is used to calculate and analyze the truss structure of FSS and polyimide material of Y-ring unit.Physical model And the aperture stop ratio P is defined. It is proved that changing the period T of the truss and the width D of the truss will have a regular effect on the transmission performance of the FSS, and become the main parameter to measure the dielectric truss structure. The improvement of the aperture stop ratio P will be Increase the transmission loss.When the T value changes from infinity to 80 mm, the transmission of the passband decreases by more than 0.9 dB on average. When the value of D changes from 0 to 20 mm, the transmission of the passband decreases by more than 1 dB on average. When the P value is less than 12.11%, the passband does not shift. When the P value is less than 4.12%, the effect of truss on FSS is negligible. FSS specimen is prepared by coating and photolithography process and the dielectric truss is prepared by CNC machining. And the measurements were performed in a microwave anechoic chamber. The verification experiments are in good agreement with the calculated results, which provides theoretical and experimental references for the application of the FSS stealth radome to be used in the dielectric truss structure.