水平层状介质中电磁场并矢Green函数的一种快速新算法

本文利用提取直射波并结合自适应数字滤波等技术提出一种计算水平层状介质中电磁场并矢Green函数的快速算法. 首先将谱域Green函数中表征均匀介质作用的直射波提取出来并对其积分进行解析计算,这种处理降低了谱域Green函数的奇异性,可在很大程度上缩短其积分收敛区间. 然后在将谱域Green函数剩余部分对应积分转化为三个快速下降积分的基础上,引入一种自适应数字滤波算法对其进行快速求解. 最后通过具体算例验证了本文所述算法的有效性. 关键词： 并矢Green函数 快速算法 水平层状介质     

Frequency selective surface structure optimized by genetic algorithm

Frequency selective surface (FSS) is a two-dimensional periodic structure which has prominent characteristics of bandpass or bandblock when interacting with electromagnetic waves. In this paper, the thickness, the dielectric constant, the element graph and the arrangement periodicity of an FSS medium are investigated by Genetic Algorithm (GA) when an electromagnetic wave is incident on the FSS at a wide angle, and an optimized FSS structure and transmission characteristics are obtained. The results show that the optimized structure has better stability in relation to incident angle of electromagnetic wave and preserves the stability of centre frequency even at an incident angle as large as 80°, thereby laying the foundation for the application of FSS to curved surfaces at wide angles.     

The effect of a non-aligned unit on double-screen frequency-selective surface transmission characteristics

Double-screen frequency-selective surfaces (FSSs) can bring about a better flattened effect and a rapidly declining edge. They are therefore an effective means to achieve outer-zone stealth of the radar cabin to detect radar waves. In this article, a double-screen wide-bandpass FSS structure is designed and the transmission characteristics of the units under alignment and non-alignment are simulated by means of the spectral domain approach. Meanwhile, the experimental parts fabricated by vacuum evaporation and lithography are tested in a microwave chamber. The results show that the aligned unit structure has good incident angle stability and can achieve high transmittance when the bandwidth is 3.3 GHz, and the transmission loss is less than 1 dB. When the units have a non-aligned structure, the bandwidth decreases and transmission loss increases with increasing incident angle.     

Influence of substrate process tolerances on transmission characteristics of frequency-selective surface

Frequency-selective surface(FSS)is a two-dimensional periodic structure consisting of a dielectric substrate and the metal units(or apertures)arranged periodically on it.When manufacturing the substrate,its thickness and dielectric constant suffer process tolerances.This may induce the center frequency of the FSS to shift,and consequently influence its characteristics.In this paper,a bandpass FSS structure is designed.The units are the Jerusalem crosses arranged squarely.The mode-matching technique is used for simulation.The influence of the tolerances of the substrate's thickness and dielectric constant on the center frequency is analyzed.Results show that the tolerances of thickness and dielectric constant have different influences on the center frequency of the FSS.It is necessary to ensure the process tolerance of the dielectric constant in the design and manufacturing of the substrate in order to stabilize the center frequency.     

圆环单元FSS对改善吸波体雷达吸波特性的影响

设计了圆环单元的频率选择表面（FSS）结构,并将该结构置于吸波材料中构成了复合吸波结构。利用谱域法对该结构进行数值模拟,计算出频率为2～16GHz微波波段的反射系数,并研究了圆环单元尺寸和排布周期对其吸波特性的影响。结果表明：当圆环单元FSS的单元间距为10mm,单元尺寸为3．3mm时,其共振频率的反射率由-8．15dB降低为-14．54dB,-5dB吸波带宽由1．2GHz拓展为3．05GHz;且随圆环单元尺寸增大,共振反射率增加;随单元排列周期增加,吸波材料带宽增大。结果表明,利用FSS可以明显改善吸波材料涂层的吸波性能,通过凋整相关参数可以获得所需的复合吸波结构,拓展FSS在吸波材料中的应用范围。