In this work we propose a system of two frequency-selective surfaces (FSSs) with an ultra-wide band-stop response for 5G millimeter-wave applications. The analyses are based on the equivalent circuit method, which predicts the transmission characteristics for a plane wave with normal and oblique incidence, and the scattering matrix technique, which provides the result of the cascaded structure. The geometries used in the single-layer FSSs are simple to design, and a series of basic equations are described in order to calculate the inductance and capacitance of conducting strips. FSSs prototypes were fabricated and measured in an anechoic chamber. The first FSS is shaped with the four-arms star geometry, which has a resonant frequency at 27.92 GHz for both measured and simulated results. The second FSS is based on the quasi-square geometry, whose resonant frequency for the experimental and numerical results are 35.68 GHz and 35.76 GHz, respectively, for the transverse electric polarization. These two single-layer FSSs present theoretical resonant frequency at 28 GHz (FSS #1) and 35.8 GHz (FSS #2). Cascading of the two FSSs was realized by using an air gap whose effect was analyzed. A gap space in the order of about $\lambda /4$ matched with the predicted resonant frequency of the individual structures. Numerical and measured results show excellent agreement with a maximum error of 1.03%. All measured results closely follow those of simulated ones, thus validating the design approach and applications.

中文翻译：

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使用等效电路模型为 5G 毫米波应用设计超宽带阻频率选择表面

在这项工作中，我们提出了一个由两个频率选择表面 (FSS) 组成的系统，该系统具有超宽的带阻响应，适用于 5G 毫米波应用。分析基于等效电路法（预测具有垂直和倾斜入射的平面波的传输特性）和散射矩阵技术（提供级联结构的结果）。单层 FSS 中使用的几何形状设计简单，并且描述了一系列基本方程以计算导电条的电感和电容。FSS 原型是在消声室中制造和测量的。第一个 FSS 采用四臂星形几何形状，测量和仿真结果的谐振频率为 27.92 GHz。第二个FSS基于准正方形几何，对于横向电极化，其实验和数值结果的谐振频率分别为 35.68 GHz 和 35.76 GHz。这两个单层 FSS 的理论谐振频率分别为 28 GHz (FSS #1) 和 35.8 GHz (FSS #2)。两个 FSS 的级联是通过使用一个气隙来实现的，并分析了气隙的影响。大约的间隙空间 $\λ/4$与各个结构的预测共振频率相匹配。数值和测量结果显示出极好的一致性，最大误差为 1.03%。所有测量结果都与模拟结果密切相关，从而验证了设计方法和应用。