随着超表面技术的发展，其在无线通信和电磁隐身领域有着广泛的应用。电磁超表面通过调控电磁波的极化、振幅和相位，实现对电磁波的灵活控制。本文针对反射电磁超表面的波束调控及其应用展开研究，分别设计了基于几何相位和传输相位的编码超表面，实现了不同方向的波束调控，所设计的超表面可以降低雷达散射截面，提高电磁隐身性能。

(1) 设计了一个宽频、高效率的极化器，该极化器在6.9-14.5 GHz内能够实现线极化波的正交极化转换和圆极化波的共极化转换，极化转换率均大于0.9，相对带宽达到71%。通过调控几何相位以得到不同编码单元，将其在x或y方向以周期形式排列，实现不同方向的波束调控。当线极化波垂直入射时，编码超表面在6-16 GHz内的雷达散射截面值低于10 dBsm，相比金属平面缩减了20 dB。采用自由空间法对样品进行了实验测试，实验结果与仿真结果一致。

(2) 设计了一个四叶玫瑰型反射超表面，当线极化波垂直入射时，该超表面在8-14 GHz内的反射系数大于0.96，通过改变玫瑰叶长可实现传输相位在0-360°全覆盖。利用遗传算法对超表面进行编码和优化，以实现任意方向的波束调控。结果表明，遗传算法可以有效地优化编码超表面阵列。编码超表面在7.9 GHz和10.1 GHz的雷达散射截面值分别为-10 dBsm和-13 dBsm，相比金属平面缩减了12.7 dB和17.6 dB。采用自由空间法对样品进行了实验测试，实验结果与仿真结果一致。

研究结果表明，本文所设计的超表面可以实现线极化波和圆极化波的波束调控，并降低雷达散射截面，在波束调控和电磁隐身方面具有一定的应用价值。

Metasurface is widely used in wireless communication and electromagnetic stealth with the development of metasurface technology. It achieves flexible control of electromagnetic waves by modulating their polarization, amplitude and phase. In this paper, the beam control of reflective electromagnetic metasurfaces and their applications are investigated. The coding metasurfaces based on geometric phase and transmission phase are designed respectively to achieve beam control in different directions, and the designed metasurfaces can reduce the radar scattering cross section and improve the electromagnetic stealth performance.

Firstly, a wide-band, high-efficiency polarizer is designed, which can achieve orthogonal polarization conversion of linearly polarized waves and co-polarization conversion of circularly polarized waves in 6.9-14.5 GHz, with a polarization conversion rate greater than 0.9 and a relative bandwidth of 71%. The beam control in different directions is achieved by modulating the geometric phase to obtain different coding units, which are arranged in the x or y direction in a periodic pattern. The radar scattering cross section of the coding metasurface is below 10 dBsm in 6-16 GHz when the linearly polarized wave is incident vertically, a reduction of 20 dB compared to a metallic plane. Experimental tests were carried out on the samples using the free-space method and the experimental results were in agreement with the simulated results.

Secondly, a four-leaf rose-shaped reflective metasurface is designed, the reflection coefficient of which is greater than 0.96 in 8-14 GHz when the linearly polarized wave is incident vertically, and full transmission phase coverage in the 0-360° range is achieved by varying the rose leaf length. Genetic algorithm is used to encode and optimize the metasurface to achieve beam control in any direction. The results show that the genetic algorithm can effectively optimize the coding metasurface array. The radar scattering cross section values of the coding metasurface are -10 dBsm and -13 dBsm at 7.9 GHz and 10.1 GHz, respectively, with a reduction of 12.7 dB and 17.6 dB compared to the metallic plane. Experimental tests were carried out on the samples using the free-space method and the experimental results were consistent with the simulated results.

The results show that the metasurface designed in this paper can achieve beam control of linearly and circularly polarized waves and reduce the radar scattering cross section, which has certain application value in beam control and electromagnetic stealth.