超材料吸波体具有传统吸波材料不具备的电磁特性，在军事与民用领域得到了广泛的应用。然而，传统的金属超材料吸波体存在吸收频带窄、不透明和耐久性差等问题。相比之下，利用液体和树脂材料设计的超材料吸波体可以弥补这些不足，但是以往的液体基超材料吸波体无法同时满足低频吸收和厚度薄的要求，因此，本文对具有低频吸收、超宽带、厚度薄和光学透明等优点的吸波体进行研究，主要研究内容如下：

首先，设计了一种花形结构的双向水基超材料吸波体。该吸波体在5.7-41.6 GHz内实现了90%以上的电磁吸收，其工作带宽覆盖了XC波段（5.85-8.20 GHz），相对带宽达到151.8%，具有良好的极化不敏感和入射角稳定特性。在TE极化下，斜入射角达到40°时，其吸收率保持在0.8以上；在TM极化下，斜入射角达到60°时，其吸收率保持在0.9以上。利用能量分布和等效电路对其吸收机理进行了分析。

其次，设计了一种乙醇基宽带透明超材料吸波体。通过材料选择、结构优化等步骤设计出了这种基于乙醇的超材料吸波体。该吸波体在1.82-40 GHz内实现了90%以上的电磁吸收，其工作带宽基本覆盖了LS波段（1.70-2.60 GHz），相对带宽达到182.6%，具有良好的极化不敏感和斜入射稳定性，在斜入射角达到50°（TE）和70°（TM）时，其吸收率均保持在0.8以上。并利用阻抗匹配理论、米氏谐振理论以及能量分布对其吸收机理进行了分析。

最后，利用深度学习设计了一种乙醇基宽带透明超材料吸波体。通过数据集生成、生成对抗网络训练、结构优化等步骤设计出了这种超材料吸波体。该吸波体在1.12-40 GHz内实现了90%以上的电磁吸收，其工作带宽覆盖了L波段（1.12-1.70 GHz），相对带宽达到189.1%，具有良好的极化不敏感和斜入射稳定性，在斜入射角达到50°（TE）和70°（TM）时，吸收率均保持在0.8以上。利用阻抗匹配理论和能量分布对其吸收机理进行了分析。

本文设计了三种宽带透明超材料吸波体实现了吸收带宽向低频的拓展并且保持着较薄的厚度，均通过3D打印技术制作样品并在微波暗室中进行了实验，实验结果与仿真结果吻合，验证了设计的正确性，为未来超材料吸波体的设计提供了参考价值和研究意义。

Metamaterial absorbers have electromagnetic properties that traditional absorbing materials do not possess, and have been widely used in military and civilian fields. However, traditional metallic metamaterial absorbers suffer from narrow absorption band, opacity, and poor durability. In contrast, metamaterial absorbers designed with liquid and resin materials can make up for these shortcomings, but the previous liquid-based metamaterial absorbers cannot meet the requirements of low-frequency absorption and thin thickness at the same time. Therefore, this paper studies metamaterial absorbers with the advantages of low-frequency absorption, ultra-broadband, thin thickness, and optical transparency. The main research contents are as follows:

Firstly, a bidirectional water-based metamaterial absorber with flower-shaped structure is designed. The absorber achieves more than 90% electromagnetic absorption in 5.7-41.6 GHz, and its working bandwidth covers XC band (5.85-8.20 GHz), with a relative bandwidth of 151.8%. It has good polarization insensitivity and stable incident angle. When the oblique incidence angle reaches 40°(TE), its absorption remains above 0.8; When the oblique incidence angle reaches 60°(TM), its absorption remains above 0.9. The absorption mechanism is analyzed using energy distribution and equivalent circuit analysis.

Secondly, an ethanol-based metamaterial absorber is designed. This metamaterial absorber based on ethanol is designed through the steps of material selection and structure optimization. The absorber achieves more than 90% electromagnetic absorption in 1.82-40 GHz, and its working bandwidth covers the LS band (1.70-2.60 GHz), with a relative bandwidth of 182.6%. It has good polarization insensitivity and oblique incidence stability, and its absorption remains above 0.8 when the oblique incidence angles reach 50°(TE) and 70°(TM). The absorption mechanism is analyzed by impedance matching theory, Mie resonance theory and energy distribution.

Thirdly, an ethanol-based metamaterial absorber is designed by using deep learning method. This metamaterial absorber is designed through the steps of generating data set, generating countermeasure network training and structural optimization. The absorber achieves more than 90% electromagnetic absorption in 1.12-40 GH, and its working bandwidth covers the L band (1.12-1.70 GHz), with a relative bandwidth of 189.1%. It has good polarization insensitivity and oblique incidence stability, and its absorption remains above 0.8 when the oblique incidence angles reach 50°(TE) and 70°(TM). The absorption mechanism is analyzed by impedance matching theory and energy distribution.

This paper presents the design of three broadband transparent metamaterial absorbers that achieve expanded absorption bandwidth towards lower frequencies while maintaining a thin thickness. The samples were fabricated using 3D printing technology and experimental measurements were conducted in an anechonic chamber. The experimental results are in good agreement with the simulation results, validating the correctness of the design and providing valuable reference and research significance for future metamaterial absorber designs.