基于相位突变的微波波段超薄透镜机理及应用研究

In this research, the ultra-thin lenses will be proposed and studied in microwave region based on the phase discontinurities, aiming at the limit of the thickness of tradioinal lenses, and the consequent weight and machining accuracy. The research will focus on the mechanism of the ultra-thin lenses, key factors affecting the performance of the lenses and the related applications. First, we will study the relationship between the abrupt phase changes of the sub-wavelength unit cells and the polarization of the incidence, incident angle, geometrical parameters of the unit cells and the rotation of the optical axis. Then we will propose the design method for sub-wavelength unit cells with desird responses of phase and amplitude. When the spatial phase distributions required by the generallized law of refraction are fulfilled, the ultra-thin lenses can be constructed. Second, in order to enhance the efficieny and the bandwidth of the ultra-thin lenses, the effective medium and equivalent circuit of the unit cells will be put forward, as the means to study the effects of the coupling between the unit cells and the impedance mathcing on the coupling efficieny of the crossed-polarized waves, and the complementary structure of the slot cells will be adopted to achieve the broadband effects. Third, we will design the ultra-thin lenses to achieve the focus of plane wave, the transform of cylidrical wave to plane wave and the three-dimensional anomalous refraction, respectively. Samples will be fabricated and measured to verify the theoretical design. Then we will develop the feeding network free microstrip antenna array. We believe that our result will reduce the thickness and the weight of microwave lenses significantly, which will enhance the integration of lenses with other components. This research will lay the foundation for the application of ultra-thin lense in communication system of the next generation.

针对微波透镜的厚度极限以及由其引发的重量、加工精度等问题，提出利用介质分界面上的相位突变替代电磁波在传播路径上的相位累积，构造微波波段超薄透镜，并从其工作机理、性能影响因素及应用三方面展开研究。首先，阐明亚波长人工电磁媒质单元的相位响应与入射波极化状态、入射角度、单元几何参数、光轴旋转等因素的内在关系，提出具有特定相位突变及幅度响应的亚波长单元设计方法，实现满足广义折射定律的离散化相位分布，构建微波波段超薄透镜；其次，建立亚波长单元所对应的等效媒质及等效电路，研究单元耦合及阻抗匹配对交叉极化波转化效率的影响，提高透镜效率并拓宽工作频带；第三，设计超薄透镜分别实现平面波聚焦、柱面波-平面波转换及三维异常折射，加工样品并进行测试，验证理论研究的正确性，并发展无馈电网络微带天线阵。本研究将在极大程度上减小微波透镜的厚度及重量，促进其与其他组件的集成化，为其在未来通信系统中的应用奠定基础。

本项目的研究主要针对微波透镜的厚度问题展开。在微波波段上，传统透镜的特定折射效应依赖于电磁波的透镜不同位置上传播距离的相位差，因此微波透镜存在无法逾越的厚度极限，并伴随由此引发的透镜重量、加工精度等问题。.在本项目研究中，提出利用超构表面的相位突变替代电磁波传播路径上的相位累积，针对微波波段上相位突变的激发机理、单层超构表面能量转化效率的理论极限值、宽带化、双层超构表面对能量转化效率的增强机理等基础理论问题展开研究，并以此为基础，提出了平面化异常折射透镜、非共面折射透镜、双极化透镜。进一步，本项目针对多种透镜样品进行了加工及测试，测试项目包括远场方向图、近场分布等。结果表明，实验结果均与理论结果及仿真结果相吻合，验证了理论研究的正确性。本项目从全新的角度提出了超薄透镜的设计方法，研究成果将拓展透镜功能，促进与其他组件的集成化，为其在通信系统中的应用奠定基础。