紧凑型人工电磁媒质设计及其在天线中的应用

Since most prevously reported artificial electromagnetic (EM) material(also named metamaterial (MTM)） cells feature relatively large dimensions, the mutual coupling between neighboring cells is strong and thus large deviations between numerical simulations of the designed devices and antennas under the effective medium theory and measurements are suffered. This project proposes a set of novel more compact MTM cells based on the study of fractal-pertubed composite right/left handed transmission lines and the framework of the effective medium theory. (1) First, the equivalent circuit model is proposed, then the transmission line theory analysis is performed and the effective parameters analysis is conducted. A generic design approach and theory of the compact artificial MTM cells are derived by investigating the relation among the resonant current distribution, effective medium parameters and circuit parameters. (2) Second, various artificial MTMs made of compact cells are put forward on the basis of the proposed approach and theory. The unique EM characteristics such as weak mutual coupling, broadband and multiband are comprehensively studied. (3) Finally, the design and application of these compact artificial MTMs to novel antennas are extensively explored, such as miniaturized MIMO system antennas with weak coupling, miniaturized broadband or multiband antennas, and high-directivity antennas, etc. This project is expected to advance a step for homogenized MTMs and achieve a breakthrough, and the research achievements will enrich the effective medium theory and improve the success rate of the first design. Moreover, the research will facilitate the real applications of the artificial MTMs and implementation of the compact antennas with super performances, thus it has a comprehensive scientific meanings and considerable engineering values.

以往电磁结构单元尺寸较大，单元间互耦强，以致基于等效媒质理论设计的器件和天线性能与实际有偏差。本项目在分形复合左右手传输线研究的基础上和等效媒质理论框架下研究一类具有单元结构更加紧凑的新型人工电磁异向介质。首先建立其等效电路并进行理论分析和等效媒质参数分析，通过研究谐振电流分布与等效电磁参数和电路参数的关系，建立紧凑型人工电磁媒质单元结构设计的一般理论和方法；其次基于该理论和方法提出多种具有紧凑单元结构的人工电磁媒质并全面分析其独特的电磁特性（如低单元间耦合，宽频，多频特性等）；最后探索紧凑型人工电磁媒质在新型天线中的设计和应用问题，如低耦合小型化MIMO系统天线，小型化宽频，多频天线以及高方向性天线等。本项目可望向均一化媒质迈进并实现突破，其研究成果将丰富有效媒质理论，提高一次性设计的成功率，有望加速人工电磁媒质的应用步伐和小型化高性能天线研制，具有广泛的科学意义和可观的工程应用价值

人工电磁媒质具有很多新颖的电磁特性，能够实现超强的电磁波调控，引发了新型微波器件和天线的研制。本项目围绕紧凑型人工电磁媒质设计与天线应用这一主题，系统建立了小型化、多/宽频、单负、高极化纯度人工电磁媒质单元的优化设计理论、一般设计方法和准则，并研制了多种紧凑型人工电磁媒质单元。在高性能天线制备方面，通过独立自由调控结构的介电常数和磁导率参数，首次提出了基于波导磁电媒质的微带天线带宽展宽原理，构建了基于分形结构、八分之一模基片集成波导、电磁超表面等设计了多频贴片天线、多频漏波天线、多频透镜天线等的设计方法，并研制了多种多/宽频天线；率先建立了基于波导电负媒质的阵列天线高效解耦新方案，设计了多种单负电磁媒质单元，显著降低了天线阵元间耦合，有效解决了天线电磁兼容难题；利用基片集成波导结构的极化独立特性提出了高极化纯度漏波天线的设计方法，并基于极化滤波电磁媒质单元建立了高极化纯度透镜天线的制备方案，研制的新型漏波天线和透镜天线具有很高的极化纯度；系统研究了基于紧凑型复合左右手传输线结构、电谐振单元、磁谐振单元以及电磁谐振复合单元的天线小型化工作机制，研制了多种小型化天线，建立了完整的小型化天线设计方法；提出了基于三维分形零折射率和渐变折射率媒质的高方向性天线设计方案，首次同时提高了喇叭天线E和H面的方向性，基于多层耦合单元研制了线极化/圆极化透镜天线系统，形成了一套电磁媒质在高方向性天线中的应用范例；建立了基于分形渐变折射率单元的波束可调透镜天线设计方法，实现了天线系统的波束数量和方向性的自由调控，基于新型慢波传输线（SW-TL）设计了紧凑型Butler矩阵并研制了多波束天线系统，实现了良好的波束扫描功能。本项目基于人工电磁媒质理论和新型物理机制，极大的缩短了天线系统的研发周期，为我国发展高性能天线提供了坚实的理论支撑和崭新的技术途径。