超构天线:原理、器件与应用

自从电磁波被发现和应用以来,利用各种材料或者结构调节电磁波的辐射行为、构造高性能的电磁辐射器件一直是研究人员的追求目标.经过百余年的发展,电磁辐射器件的方向性提高、带宽拓展等技术逐渐达到瓶颈.受自然材料电磁特性的限制,微带天线、喇叭天线等传统电磁辐射器件存在体积重量大、工作带宽窄、无法快速动态调控等缺陷,难以满足日益发展的通信技术的需求.近年来出现的亚波长结构可在深度亚波长尺度下调控电磁波的传输行为,出现了多种奇异的电磁现象,完善了传统的电磁学理论,在一定程度上突破了传统材料电磁特性的限制,形成全新的电磁辐射技术,有效解决了传统天线存在的口径大、厚度高、带宽窄等难题,促进了电磁学、光子学、材料学等领域的发展.这种基于超构材料的新型天线可以被称为超构天线,具有高方向性、低副瓣、超宽带、可重构等传统天线难以实现的功能.本文主要回顾了近年来基于亚波长超构材料的超构天线技术的发展现状和取得的成果,介绍了超构材料在亚波长尺度下对电磁波振幅、相位、偏振态等的衍射调控机理,以及在此基础上形成的新型辐射器件,例如相控阵天线、高方向性天线、低雷达散射截面天线,基于亚波长结构的多种偏振调控器件及其在天线中的应用等.在衍射极限尺度下,这种亚波长结构的调控行为可有效提升电磁辐射器件的方向性、带宽,并可重构天线的工作频率、偏振态等性能.

Meta-antenna: principle,device and application

Since electromagnetic waves were discovered, effectively controlling them has been a goal and radiators with better characteristics have always been chased by researchers. However, limited by the electromagnetic properties of nature materials, traditional radiation technology is reaching its bottleneck. For example, traditional microwave antenna has the disadvantages of large volume, heavy weight, narrow operating frequency band, etc., and cannot satisfy the development requirement of modern communication systems. Therefore, the state-of-art radiation technology meets the challenge of minimizing the size and broadening the bandwidth of radiators, and constructingmulti-functional and reconfigurable antennas. In recent years, metamaterials have aroused great interest due to the extraordinary diffraction manipulation on a subwavelength scale. Fruitful bizarre electromagnetic phenomena, such as negative refraction index, planar optics, perfect lens, etc. have been observed in metamaterials, and the corresponding theories improve the fundamental principle systems of electromagnetics. Based on these novel theories, a series of new radiators has been proposed, which has effectively overcome the difficulties in traditional radiation technology and broken through the limits of natural electromagnetic materials. The relating theory and technology may greatly promote the development of electromagnetics, optics, materials. In this article, we mainly review the recent progress in the novel electromagnetic radiation technology based on metamaterials, which is named meta-antenna, including the principle of diffraction manipulation of metamaterial to control the amplitude, phase and polarization of the incident electromagnetic waves. Subsequently, a series of radiation devices is introduced, including the new phased array antenna on the concept of phase manipulating metamaterial, and the high directivity antenna based on zero refraction index metamaterial and photonic crystal, and the low RCS antenna simultaneously has the functions of gain enhancement and stealth ability. Besides, the polarization manipulation characteristics of metamaterial are also reviewed. The anisotropic and chiral metamaterials are analyzed, and several polarizers with broadband characteristics and reconfigurable ability are introduced. Furthermore, due to the importance as future radiation sources, nanolasers that work on a subwavelengh scale are demonstrated. Finally, we point out the current problems and future trend of the radiation technology based on metamaterials.