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.