“Metamaterial” refers to an artificial composite structure or a composite material with certain extraordinary physical properties that natural materials lack. Through sequential structure design of key physical dimensions of the material, limitations of certain apparent natural laws can be broken through, so as to obtain extraordinary material functions that go beyond inherent ordinary properties of the nature.
The refractive index profile inside the metamaterial is a key part for the metamaterial to demonstrate extraordinary functions. Different refractive index profile corresponds to different functions. With higher precision of the refractive index profile, the implemented functions are better. For conventional antennas, especially horn antennas, their aperture efficiency imposes great impact on improvement of antenna directivity and gain, and good far-field radiation responses are not available. In addition, dimensions of the antennas in the prior art are large and hardly reducible.