Research On The Beam Scanning Antenna Array Based On Gradient-index Device

Beam scanning array can achieve high gain radiation and flexible beam scanning. However, its applications are limited by some challenges, including the confined scan angle and the high complexity of array architecture. Gradient index (GRIN) devices can be used to control the propagation of electromagnetic wave. Beam scanning systems realized by means of GRIN devices processes attractive advantages, such as high directivity, large scan angle and low loss. Meanwhile, the development of transformation optics (TO) and metamaterial provided effective theory and realization methods to design novel GRIN devices. Realization of beam scanning with GRIN devices has attracted much research attention.Firstly, a novel beam scanning array architecture based on Luneburg lens is proposed. Since Luneburg lens can focus incident plane wave at a certain point on its spherical surface, discrete radiation elements are mounted on the spherical surface of a Luneburg lens and fed alternatively to generate high-gain and wide-angle scanned beams. In addition, the configuration of Luneburg lens fed by a linear array is proposed. By controlling the array excitation, its phase center can be shifted and consequently the radiation beam of the Luneburg lens scan continuously. To demonstrate the above design, feed networks with desired excitation distributions are designed and connected to a 4-element monopole feeding array to achieve several scan angles with similarly high gain.Secondly, the planar feeding elements capacity of the conventional flattened Luneburg lens is analyzed, which indicate the focal plane size of conventional flattened Luneburg lens is insufficient to accommodate enough feeding elements for half-power-beam width (HPBW)-covered electronic scan. Then, a novel extend-flattened Luneburg lens is proposed based on quasi-conformal transformation optics (QCTO) method, whose focal plane is enlarged to accommodate enough elements to ensure scanning beam HPBW-covered. As a verification of the design, a novel extend-flattened Luneburg lens prototype composed of periodic dielectric structures is manufactured using 3D printing techniques. This prototype is fed by a 9-element planar microstrip antenna array on its focal plane. The experimental results demonstrate ±42° HPBW-covered scanning capability with different antenna elements being fed.Finally, based on the birefringence principles, a non-magnetic birefringent GRIN lens is proposed, which is composed of periodic dielectric structures. The required anisotropic permittivity distributions of different birefringent GRIN devices have been analyzed. A novel birefringent radial-GRIN dielectric lens has been studied, which integrate the functions of both Luneburg lens and Eaton lens. It can focus the horizontal-polarized incident plane wave on its surface and deflect the vertical-polarized wave with a certain angle. A birefringent lens prototype of this kind whose deflection angle is 30° for the horizontal-polarized wave is designed and manufactured based on periodic dielectric structures. Its focusing and deflection functions are verified.