Research And Application Of Metamaterial Luneburg Lens

Luneburg lens is a spherical lens with continuous gradient of refractive index.Any point on the lens surface can be used as its focus.Its measurement accuracy is high and its bandwidth is very wide.Luneburg lens antenna can enhance the ability to receive reflected signals.The spherical design can make it transmit beams in all directions of the whole space,have a field of view without blind angle,and realize multi-beam scanning without moving the feed antenna.Luneburg lens has good beam focusing ability and multi-beam characteristics,so it has good research prospects.However,due to the manufacturing technology,Luneburg lens is still not popularized on a large scale.The new metamaterial has the advantages of small size,light weight and easy manufacture.The Luneburg lens can be constructed by using metamaterial units to solve the manufacturing problems.This thesis focuses on the key technology of Luneburg lens design and its application in multi-beam scanning.The main contents include:(1)A spherical Luneburg lens antenna array with ultra wide angle scanning is designed.Firstly,the refractive index of Lomber lens is discretized and simplified according to the concept of "pixel dot ",and then a "cross" small unit is designed to equivalent the discretized refractive index,which can be manufactured by 3D printing technology.A 26 beam microstrip circularly polarized antenna array is designed for the 3D printed spherical lens.At the center frequency of 28 GHz,its realized gain is 21.95 d Bi,which is more than 14 d Bi higher than that of the circularly polarized antenna without lens,and the beam scanning in the upper half space is realized.(2)A circularly polarized Luneburg lens based on transform optics is designed.Using the method of coordinate transformation,the spherical lens is compressed into a cylindrical lens,and then it is discretized into a "cross" small unit,which is manufactured by 3D printing technology.The cylindrical lens not only has the same function as the spherical lens,but also reduces the volume and weight of the Luneburg lens,and the feed can be placed parallel to the bottom of the cylindrical lens,which solves the problem of inconvenient lens and antenna integration.(3)A broadband two-dimensional Luneburg lens antenna array is designed.A novel metasurface structure of split-ring resonator is proposed,and the radial gradient refractive index distribution is realized by changing its element size.For the two-dimensional lens,a broadband planar Luneburg lens antenna array with log periodic dipole as feed is designed.When the frequency is 14.77 GHz – 21.16 GHz,the wide-angle beam scanning on the horizontal plane is 193.11 ° through the switching antenna in the array.