Dual Polarized Geodesic Lens

Sammanfattning: Gradient-index (GRIN) lens antennas, such as the Luneburg lens, posses attractive electromagnetic properties. The smooth change in refractive index ensures no internal reflections and the focusing of the electromagnetic waves results in a directive antenna. The main challenge of the design of a GRIN lens is acquiring the required refractive index. Two dimensional dielectric lenses can be realized using 3 dimensional homogeneous surfaces eliminating the challenge of discritizating the continuous change in refractive index. These type of lenses are commonly referred to as geodesic lenses. In this thesis a dual polarized geodesic lens antenna is presented. The antenna consists of two metal plates that form a parallel plate waveguide (PPW) section which is deformed to mimic the behaviour of a Luneburg lens. The antenna operates in the Ka band and polarizer unit cells are employed to alter the polarization state of the antenna. The polarizers are placed in a circular configuration in the flare of the antenna to maintain a compact design and good scanning range. Eleven waveguide feeds are used with 10° separation resulting in a scanning range of ±50° in the azimuth plane. The final design is a lens antenna with a center frequency of 28 GHz and 20 % bandwidth. Simulations of the design show reflection coefficients below -15 dB and crosstalk below -17 dB. The total efficiency at 28 GHz is 90 % and above 85 % for the full frequency band.