Design of a microwave lens for 5G applications

Official URL: https://risc01.sabanciuniv.edu/record=b2767355_(Table of contents)

This thesis proposes a novel, low-cost, multilayer Rotman lens and antenna array for 5G applications at 28GHz band. The final design consists of a multilayered Rotman Lens, with the antenna array on the front and the Rotman Lens on the backside of the board. The lens and array are connected by slots opened to the common ground layer that is between them. This two layered structure made it possible to reduce the total footprint of the design. These slots were designed so that the insertion loss through them is less than 1dB. The design of the dummy ports found on the sides of the Rotman Lens was also changed. The dummy ports require 50Ω terminations to reduce the reflections occurring on the sidewalls to prevent unwanted phase shifts. The dummy ports were terminated using quarter wave transformation techniques. Using the quarter wave transformations, the dummy ports were matched to 200Ω. These transmission lines were paired in two so that they are each matched to 100Ω and require 100Ω terminations to These connections were done so that they act as terminations to each other. These connections made it possible to remove the 50Ω connectors necessary to reduce the sidewall reflections. This way, the size and cost of the design was lowered further. Conventional Rotman Lens designs can produce beams equal to the number of beam ports it has. The feeding network of the lens was designed using in-phase transmission lines, allowing multiple inputs to be fed together to generate two extra beams. The measured beams have gains between 9.2 and 13.7dBi. The beams cover an area of 80◦, with a 3dB bandwidth of 2GHz