Miniaturized Rotman lens with applications to wireless communication

Rotman lens is a type of beamforming network with many advantages, such as true-time delay characteristic, multibeam capability, and wide bandwidth. Rotman lens has been used in a wide range of applications in today’s wireless communication systems. However, the size of a conventional Rotman lens is considerably large. So, difficulties may arise with respect to its integration with base station antennas in wireless communication systems. In this study, three techniques for the miniaturization of a Rotman lens, i.e., Chebyshev impedance transformers, power dividers, and truncated ports with energy distribution slots, are introduced to design the Rotman lens to reduce the size of the ports and hence the total area occupied by the Rotman lens. Simulation and measurement results indicate that good impedance matching between the lens body and its feed lines can be achieved. Using the proposed truncated ports with energy distribution slots, the size of the Rotman lens can be greatly reduced without performance degradation or production cost increment. Moreover, two possible applications of the proposed miniaturized Rotman lens to wireless communication systems are investigated. Rotman lens can not only provide multiple phase difference signals along the array ports to realize multibeams, but also generate high-performance formed beams such as flat-topped radiation pattern.