Beamforming Network in Square Waveguide Technology for 5G Communications

This paper presents the design of a compact Rotman lens using square waveguide (SWG) technology for operation in the Ka band. The design is achieved by calculating the effective behavior of the waveguides that comprise the ports, the central cavity, and the transitions between the ports and the central cavities. In order to validate the operation of the Rotman lens at the array ports, cross-slot antennas were incorporated into the design. A seven-beam port feeds a nine-element array with eight dummy ports, which serves to reduce the occurrence of secondary lobes above -12.0 dB and to enhance the lens geometry. The designed lens was subjected to simulation and validation using a number of tools, including the CST Microwave Studio with the frequency solver. The simulation results demonstrate that the lens is capable of functioning in both the TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</inf> and TE<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">01</inf>, thus doubling its capacity. The transmission coefficient reaches a level of 9.5 dB within the frequency range of 28.0 to 33.0 GHz, with an available bandwidth of 16.4%. The return loss level is 13.5 dB when both modes are considered. Furthermore, a cross-slot design is presented for incorporation into a future prototype, which will be constructed using a numerical control machine or a 3D printer to facilitate the subsequent metalization process for experimental measurement.