Fast prototyping of an 8×8 butler matrix beamforming network for 5G applications

The era of 5G is going to dominate mobile network applications sooner or later, supporting the higher data rate communication. There is a fundamental aspect enabling the faster mobile communication: millimeter wave phased array antenna. This requires much higher frequencies and more complicated system designs over the current 4G LTE system. In this paper, we use the frequency-domain transmission line equation in COMSOL Multiphysics to quickly design and simulate an 8×8 Butler matrix at 30GHz that can be fabricated on a single layer without using any air-bridges or metalized vias. It is a cost-effective passive Beam Forming Network (BFN) for phased array antennas since the circuit can be fabricated in the form of microstrip lines and it is feasible to perform beam scanning without using expensive active devices in a 5G system. The simulation results show the ideal arithmetic phase progression at each output port of BFN and the radiation patterns generated by an 8×1 patch antenna array connected to the feeding network when each input port is excited. The main lobe is steered from one side to the other side along the output ports due to 112.5° arithmetic phase progression that is controlled by the BFN excitation port.