BANDWIDTH ENHANCEMENTS AND SIZE REDUCTION OF 3 DB PATCH COUPLER WITH 45° OUTPUT PHASE DIFFERENCE FOR 5G BEAMFORMING NETWORKS 10.5455/jjcit.71-1642931078 Nazleen S . M. Suhaimi,Anthony N . Uwaechia,Nor M. Mahyuddin 5G beamforming networks,Patch coupler,Output phase difference,Bandwidth enhancement,Size reduction 426 64 23-Jan.-2022 14-Mar.-2022 6-Apr.-2022 In this article, a single-layered 3 dB/45° coupler (Design D) is proposed for fifth-generation (5G) beamforming networks using cross-slotted patch topology, dumbbell-shaped slots, loaded stubs, notches and rectangular ground slots. The proposed Design D coupler is capable of eliminating the need for additional 45° phase shifters in the beamforming networks such as Butler matrix, which provides the main contribution in this work, especially in size reduction and bandwidth enhancements. The fractional bandwidths of 28.90%, 39.14% and 35.91% for -10 dB of |S11|, -3 dB ± 1 dB of |S31| and 5° phase imbalance of output phase difference are achieved by the proposed Design D coupler. The bandwidth enhancements of -3 dB ± 1 dB coupling coefficient, S31 and 45° ± 5° output phase difference for the proposed Design D coupler are 22.52% and 23.14% compared to Design A coupler, respectively. The bandwidth of 45° ± 5° output phase difference is increased by 16.3% owing to the presence of rectangular ground slots in Design D compared to Design C coupler. The patch size of the proposed Design D coupler is 0.22 λg x 0.23 λg. The electrical size of the proposed Design D coupler is reduced by 45.72% compared to Design A coupler.