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 to eliminate 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 guided wavelength x 0.23 guided wavelength. The electrical size of the proposed Design D coupler is reduced by 45.72% compared to Design A coupler.
Key words: 5G beamforming networks, patch coupler, output phase difference, bandwidth enhancement, size reduction.
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