Ridge Gap Waveguide Wideband Hybrid Directional Coupler for Ka-Band Applications

The fifth generation (5G) is the next wireless mobile communication technology that targets to provide huge capac-ity, low latency and high data speeds. Like any new wireless technology, 5G requires the development of exciting techniques, where access to high frequency spectrum can achieve the desired characteristics. In addition, new systems must be developed and designed using wide bandwidth microwave components, which should be implemented with modern and efficient guiding structures. Among all the microwave components, directional coupler is essential device as it can be used to realize many subsystems such as beamforming networks. In order to keep up with the huge changes in future technologies, couplers still requires noticeable improvement, where wide bandwidth and low loss should be achieved throughout using modern guiding technology such as Ridge Gap Waveguide (RGW). In this paper, a design of ultra-wideband 3 dB quadrature hybrid directional coupler using RGW technology is introduced. The proposed coupler has a compact size of 1.58 λ×1.4λ and achieves a relative bandwidth of 44.7% at 33.5 GHz, which cover the whole ka-band. In addition, a stable 90° phase difference between the coupling and transmission coefficients is obtained over the whole frequency band.