Design of broadband planar substrate integrated waveguide (SIW) transvar coupler

In this paper, a design of broadband planar substrate integrated waveguide (SIW) transvar coupler is demonstrated. A study has been carried out to explore the effects of the number and size of coupling apertures, placed in the side wall of the four port coupler, on its performance. A design curve is also formulated to relate the bandwidth performance of the coupler with the number of apertures. Finally a six aperture coupler has been designed and fabricated to validate the simulation results. The proposed coupler is a good candidate for circular polarized antenna feeding network.