A broadband transition design between coplanar waveguide and air-filled substrate integrated waveguides for millimeter-wave applications

This work proposes a broadband transition between grounded coplanar waveguide to air-filled substrate integrated waveguide based on super-ellipse geometry for millimeter wave applications. Based on the order of the super-ellipse, two configurations are possible: a triangular and a semi-elliptical geometry. Back-to-back transitions in both configurations are designed to operate in K a -band. Both transitions offer a return loss better than 13 dB and an insertion loss less than 0.7 dB in the operating band. Further, the performance of the air-filled SIW is analyzed to quantify the attenuation constant, phase constant, and group delay. The loss due to each transition is computed using the post-processing data. The performance of the air-filled SIW is suitable to be used in millimeter-wave applications, and the proposed transitions also work well with the structure offering minimum insertion loss and good matching.