Contra-Directional 3dB 90° Hybrid Coupler in Ridge Waveguides Using Even and Odd TE Modes
A novel compact wide-band contra-directional single conductor ridge waveguide coupler is presented. It exhibits 50% fractional bandwidth with equal power split between the through and coupled ports while occupying a very compact volume. The design can be exploited in versatile applications, such as beam forming, or high-power combiners. The methodology to design the coupler is presented. It starts with designing the coupling section in a modified double ridge waveguide that supports two independent propagating TE modes. Proper choice of the cross section allows the designer to achieve the required impedance levels for tight coupling values, not common for standard waveguide contra-directional couplers. An S-band proof of concept prototype was synthesized, simulated, fabricated and tested demonstrating excellent measured results without any tuning.