Theory and Design of 20/30 GHZ Band TM01/HE21 Mode Tracking Coupler

The paper presents the design and testing of 20/30 GHZ band tracking coupler. It will be integrated to a tracking four ports, linear polarized feed system. The tracking modes TM01 and HE21 are coupled, by means of Tchebitchef coupling holes, in secondary waveguides having the same phase velocities. An improvement of the isolation value in the transmit band is achieved by corrugating the coupling rectangular waveguides. A simple formulation gives the relation between the resonance frequencies, due to the presence of the holes, and the corrugated circular guide dimensions. Experimental performances for a design coupler are also given.