Quasi-octave bandwidth phase matched K/Ka antenna feed subsystem for dual RHCP/LHCP polarization

The architecture concept and fabrication of a quasi-octave bandwidth waveguide feed network for circular polarized antennas is discussed here. The main advantages of this extremely compact topology rely on three key achievements: the instantaneous bandwidth capability, the axial ratio improvement and the significant size reduction which is in many cases determinant in antenna feed subsystems. Experimental measurements exhibit very good agreement with the predicted results given by conventional mode matching techniques. The overall structure provides an axial ratio as low as 0.7 dB along with a return loss better than 25 dB, at every waveguide port, over the whole bandwidth (60%), which represents the today's state-of-the-art. Moreover, yield analysis and simple scaling properties assure the use up to Q band.