Design and analysis of a circularly polarized Nabla-slotted waveguide antenna for reflector application

Abstract A novel compact Ku-band waveguide antenna is proposed that offers left-hand circular polarization (LHCP). The proposed design has Nabla slot on aperture of circular waveguide to attain LHCP. Side fed design of the proposed antenna eliminates the need for rectangular to circular waveguide transition. The antenna has the reflection coefficient ( S 11 ) below −10 dB from 12 to 15.2 GHz, corresponds to the impedance bandwidth of 23.5% and axial ratio (AR) below 3 dB from 13.2 to 15.2 GHz, attained circular polarization bandwidth as 14%. Measurement results indicate that the proposed antenna achieves a 12 dB half beamwidth of around 65° across the 13.4–15.2 GHz frequency band, resulting in an attained pattern bandwidth (stable radiation pattern range) of 12.5%. This performance fulfills the illumination requirements for an offset parabolic reflector with an f / R D ratio of 0.25.