A Circular Polarized Feed Horn With Inbuilt Polarizer for Offset Reflector Antenna for $W$ -Band CubeSat Applications

A novel <inline-formula> <tex-math notation="LaTeX">$W$ </tex-math></inline-formula>-band left-hand circular polarized (LHCP) cylindrical waveguide feed horn antenna is proposed. The proposed antenna features an inbuilt polarizer structure and a single side-fed linear polarized input to offer symmetric LHCP radiation pattern. The internal polarizer structure consists of nine pairs of circular cavities to generate a circularly polarized wave, eliminating the need for an orthomode transducer or a complex septum. The side-fed horn reduces the overall length by eliminating the rectangular to circular waveguide transition. The proposed horn antenna’s electrical dimension is <inline-formula> <tex-math notation="LaTeX">$7.2\lambda \times 3.9\lambda \times 1.4\lambda $ </tex-math></inline-formula> at 84 GHz. The antenna has impedance matching (<inline-formula> <tex-math notation="LaTeX">$S_{11}$ </tex-math></inline-formula> below −15 dB) and axial ratio below 1.2 dB from 79.5 to 88 GHz. The horn is used as a feed source for an offset parabolic reflector of 10 cm diameter and small <inline-formula> <tex-math notation="LaTeX">$f/D$ </tex-math></inline-formula> ratio 0.25, which can fit inside a CubeSat. The reflector antenna provides the simulated right-hand circular polarization (RHCP) directivity of 36.6 dBic at 86 GHz with spillover loss of 0.83 dB. The feed reflector assembly is also simulated with the complete aluminum CubeSat chassis. The measurement of the prototyped feed horn and the offset parabolic reflector antenna validates the analysis and simulation results.