Novel Design of Wideband Conjugate Feed for Compact Off-set Parabolic Reflector Antenna

The design of wideband conjugate feed with novel concept of post distribution along longitudinal direction is presented in this paper. These designs are attempted to reduce the cross-polarization in far field of off-set parabolic reflector with F/D of 0.4 and off-set angle of 90 degree. To generate TE 21 mode from TE 11 mode, the array of 5, 9 and 13 posts distributed longitudinally are used instead of single post. It has been observed that as number of posts are increases, the phase of TE 21 mode becomes frequency insensitive and giving rise to bandwidth. The radiation characteristics like co-polarization & cross-polarization and the relative phase & amplitude coefficient for TE 11 , TE 21 and TM 11 modes are optimized and presented. The bandwidth improvement of the order of 5.1% has been achieved with array of 13 posts as compared to 2.8% achieved by a conjugate feed with single post for 20 dB down cross-polarization.