Development of short backfire antenna fed by H-shaped excitation structures

Cross aperture patch excitation structure of short backfire antenna blocks radiations between primary reflector and sub-reflector and provides non reconfigurable circular polarization (CP) characteristics. H-shaped cross dipole excitation structure for short backfire antenna is presented in this paper. The cross dipole consists of two orthogonal H-shaped dipoles. This excitation structure reduces blockage of radiations between sub-reflector and primary reflector and provides reconfigurable circular polarization characteristics. H-shaped cross dipole is mounted on the outer conductor of the slotted coaxial line. Based on this excitation structure, different other excitation structures are developed to get elliptical, linear polarizations, and dual impedance bandwidth characteristics of the antenna. The antenna is developed on elliptical ground plane with inexpensive dielectric and metallic rims. It is demonstrated that H-shaped cross dipole excited short backfire antenna can achieve voltage standing wave ratio bandwidth of 21.28% for 2:1 VSWR, axial ratio of 0.82 dB with axial ratio (≤ 3dB) bandwidth of 2.34% and a gain of 12 dBi. The simulation and experimental results are presented and discussed.