Metallic Monopole Parasitic Antenna with Circularly Polarized Conical Patterns

In this paper, a new geometry for antenna producing conical patterns with circular polarization is proposed. The symmetrically placed parasitic posts, with different horizontal and vertical segments, around the centrally fed monopole control the circular polarization purity and the angle of maximum gain. The 3-D geometry favors high gain at low elevation angles. A circular ground plane atop a choke ring facilitates easy mounting of a radome and improves gain at lower elevation due to lower backlobe. The all-metal radiator has good mechanical stability and remains impervious to large temperature variations, which is ideal for use in space applications. An application to a Martian transponder at the $X$ -band is also discussed. The measured results of the manufactured antennas show a good agreement with those of the simulated one. Furthermore, the optimization of the antenna design parameters allows the antenna to have high gain and low axial ratio (AR), from high elevation ( $\theta _{max}=35^{\circ }$ ) to low elevation ( $\theta _{max}=70^{\circ }$ ) angles.