Generation of Circularly Polarized Conical Beam Pattern Using Torus Knot Antenna

A wideband circularly polarized antenna with a conical beam radiation pattern is presented. It consists of a torus knot as a radiator and a feeding probe to excite it. The proposed feeding mechanism is simple and does not use power divider network to generate circular polarization (CP). Characteristic mode analysis of a knot shows that a particular kind of knot, with a suitable excitation, can radiate omnidirectional beam with CP. To validate the design, a prototype of torus knot antenna is realized using additive manufacturing technology. The return loss, radiation pattern, and axial ratio (AR) are measured. A parametric study is carried out to understand the effect of various geometric parameters on the performance of the antenna. The fabricated torus knot antenna has a usable bandwidth of 51.8% and the measured AR bandwidth is 66%.