A low sidelobes helix radiator for an high power tracking antenna system

A tapered helix was analyzed and constructed to obtain a low-sidelobe axial mode radiation characteristic. On the basis of the theoretical current distribution, the behavior of the tapered helix radiation pattern was evaluated in order to find a region of low sidelobe radiation. A high-power low-sidelobe antenna was built. The measured radiation pattern shows fair agreement with the theoretical predictions. The helix is used as part of a high-power tracking antenna system. The study demonstrates that a conical helix can be designed to have a relatively narrow 3-dB beamwidth while maintaining low-sidelobe radiation for a narrow bandwidth only, wide-bandwidth low-sidelobe radiation can be obtained only for low-gain conical spirals, and small pitch angles reduce sidelobe level for constant cone angles.<>