Novel S and C Band TT and C Antennas for Satellite Applications

Abstract

Full spherical coverage from a single antenna cannot be provided at microwave frequencies on a normal satellite because of blockage by the satellite itself. However, cardioid coverage is sufficient. Achieving such coverage from a single antenna minimises the complexity of the on-board TT and C subsystem and so optimises both cost and reliability. Accordingly, investigations have been made into the feasibility of such an antenna in both S and C band versions. The design is a cylindrical waveguide, propagating a rotating TE mode, terminated in a circumferential array of axial slots and a short-circuiting plate into which an aperture is cut. A short metallic skirt can be added to the outside of the antenna if it is desired to reduce the coverage from the maximum achievable. The design has the advantage of being 'dual mode', i.e. it has two isolated Rf connectors providing identical pattern coverage. Thus two separate transponders can be 'hard-wired' on for reliability. The paper deals with the design, main development stages, an performance - including environmental testing results - of the antenna, and includes the results of investigations into a 'fill in' antenna intended to complete the spherical coverage if desired.