Computer-aided design of octo-filar helix antennas with fixed arm length

An octo-filar helix antenna that can form a backfire or endfire conical beam by changing its pitch angle and feeding modes with its arm length invariable is researched by the Nakano integral equation and the method of moments. A shaped-conical radiation pattern with good circular polarization performance and the best beam conformity can be obtained for almost all the hemisphere. Comparison of the radiation properties, including the beam direction, maximum power gain and 3-dB axial ratio angle coverage under different feeding modes is conducted. The relationship between the pitch angle and the height of the satellite orbit is also presented, which provides theoretical references for the design of the antenna.