Backfire/Endfire conical beam properties of conical spiral antennas with arbitrary configurations
A four-arm conical spiral antenna with arbitrary configuration and excited by different modes is analyzed by the method of moments. Both Archimedean and equiangular spiral antennas are unified in its coordinate equation. The results show that backfire and endure shaped-conical beams can be obtained by different exciting types. The relationship between its radiation characteristics and winding denseness as well as its feeding modes is discussed. With the increase of the winding denseness the beam deviation from the axis augments while its beam conformity deteriorates. To get the best radiation performance, an octo-filar spiral antenna that can generate backfire radiation patterns is proposed.