A study on conical spiral antennas for UHF SATCOM terminals

A spiral antenna can be designed to cover the octave bandwidth of 200-400 MHz required for the UHF SATCOM system. To make it easily stowed and deployed on demand, the spiral can be printed on a collapsible conical surface similar to a center-fed-reflector deploying mechanism. This paper studies two different configurations for the conical spiral antenna with different subtended conical angles. The first configuration assumes constant radius for the projected circular aperture with different conical angles, requiring different conical length or height. The second configuration assumes same conical length for different conical angles, resulting in different projected circular apertures. The study provides a trade-off between antenna gain, back lobe level, axial ratio, and stowed size.