Dual-frequency circularly polarized antennas based on stacked monofilar square spirals

Two radiating spirals stacked on a foam substrate are used in the design of a circularly polarized antenna designed to respect new bandwidth constraints resulting from the emergence of multimedia services in satellite communications. Orthogonal circular polarizations are required for up and down links over large frequency bandwidths. In the single antenna, 4 to 5% axial ratio (AR) bandwidths are observed in a large beamwidth for both bands. This AR bandwidth increases appreciably (24 to 31%) when two antennas are combined in a sequentially rotated configuration.