Four-Armed Spiral-Helix Antenna

An antenna formed by the union of a four-armed, reflective-backed spiral antenna with a top-fed quadrifilar helix, operating over the 0.35-2.6-GHz band, is presented. The antenna features a novel dual-layering scheme that allows the modal impedance of the four-armed spiral to be greatly reduced while maintaining the desirable self-complementary metallization. A reconfigurable end-loading scheme is also presented that allows the attachment of high power-handling resistive loads, which along with other design features enables the use of the antenna in high-power transmitting applications. Mode 1 VSWR less than 2.2 is maintained throughout the 0.35-2.6-GHz band. Respective cutoff and nominal gains of 0 and 7 dBiC with excellent pattern characteristics are demonstrated. Over 30 dB broadside cross-polarization discrimination and high conical pattern uniformity are also obtained.