Spiral antenna

A ( one-armed ) is comprised of a helical antenna in a plane spiral wound wire, wherein the radius of curvature and effective cross-section increasing from the inside to the outside. Helical antennas are among the logarithmic antenna and therefore are very broad band, that is, their properties are largely independent of frequency. Spiral antennas radiate circularly polarized.

A two-arm spiral antenna consists of two such conductors that are usually formed as a strip line. The feeding point is formed by the inner ends of the strip conductor. In contrast to helical antennas helical antennas radiate in both directions perpendicular to the spiral plane.

Mixed forms of spiral and helical antenna are conical or spherical cap, finished with twisted striplines body. These are like spiral antennas very broadband, radiation, however, directed in only one direction. They can be found, inter alia, due to its closed surface and the squat form on spacecraft telemetry.