Plannar Spiral Antennas Applied on Short-Wave Communications

When dual-arm planar spiral antenna is fed by the amplitude of a reverse-phase electric current, the right circular polarization is happened along the direction perpendicular to the plane of the antenna and the radiation lobe of the antenna is near vertical incidence. Dual-arm planar spiral antenna is designed and suitable for short-wave communications, especially in communications blackout of the ranges within 0-200 km, due to its characteristics of near vertical incidence sky-wave (NVIS). Short-wave communication can be implemented on the range of 0-200 km in a very wide frequency band without any interruption, when graded lines are used in the antenna for impedance match.