A 3-12GHz compact broadband circularly polarized Archimedean planar spiral antenna

A compact broadband circularly polarized Archimedean planar spiral antenna is proposed. The proposed antenna is consisted of a two-armed Archimedean spiral antenna. The current path is elongated by sinusoidal loading of Archimedes lines to miniaturize the size of proposed antenna. Two 100 Ω lumped resistors are loaded to improve the radiation performance of antenna in low frequency. Forward radiation and improved axial ratio performance are achieved through loading a metal back cavity with two orthogonal rectangular slots and a circular slot at the intersection of the rectangular slots at the bottom of antenna. The size of the proposed antenna is 44 × 44 × 30 mm
³
. The proposed antenna achieves a voltage standing wave ratio (VSWR) of less than 1.5, an axial ratio performance of less than 3 dB, and a gain performance of more than 4 dBi in the range of 3-12 GHz.