Cavity backed circularly polarized spiral antennas

Abstract

In this paper, a cavity backed spiral antenna is introduced. The antenna is a four-arm Archimedean spiral antenna. To effectively direct the radiation in the upper half space region, the spiral antenna is backed by a conducting cavity, which is peripherally filled by an absorber ring. Antenna radiates circularly polarized waves. The height of the surrounding cavity is only 7mm, which leads to an extremely low profile structure. The polarization purity and antenna gain are investigated over a wide frequency bandwidth of near 1 to 8GHz.