Reconfigurable square ring antenna for switchable circular polarisation

A reconfigurable ring antenna for switchable circular polarisation (CP) is presented. The proposed antenna consists of a square ring resonator with two gaps, two pin diodes and a square ring slot with a link on the ground plane. Depending on the location of the gap (link), the square ring (slot) resonator exhibits different directions of linear polarisation. By selecting a suitable gap/link position, two orthogonal resonant modes are excited, and good CP is achieved. The pin diodes are positioned in the middle of the gap. The state of the gaps can be adjusted by pin diodes´ state. As a result, the proposed antenna can radiate with either right-hand CP or left-hand CP.