Wideband and metal‐only linear to circular polarization converter using multi‐slot elements

A wideband, metal‐only, and low‐cost transmission‐type polariser is proposed in which a plane wave with linear polarization impinging on the structure is converted to circular polarization wave on the other side and vice versa. The proposed structure is a quad‐layer frequency selective surface that its unit cell is composed of two sets of multi‐slot elements placed perpendicular to each other to achieve a wideband polariser. In this unit cell, by changing the length of the slots, the amplitude and phase of transmission coefficient can be controlled, which are used to create a 90‐degree phase difference between vertical and horizontal components of the incident electric field. A9 × 9 $9\times 9$ array of the proposed polariser with a quad‐layer is simulated and fabricated that shows the bandwidth of 22% (11.7–14.7 GHz) for an axial ratio below −3 dB and a transmission efficiency of more than 85%.