Frequency selective surface as a polarisation transformer

The polarisation transformation properties of frequency selective surfaces are reported. Examples of microstrip structures which transform polarisation from linear to circular are described. A relatively broadband polarisation transformer can be designed for a limited range of angles of incidence. Alternatively, a polariser for a wide range of angles of incidence can be designed to operate over a narrow frequency band. A polariser that can be electronically switched is also characterised. The finite-difference time-domain (FDTD) method and the waveguide simulator technique are used to analyse the reflection of a plane wave from these periodic structures.