A metasurface‐based broadband reflective polarisation converter with dual L‐shaped patches and dual trapezoidal patches for linear‐to‐linear polarisation conversion and linear‐to‐circular polarisation conversion is proposed in this study. The simulated and measured results demonstrate that the polarisation rotation can be effectively implemented in the frequency bands 9.24–12.25 GHz and 21.23–23.01 GHz, with the fractional bandwidth of the former being 28.01%. In addition, linear‐to‐circular polarisation conversion is performed with fractional bandwidths of 42.86% and 14.49% at 13.09–20.23 GHz and 23.62–27.31 GHz respectively. In the primary bands of linear‐to‐linear polarisation conversion and linear‐to‐circular polarisation conversion, the converter can operate within an incident angle range of 55° for polarised wave. This design may have potential uses in polarisation control devices used in the field of communications in X‐, Ku‐ and K‐bands.

In this work, a transmission polarizer is described by using a frequency-selective surface to transform linearly polarized waves into circularly polarized waves. The linear to circular (LTC) polarizer consists of four layers. Two types of unit cells are designed in the LTC polarizer to improve design freedom. As a result, two orthogonal polarized components of transmission waves display nearly 90° phase differences while maintaining nearly high transparency for the generation of CPWs. The less than 3 dB axial ratio with a fractional width of over 76.8% from 9.20 to 20.67 GHz for this LTC polarizer is obtained. Even when the incident angle reaches 20°, its operating frequency band covers 9.69 to 20.21 GHz. Compared with the converters proposed before, the one proposed in this paper has a wider bandwidth. In order to evaluate the design strategy, a prototype is manufactured and tested. The results of the simulation and the experiment are in good accord.