Reflective switchable polarisation rotator based on metasurface with PIN diodes

A planar metasurface that rotates the polarisation of reflected signals by 90° is presented in this article. The surface also permits the relative phase of the rotated, reflected signal to be controlled. The metasurface rotator uses a square printed patch element mounted above a conducting ground plane. The addition of PIN diode controlled VIAs (Vertical Interconnect Access) at the corners of each square patch provide the ability to modify the scattering properties of the surface. In particular, the surface can be programmed to shift the phase of the rotated waveform by +/-90°. The polarisation rotator was manufactured, measured and compared against numerical simulations and the maximum measured bandwidth was 25% (4.8-6.2 GHz) for co-polarised attenuation of 10 dB. The proposed surface can be adopted for practical applications such as circularly polarised antennas.