A BROADBAND METAL-MESH HALF-WAVE PLATE FOR MILLIMETRE WAVE LINEAR POLARISATION ROTATION

Abstract

We present a polarisation rotator based on a dielectrically embedded metal Mesh Half Wave Plate (MHWP) working in the W- band frequency range (75{110GHz). The device was realised using metallic grids with sub-wavelength anisotropic geometries able to mimic the behaviour of natural birefringent materials. The device was designed using a combination of transmission line codes and flnite- element analysis able to achieve phase accuracy down to a fraction of degree. Very accurate intensity and phase measurements were carried out using coherent radiation from a Vector Network Analyser (VNA). The presented device performs better and it is much thinner than previous devices having reduced the number of grids by a factor two and minimised their inductive losses. The new mesh HWP has excellent performances in terms of difierential phase-shift ∞atness and cross-polarisation respectively 180:4 § 2:9 - and i28dB across a 25% bandwidth.