A Polarization-Rotating SIW Reflective Surface With Two Sharp Band Edges

A single-layer polarization-rotating reflective surface with two sharp band edges is proposed in this letter using the substrate integrated waveguide (SIW) technology. The linearly polarized incident electromagnetic wave can be reflected back with its polarization rotated orthogonally, and two sharp band edges of the cross-polarized reflection coefficient can be achieved using the proposed reflective surface. The periodic element of the proposed reflective surface is a square SIW cavity resonator with two parallel L-shaped slots etched on its front side. The operating principle is investigated with the mode analysis and parametric study performed. A more accurate analysis on the structure with one L-shaped slot is presented. Moreover, the leaky mode and coplanar waveguide (CPW) mode of parallel slots are introduced to explain the operating principle of the modified structure with two parallel L-shaped slots. A prototype is designed and fabricated with its frequency centered at 34.5 GHz to validate the proposed structure. The simulated and experimental results are consistent well, with two zeros of copolarized reflection coefficient in the passband and two zeros of cross-polarized reflection coefficient in the stopband observed. The fractional bandwidth (FBW) is around 3%, and the mode conversion loss is around 0.6 dB with the copolarized reflection coefficient under -10 dB. Oblique incident cases are also investigated, and stable frequency responses can be achieved.