Novel Design of Dual-/Tri-Band Polarization Rotation Surfaces Using Orthogonally Inserted Coupled Slotlines

Novel dual-/tri-band polarization rotation surfaces (PRSs) based on orthogonally inserted coupling slotlines are proposed, which can rotate a linearly polarized incident wave by 90°. The element of PRS comprises two coupling branches, and each branch is constructed by two coupled slotlines etched on the orthogonal printed circuit boards (PCBs). Under a vertically or horizontally polarized incident wave, the spatial wave is transformed into the guided wave by the end of one slotline and coupled to another slotline layered in the orthogonal direction, thus resulting in 90° polarization rotation. By approximately adjusting the coupling strength of the couped slotlines, dual-band and triband with second-order filtering responses can be achieved. Moreover, two extra straight slotlines are etched on the two orthogonal PCBs, respectively, to generate transmission zeros (TZs) to enhance the frequency selectivity between passbands. The simulation exhibit good dual-/tri-band filtering responses with sharp band edges, stable response characteristic for oblique angles of incidence, and high polarization conversion ratio (PCR).