Ultrathin Independently Controllable Multiband Reflective Polarization Rotator

Inspired by frequency-selective surface (FSS) design, this letter presents a novel and simple design methodology for multiband reflective polarization rotators (RPRs), enabling independently controllable operating bands, and a compact unit cell. The main concept involves manipulating the current distribution of a loop resonator to convert linearly polarized incident waves into cross-polarized waves upon reflection. The RPR consists of three metal layers separated by two dielectric substrates, featuring a square loop on the top layer and a folded strip line in the middle layer connected by vias. Multiband operation can be achieved by adding extra loops to the top layer, with each loop controlling its own frequency band. As a proof of concept, a dual-band RPR was designed using two square loops on the top layer operating in the [2.02 to 2.26] GHz and [4.12 to 4.48] GHz ranges. The design was extended to a tri-band by adding a third loop, operating at [1.54 to 1.7] GHz, [3.35 to 3.7] GHz, and [5.1 to 5.45] GHz. Thorough discussions of current distribution analysis, and experimental demonstrations are provided. The simulated results are validated through prototype measurements, showing good agreement with experimental data.