Low-Profile Multiorder Reflective Polarization Rotator

This work presents a simple methodology for multiorder reflective polarization rotators (RPRs), enabling controllable order response without added unit cell complexity. The approach relies on manipulating current distributions and coupling between multiple resonators to convert linearly polarized incident waves into cross-polarized reflection. The structure comprises three metallic layers separated by two substrates, with a square loop resonator on the top layer and wrapped microstrip lines in the middle layer. The top and middle layers are connected via holes. Higher-order responses are realized by introducing additional resonators in the middle layer, each of which is coupled to generate the higher-order response. A basic second-order RPR design is extended to a third-order response utilizing two techniques. A fourth-order design is then accomplished by combining the two design techniques employed for the third-order response. The third-order designs achieved an effective working band in the regions 4.87 GHz to 5.56 GHz for the first design and 4.44 GHz to 5.39 GHz for the second design. While the fourth-order design is operating between 4.43 GHz and 5.3 GHz, which represents a fractional bandwidth of 17.9%. Detailed analysis of the proposed designs is included. A fabricated fourth-order prototype is measured to validate the simulated results. The experimental results show strong agreement with the simulations.