Quad-band and filtering linear polarization converter based on multi-mode metasurface

Abstract This article proposes a quad-band filtering linear polarization converter (LPC) based on a single multimode resonant metasurface unit. In contrast to the traditional designs with combined resonators, the proposed resonating unit is composed of a multimode cross-shaped patch resonator and a multi-mode slot-line resonator in an inlaid form. It can enable the excitation of these resonant modes and zeros from both resonators without increasing the overall size and complexity, thereby simultaneously realizing polarization conversion and multi-mode filtering effects in four passbands, as well as high isolation outside the bands. Mode analysis is utilized to demonstrate in detail the evolution of the unit cell, and the polarization conversion and passband adjustment properties are thoroughly illustrated. The proposed LPC achieves polarization conversion ratios (PCRs) exceeding 85% across four bands of 3.6–4.3 GHz, 8.1–10.9 GHz, 13.4–14.8 GHz, and 17.2–17.9 GHz, while maintaining nearly zero PCR outside these bands, showing the advantages of multi-band and good filtering characteristics. This LPC is promising for polarization control in complex electromagnetic environments to improve spectrum utilization.