Highly efficient polarization converter with wide angular stability.

This paper presents a multi-band polarization converter using spoof surface plasmon polaritons (SSPP), addressing the growing demand for efficient polarization control in modern communication systems, radar, and sensing technologies. By applying a spatial distribution to the SSP structure, we achieve high efficiency. The anisotropic design for x- and y-polarized waves enables independent control of the transmission phase, resulting in a wide frequency range of dispersive phase differences. This allows for different polarization states based on the incident wave's polarization direction. It is found that linear-to-circular polarization conversion is realized at frequencies of 4 GHz, 10 GHz, 13.5 GHz, and 15.54 GHz. Moreover, a circularly polarized incident wave can be converted to its orthogonal state at frequencies of 7.5 GHz and 14.8 GHz. Similarly, cross-polarization of linearly polarized incident waves is achieved at 7.5 GHz and 14.8 GHz. To verify the dispersion mechanism of the presented structure, the equivalent circuit method has been employed. A prototype of the structure has been fabricated to validate the results of numerical simulations. The experimental and simulation results confirm that the proposed structure is capable of achieving various polarization conversions, including linear-to-circular (circular-to-linear), linear-to-linear, and circular-to-circular. This work provides a versatile solution for multi-band polarization control across key frequency bands such as the C-band, X-band and Ku- band, which are essential for advanced communication, radar, and sensing applications.