A Wideband Millimeter-Wave Circularly Polarized Metal Lens

This paper presents a design of a wideband circularly polarized (CP) metal lens for millimeter-wave applications. The element is designed based on a quadruple-ridged waveguide which can realize the polarization conversion from CP to CP but with the opposite handedness, therefore enabling a full 360 degrees geometric phase controlled by the rotation of the ridges. For validation, a metal lens which can generate vortex beam with OAM mode of l = +1 is designed and simulated. The results show that a wide bandwidth can be obtained, and the mode purity of the generated vortex beam is as high as 0.99. Compared with conventional metal lens, the proposed work can obtain a wider axial ratio (AR) bandwidth since the CP performance can be improved by the geometric phase compensation. Moreover, the proposed element is also suitable for the design of a dual CP lens.