Spherically-Conformed Loxodromic 3-D-printed Dielectric Polarizer for Dual-Circularly Polarized Omnidirectional Radiation in Ka-Band Vehicular Communications

In this contribution, the design of a 3D-printed spherically-conformed anisotropic dielectric polarizer is presented for millimeter-wave vehicular communication applications in the Ka-band. The proposed polarizer is comprised of dielectric slabs shaped in spherical arrangement whose profile follows the trajectory of a loxodromic curve. As a consequence, each slab is 45° and 135° tilted to the azimuthal and polar directions of a spherical coordinate system for all spatial directions, respectively, thus ensuring the existence of the necessary anisotropy to enable linear to circular polarization conversion for linearly polar and linearly azimuthal polarized incident spherical waves. When the polarizer is illuminated by an omnidirectional linearly polarized source, the polar/azimuthal linearly polarized spherical wave is converted into a left-hand circularly polarized (LHCP)/right-hand circularly polarized (RHCP) spherical wave, respectively. In this study, the proposed polarizer behavior is evaluated in the Ka-band (26–40 GHz). Furthermore, an experimental design is carried out in the upper range of the Ka-band (37 GHz – 40 GHz). An omnidirectional antenna exhibiting dual linear polarization, azimuthal and polar, is used as a feed to illuminate the sphericallyconformed polarizer comprised of loxodromic dielectric slabs. Thus, the resulting emitted radiation is RHCP when the feed antenna operates in its azimuthal polarization mode, and LHCP when the feed operates in its polar polarization mode. The polarizer and the feed antenna are printed by means of distinct 3D-manufaturing techniques. The measurements are in good agreement with the simulated results.