Characteristic Mode Inspired Dual-Polarized Double-Layer Metasurface Lens

In the following, we propose a dual-polarized double-layer metasurface lens based on split dipole unit cells. The characteristic mode analysis (CMA) of a split electric dipole shows two characteristic modes over the band of interest. By exciting these two modes with a certain phase difference, the reflection at normal incidence can be canceled. Inspired by this idea, a planar dual-polarized unit cell based on four pairs of split electric dipoles is designed on a single-layer substrate. A phase range of 396° and a transmission coefficient with a magnitude higher than 0.8 are achieved. For experimental verification, a metasurface lens with $36\times36$ elements is designed at 30 GHz with a focal diameter ratio of 0.84. The measured peak gain is 31.6 dBi at 31 GHz with an aperture efficiency of 45% and 1 dB/3 dB gain bandwidth of 7.3%/14%, respectively. Due to the dual-polarized operation, the relative high aperture efficiency, and the low-cost design, the proposed metasurface lens is a promising candidate for millimeter-wave communication, e.g., 5G and satellite communication systems.