Characteristic Mode Analysis of Split-Dipole for Dual-Layer Metasurface Lens Design

A split-dipole-based unit cell is modeled with characteristic mode analysis for the dual-layer metasurface lens at Ka-band. The split-dipole is first analyzed to show the modal behaviors over the operating band. Then the first two modes are selected for reflectionless incidence by rotating the split-dipole with a certain angle. After that, a planar unit cell is developed for substrate implementation with a magnitude of transmission coefficient better than 0.72 and a phase shift range of 360°. As an example, a dual-layer metasurface lens with an aperture size of 162 mm × 162 mm and a focal length of 135 mm is designed at 30 GHz. The achieved results show the peak gain of 31.6 dBi at 30 GHz with an aperture efficiency of 45% which well verified the proposed method. The metasurface lens can be realized on a single-layer substrate which shows great potential for low-cost communication and radar applications.