Microwave vortex-beam generator based on corrugated metal–insulator–metal ground supported spoof surface plasmon polaritons

The vortex beam is an electromagnetic wave that carries orbital angular momentum (OAM). It has an infinite variety of orthogonal modes and provides a new method for increasing wireless communication channels and improving the resolution of radar imaging, therefore it has attracted more attention in recent years. In this paper, a vortex-beam generator is proposed, whose overall structure is made up of a series of circular radiation patches placed on a dielectric substrate and a ground plane, and the ground is composed of corrugated metal–insulator–metal (CMIM). The circular patches are radiating units that can also generate the phase shifts needed for the vortex beam, they are placed in different layers with the spoof surface plasmon polaritons (SSPPs) waveguide to enhance the coupled electric field. The CMIM structure functions both as a waveguide of SSPPs and as the ground plane. Reasonable design, numerical simulation, and experimental measurement show that the generator can generate left and right circularly polarized vortex beams with different OAM modes at different frequencies without changing the structure. And, the generator has many advantages, such as single feed, unidirectional, multi-mode, and small size, and it can be integrated into the system and integrated circuits more easily.