Multimode OAM beam generation through 1-bit programmable metasurface antenna.

modern wireless communication, the orbital angular momentum (OAM) beam is considered as an important technology. Some considerable efforts have been devoted to using this technology for channel capacity enhancement as much as possible. Nowadays, programmable metasurfaces provide an innovational scenario for generating multi-mode OAM beams due to their ability for digital electromagnetic waves modulation. However, the current programmable metasurfaces for generating OAM beams are typically based on reflective and transmissive modes, which have low aperture efficiency due to spillover and illumination effects. In this paper, a 1-bit programmable metasurface antenna is proposed with capability of producing highly efficient dynamic multi-mode OAM beams. The proposed structure is consisted of electronically reconfigurable meta-radiating elements loaded by PIN diodes to generate two-phase states of electric field. The designed Field Programmable Gate Array (FPGA) can assign a code sequence of 0 or 1 to the metasurface antenna in real-time to generate multi-mode OAM beams. Hence, a dynamical surface is obtained by switching PIN diodes to change the phase distribution on the surface. To verify the concept, the metasurface antenna is fabricated and measured with different OAM beam states, which are in agreement with the full-wave simulations, properly. The designed structure introduces a capable multi-mode OAM alternative for high throughput mm-wave communications.