In this paper, a reflective metasurface is designed, fabricated, and experimentally demonstrated to generate an orbital angular momentum (OAM) vortex wave in radio frequency domain. Theoretical formula of phase-shift distribution is deduced and used to design the metasurface producing vortex radio waves. The prototype of a practical configuration is designed, fabricated, and measured to validate the theoretical analysis at 5.8 GHz. The simulated and experimental results verify that the vortex waves with different OAM mode numbers can be flexibly generated by using sub-wavelength reflective metasurfaces. The proposed method and metasurface pave a way to generate the OAM vortex waves for radio and microwave wireless communication applications.

In this paper, an electromagnetic metasurface is designed, fabricated, and experimentally demonstrated to generate multiple orbital angular momentum (OAM) vortex beams in radio frequency domain. Theoretical formula of compensated phase-shift distribution is deduced and used to design the metasurface to produce multiple vortex radio waves in different directions with different OAM modes. The prototype of a practical configuration of square-patch metasurface is designed, fabricated, and measured to validate the theoretical analysis at 5.8 GHz. The simulated and experimental results verify that multiple OAM vortex waves can be simultaneously generated by using a single electromagnetic metasurface. The proposed method paves an effective way to generate multiple OAM vortex waves in radio and microwave wireless communication applications.

This paper presents a new design of near-field focused metasurface for high-efficiency wireless power transfer with multi-focus characteristics. A general synthesis procedure is outlined to design metasurfaces with desired multiple foci in the near-field zone. The unit cell of printed tri-dipole is used to realize the focused metasurface which has a large range of phase shift and is adapted to near-field focusing applications. Different feeding and focusing designs of the printed tri-dipole metasurfaces are proposed and analyzed. Two kinds of metasurfaces with 20-20 elements are designed, fabricated and measured at 5.8 GHz. One is the single-feed and single-focus case, and the other is single-feed and two-focus case. Two-dimensional planar near-field scanning technique is implemented to measure the E-field focusing characteristics. Full-wave simulations and experiments demonstrate that the proposed focusing metasurfaces have a high wireless power transfer efficiency of 70%. The relative bandwidth with 50% power focusing efficiency is about 16%. The measured results are in good agreement with the theoretical designs and simulated results, which verify the feasibility and correctness of the proposed approach in this paper.

A metasurface, which is composed of printed cross-dipole elements with different arm lengths, is designed, fabricated, and experimentally demonstrated to generate orbital angular momentum (OAM) vortex waves of dual polarizations and dual modes in the radio frequency domain simultaneously. The prototype of a practical metasurface is fabricated and measured to validate the results of theoretical analysis and design at 5.8 GHz. Numerical and experimental results verify that vortex waves with dual OAM modes and dual polarizations can be flexibly generated by using a reflective metasurface. The proposed method paves a way to generate diverse OAM vortex waves for radio frequency and microwave wireless communication applications.

A novel reconfigurable polarization conversion method based on a metasurface turned by PIN diodes is proposed herein. The proposed metasurface consists of one layer of a dielectric and two layers of metal surfaces. When the diode is in an OFF-state, a wideband linear to circular (LTC) polarization converter is realized. The results show that the metasurface can achieve LTC polarization conversion in the frequency range of 11.8-24.1 GHz, and the axial ratio (AR) reveals that the 3-dB bandwidth is approximately 68.5%. When the diode is in the ON-state, a dual-band linear to linear (LTL) polarization converter is realized, with the 3-dB bandwidths of 10.5-13.9 GHz and 17.7-27.2 GHz, achieving a polarization converter ratio (PCR) greater than 90%. The dc bias circuit of the PIN diode is etched on the reflectance surface. Therefore, no additional feeding lines are introduced, which can decrease the impact on the active metasurface; this metasurface has practical applications in microwave communication systems.

A high-order Bessel vortex beam carrying orbital angular momentum (OAM) is generated by using multilayer amplitude-phase-modulated surfaces (APMSs) at 10 GHz. The APMS transmitarray is composed of four-layer conformal square-loop (FCSL) surfaces with both amplitude and phase modulation. The APMS can transform a quasi-spherical wave emitted from the feeding source into a pseudo non-diffractive high-order Bessel vortex beam with OAM. The APMS for a second-order Bessel beam carrying OAM in the n = 2 mode is designed, fabricated, and measured. Full-wave simulation and measurement results confirm that Bessel vortex beams with OAM can be effectively generated using the proposed APMS transmitarray.