In this paper, transmitting metasurface using single dielectric substrate for orbital angular momentum (OAM) generation is presented in Ku band. A dimension extension method is introduced in designing the unit cell of the proposed transmitting metasurface to achieve required phase shift and transmission magnitude for generating OAM. A prototype of the proposed transmitting metasurface is fabricated and measured. Measured results suggest that the proposed transmitting metasurface can generate OAM vortex wave at 18 GHz. The proposed method can be applied in wireless communication systems requiring low-profile transmitted OAM generator.

In this paper, we present a novel design method to achieve optically transparent reflectarrays with fine metal line (FML) structure. With this design method, a reflectarray element with a peak return loss of 2.8 dB and a phase variation of 360° is achieved during 12.5-14.5 GHz. Compared with the reported transparent reflectarrays, we first realize wide phase variation, high transparency and low return loss simultaneously. The proposed element is composed of FML pattern, quartz glass substrate and ITO ground. The FML pattern is constructed of a metal cross and a folded square ring with a line width of 50 μm made by a photolithographic process. For verification, three 20×20-element reflectarrays with pencil beam and orbital angular momentum (OAM) beam have been arranged, simulated, fabricated and measured. The measured results agree well with the simulations. The measured optical transmittance of all prototypes is greater than 82% at any position. The proposed FML structure greatly improves the transmittance and has potential for the applications in transparent communication devices.

In this communication, a new method for modulating spin angular momentum (SAM) and orbital angular momentum (OAM) based on anisotropic holographic metasurfaces is proposed, which can realize the co-modulation of SAM, high order OAM, and beam’s direction simultaneously. The tensor unit adopts an ellipse patch with three adjustable parameters without slotting, and a design and analysis method suitable for this kind of tensor unit is proposed based on the two-dimensional effective impedance database for geometrical size mapping. Based on the tensor unit and proposed methods, the vortex beams with a single SAM state, a single high order OAM mode, and different directions are generated at 22 GHz. Then, the deflected vortex beams with the same SAM state and mixed OAM modes, or the deflected vortex beams with different SAM states and OAM modes are realized using a single feed and a single metasurface integrated for the first time. Simulation and experimental measurement results show that the OAM mode purity can reach more than 80% of the theoretical best value in the main SAM state. The proposed design methods and the device can achieve arbitrary modulation of SAM and OAM, providing a solution for combining and applying the two to multiplexing communications.

This letter presents a fixed-frequency beam-steering leaky-wave antenna (LWA) with switchable beam number. The proposed LWA consists of an impedance modulation surface (IMS) and dc bias circuit. A three-strip structure is designed as the unit cell of the IMS. In this design, varactor diodes are inserted in the unit cell and the impedance characteristics of every unit cell can be controlled independently. Both average reactance and modulation periodicity of the IMS can be tuned for leaky-wave radiation with different beam angle. The proposed LWA can be configured to work in single-beam mode or dual-beam mode. A prototype of the proposed LWA operating at 8 GHz is fabricated and measured. By controlling the dc voltages of varactor diodes, a scanning range of 118° can be achieved.

A holographic design of beam-switchable leaky-wave antenna (LWA) is presented. The proposed design consists of a holographic impedance modulated surface (HIMS) and control circuit. In this design, the HIMS, which carries impedance characteristics of four beams, is obtained by using a modified modulation method in the same aperture. Thus, the proposed HIMS can generate four switchable beams at a fixed frequency when itis excited by different reference waves. By controlling p-i-n diodes inserted along the feedline, four working states can be obtained. The proposed LWA is fabricated and measured. Four switchable beams with pitch angles of θ ₁ = θ ₂ = -30°, θ ₃ = θ ₄ = 30° and azimuth angles of φ ₁ = 0°, φ ₂ = 90°, φ ₃ = 180°, and φ ₄ = 270° are obtained at 18 GHz. The measured peak gain of each beam is better than 17.2 dBi.

In this Letter, an active second-order frequency-selective surface (AFSS) that features a switchable wide pass-band is proposed. Compared to other multi-layer feeding structures, only one layer of FSS is elaborately reconfigured in this design, whose full planar symmetry structure is not destroyed, to achieve the desired all-polarized controlled behavior. The presented design provides good responses under different incident angles and polarizations. The fulfilled structure is composed of three FSS layers and is controlled by semiconductor switches. When the switches are in OFF-state, the proposed design acts as a high-transmittance second-order filter with a low ripple level, whose -0.5 dB passband width is over 24.4% and minimum insertion loss is only 0.1 dB. By switching the semiconductors to ON-state, the unit cells of the top FSS layer are short-connected, which leads to an ultra-wideband shielding behavior from 0 to 10 GHz. Moreover, the proposed structure presents consistent responses under 0°-90° rotation polarizations. Both filter and shielding responses can be obtained up to the 60° incidence. Finally, a prototype is fabricated and measured, and the desired wideband, high-efficiency, wide-angle, and polarization-insensitive switchable performances are obtained through equivalent-circuit calculations, numerical simulations, and experimental measurements.