Rui Yuan Wu

Transmission-Type 2-Bit Programmable Metasurface for Single-Sensor and Single-Frequency Microwave Imaging.

The programmable and digital metamaterials or metasurfaces presented recently have huge potentials in designing real-time-controlled electromagnetic devices. Here, we propose the first transmission-type 2-bit programmable coding metasurface for single-sensor and single- frequency imaging in the microwave frequency. Compared with the existing single-sensor imagers composed of active spatial modulators with their units controlled independently, we introduce randomly programmable metasurface to transform the masks of modulators, in which their rows and columns are controlled simultaneously so that the complexity and cost of the imaging system can be reduced drastically. Different from the single-sensor approach using the frequency agility, the proposed imaging system makes use of variable modulators under single frequency, which can avoid the object dispersion. In order to realize the transmission-type 2-bit programmable metasurface, we propose a two-layer binary coding unit, which is convenient for changing the voltages in rows and columns to switch the diodes in the top and bottom layers, respectively. In our imaging measurements, we generate the random codes by computer to achieve different transmission patterns, which can support enough multiple modes to solve the inverse-scattering problem in the single-sensor imaging. Simple experimental results are presented in the microwave frequency, validating our new single-sensor and single-frequency imaging system.

High-Gain Dual-Band Transmitarray

We propose a novel linearly polarized, dual-band, and high-gain transmitarray based on multilayer frequency-selective surface structures. This is the first time for actualizing a dual-band transmitarray with more than 50% aperture efficiency. The unit cell is composed of four metallic layers without dielectric substrates between every two layers, which results in good match, low insertion loss, and high radiation efficiency. We introduce two kinds of rectangular slots in the design to control the magnitude and phase range of transmission coefficients in the two designed frequency bands through changing the slot length. The isolation between two bands is excellent and the interference can be ignored. The induced electric fields of the cell are also investigated in order to elucidate the working principle intuitionally. The proposed dual-band transmitarray with a square aperture (

Suboptimal Coding Metasurfaces for Terahertz Diffuse Scattering

240 \times 240

An ultrathin spiral phase plate for generation of OAM radio waves

mm

Large-scale transmission-type multifunctional anisotropic coding metasurfaces in millimeter-wave frequencies

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Transmission-Reflection-Integrated Multifunctional Coding Metasurface for Full-Space Controls of Electromagnetic Waves

) is designed, fabricated, and measured. A linearly polarized corrugated horn antenna is adopted to improve the aperture efficiency and ensure the similarity of the radiation patterns on E-plane and H-plane. Full-wave simulation and experimental results have very good agreements. It is demonstrated that the dual-band transmitarray works in two frequency bands 11.8–12.2 and 17.5–18.1 GHz simultaneously, and the peak gains in the designed central frequencies 12 and 18 GHz are 27.8 and 31.4 dB, respectively, which correspond to the aperture efficiencies (global efficiencies) of 52% and 53%. The proposed design has advantages of simple structure, small weight, low cost, and high performance, making it possible for real applications.

Polarization-selective dual-band digital coding metasurface for controls of transmitted waves

Coding metasurfaces, composed of only two types of elements arranged according to a binary code, are attracting a steadily increasing interest in many application scenarios. In this study, we apply this concept to attain diffuse scattering at THz frequencies. Building up on previously derived theoretical results, we carry out a suboptimal metasurface design based on a simple, deterministic and computationally inexpensive algorithm that can be applied to arbitrarily large structures. For experimental validation, we fabricate and characterize three prototypes working at 1 THz, which, in accordance with numerical predictions, exhibit significant reductions of the radar cross-section, with reasonably good frequency and angular stability. Besides the radar-signature control, our results may also find potentially interesting applications to diffusive imaging, computational imaging, and (scaled to optical wavelengths) photovoltaics.

Multitasking Shared Aperture Enabled with Multiband Digital Coding Metasurface

Recently, orbital angular momentum (OAM) has attracted much attention in radio frequencies due to the unique properties that radio waves carrying different OAMs are inherently orthogonal. Consequently, OAM-based multiplexing has potentials to increase the capacity of communication system. Here, a novel ultrathin slot-based planar-spiral phase plate (planar-SPP) is designed for generating the OAM radio waves. The proposed planar-SPP is designed using the concept of transmit array antenna with the ability to individually control the transmission phase of each element to generate the radio beams carrying OAMs with a specific topological charge. The unit cell used here consists of two identical components placed on top of each other. Each component is composed of two closely-placed thin dielectric layers, in which the outer layers are etched with annular ring slots and the inner layer is placed with a uniplanar compact photonic bandgap (UC-PBG) element. The UC-PBG element functions as an additional resonator and coupler to reduce the requirement of an extra layer. The proposed four-layer unit cell is compact with a total thickness of λ0/15 at the frequency of 10 GHz, which achieves a full transmission-phase range of 360° and transmission magnitude equal to or better than -1 dB. Besides, the phase error is less than 5° when the oblique incidence angle is less than 40°. Such a unit cell of superior performance ensures the proposed planar-SPP to have high efficiency. The simulated far-field radiation patterns and near-field phase distributions clearly show the generation of OAM-carrying radio waves, which verifies the feasibility of the proposed design. The planar-SPP has advantages of high efficiency and low profile, having potential applications in the radio communication systems.