Search

Abstract The powerful capability of reconfigurable intelligent surfaces (RISs) in tailoring electromagnetic waves and fields has put them under the spotlight in wireless communications. However, the current designs are criticized due to their poor frequency selectivity, which hinders their applications in real-world scenarios where the spectrum is becoming increasingly congested. Here we propose a filtering RIS to feature sharp frequency-selecting and 2-bit phase-shifting properties. It permits the signals in a narrow bandwidth to transmit but rejects the out-of-band ones; meanwhile, the phase of the transmitted signals can be digitally controlled, enabling flexible manipulations of signal propagations. A prototype is designed, fabricated, and measured, and its high quality factor and phase-shifting characteristics are validated by scattering parameters and beam-steering phenomena. Further, we conduct a wireless communication experiment to illustrate the intriguing functions of the RIS. The filtering behavior enables the RIS to perform wireless signal manipulations with anti-interference ability, thus showing big potential to advance the development of next-generation wireless communications.

Previously proposed array antennas with low side-lobe level (SLL) based on amplitudephase metasurface inevitably result in high cross-polarization level (CPL) due to amplitude modulation is achieved by transforming some primary energy to the cross-polarization. This paper proposes a dualband circularly-polarized (CP) transmitarray antenna (TA) with simultaneous low SLL and CPL. The proposed antenna is based on a metasurface with independent amplitude and phase control at dual-band. The element of metasurface consists of dual-band receiver-transmitter (Rx-Tx) structures constructing CP receiving patches and transmitting patches. The amplitude and phase modulations at each band can be achieved dependently by adjusting the impedance-matching characteristics and the rotation angles of the Tx patches, respectively. By applying amplitude-phase modulation at dual-band, the antenna can achieve high directivity, low SLL and CPL simultaneously. Experimental results are in good accordance with the simulation ones, demonstrating that the designed low-side-lobe antenna realizes gains of 24.2 dBic and 25.2 dBic, CPLs of -32.2 dB and -26.6 dB, SLLs of -23.2 dB and -24 dB at 12 GHz and 15 GHz, respectively. The proposed TA shows good SLL and CPL performances at dual-band for dual-CP, which presents great application potential in two-way satellite communication systems with limited volume and space.

Abstract Hand gesture plays an important role in many circumstances, which is one of the most common interactive methods in daily life, especially for disabled people. Human–machine interaction is another popular research topic to realize direct and efficient control, making machines intelligent and maneuverable. Here, a special human–machine interaction system is proposed and namedas computer‐vision (CV) based gesture‐metasurface interaction (GMI) system, which can be used for both direct beam manipulations and real‐time wireless communications. The GMI system first needs to select its working mode according to the gesture command to determine whether to perform beam manipulations or wireless communications, and then validate the permission for further operation by recognizing unlocking gesture to ensure security. Both beam manipulation and wireless communication functions are validated experimentally, which show that the GMI system can not only realize real‐time switching and remote control of different beams through gesture command, but also communicate with a remote computer in real time by translating the gesture language to text message. The proposed non‐contact GMI system has the advantages of good interactivity, high flexibility, and multiple functions, which can find potential applications in community security, gesture‐command smart home, barrier‐free communications, and so on.

We propose a compact and high isolation dual-polarized antenna array based on plasmonic meta-structure operating at 2.58 GHz. The compact principle of the dual-polarized antenna is mainly based on spoof surface plasmon polariton (SSPP) radiation patch to support SSPP modes, which is fed by spatially coupled excitation. Due to the slow-wave feature of SSPPs, the size of dual-polarized radiation patch is reduced to $0.2\lambda _{0}\times 0.2\lambda _{0}$ , and the total antenna size is reduced to $0.39\lambda _{0}\times 0.39\lambda _{0}$ , which is much smaller than that of the traditional microstrip antenna with $0.5\lambda _{0}\times 0.5\lambda _{0}$ . The cross-polarization coupling between two polarization ports can be improved to below −32 dB, showing high isolation characteristics. Besides, a $3\times 3$ compact antenna array is also designed, fabricated, and measured to verify the feasibility of its extension to larger-scale antenna systems. Both simulated and measured results of the proposed compact antenna and the antenna array illustrate compact profiles, good ±45° radiation performance, and high isolation levels, which have potential application values for the massive multiple-input and multiple-output (MIMO) base stations.

Reconfigurable intelligent surfaces (RISs) have attracted extensive attention in recent years due to their strong ability to improve and customize electromagnetic wave propagation channels in wireless communications. In this article, we propose a design procedure for an RIS and its programmable element, whose reflection phase and amplitude can be jointly controlled by adjusting the states of the varactor and PIN-diode. In addition, by introducing metallic vias in the RIS element, the programmable element can maintain the stable reflection amplitude and phase responses under the illumination of transverse magnetic (TM) wave with the incident angle of 0–60°. In order to verify the beam steering performance of the RIS, theoretical calculations and full-wave simulations of single beam and dual beams are carried out according to the addition theorem of the complex reflection coefficient. The amplitude- and phase-coding patterns on the RIS array are well designed so that the deflection angles and power intensities of the scattered beams can be manipulated independently.

New dual‐beam leaky‐wave radiations based on spoof surface plasmon polariton (SSPP) waveguide, in which the amplitude, radiation, angle and polarization of each beam can be designed independently, is proposed. The proposed SSPP waveguide is made of a corrugated metallic strip with bilateral 45°‐tilted grooves, whose surface impedance is flexibly designed by changing the depth of grooves. To realize dual‐beam leaky‐wave radiations, the surface impedance of SSPP waveguide is modulated periodically based on the superposition theory of aperture fields. By simply adjusting the modulation factors, modulation periods, and initial phase differences of the modulated surface impedance, the amplitude, radiation angle, and polarization of each beam can be further controlled independently as well. The results have been validated by both numerical simulations and experimental measurements, which show good agreement with the theoretical predictions.

The efficient production of hydrogen through electrocatalytic decomposition of water has broad prospects in modern energy equipment. However, the catalytic efficiency and durability of hydrogen evolution catalyst are still very deficient, which need to be further explored. Here in this work, we prove that introducing a graphene layer (Gr) between the molybdenum disulfide and nickel foam (Ni–F) substrate can greatly improve the catalytic performance of the hybrid. Owing to the excitation of local surface plasmon resonance (LSPR) of gold nanoparticles (NPs), the electrocatalytic hydrogen releasing activity of the MoS2/Gr/Ni–F heterostructure is greatly improved. This results in a significant increase in the current density of AuNPs/MoS2/Gr/Ni–F composite material under light irradiation and in the dark at 0.2 V (versus reversible hydrogen electrode (RHE)), which is much better than in MoS2/Gr/Ni–F composite materials. The enhancement of hydrogen release can be attributed to the injection of hot electrons into MoS2/Gr/Ni–F by AuNPs, which will improve the electron density of MoS2/Gr/Ni–F, promote the reduction of H2O, and further reduce the activation energy of the electrocatalyst hydrogen evolution reaction (HER). We also prove that the introduction of graphene can improve its stability in acidic catalytic environments. This work provides a new way of designing efficient water splitting system. [ABSTRACT FROM AUTHOR]

BACKGROUND: Macamides, the main active components contained in maca, have attracted increasing attention due to their various bioactivities. In this study, crude macamide extract (CME) and purified macamide extract (PME) were prepared by enzyme‐assisted extraction and macroporous resin separation, and the anti‐fatigue effects of CME and PME were evaluated in a forced swimming model. RESULTS: The composition analysis results revealed that both CME and PME mainly contain eight kinds of macamide. Based on the results of a weight‐loaded forced swimming test, compared with a control group, CME and and PME groups could prolong exhaustive swimming time, increase levels of liver glycogen (LG) and muscle glycogen (MG), accelerate fatty acid oxidation in serum to provide energy, eliminate the accumulation of blood lactic acid (BLA) and blood urea nitrogen (BUN), and decrease the serum biomarkers for muscle damage, such as lactate dehydrogenase (LDH) and creatine kinase (CK). Histological analysis also indicated that CME and PME attenuated damage to skeletal muscle and the myocardium in mice during exercise. CONCLUSION: Two macamide extracts have a beneficial effect on relieving physical fatigue by attenuating the damage of skeletal muscle and myocardium during exercise, and a better effect was observed in the PME group. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]