Field trial measurement and channel modeling for reconfigurable intelligent surface

With the advantage of programmable electromagnetic properties,Reconfigurable Intelligent Surfaces(RISs)havedrawn wide attention from both industry and academia.RIS-assisted communication systems can promote hugewireless channel quality improvement and remarkable coverage enhancement.This paper proposes generalpathloss model,radiation pattern and mirror beam effect of 1-bit RIS at sub-6 GHz band.Field trails have beencarried out in outdoor and indoor deployment scenarios.The proposed model is validated through extensivesimulations and field-trial measurements.In addition,an optimized RIS phase-shit design process for the mirrorbeam elimination is proposed and validated with simulations.The proposed theoretical model and measurementresults can promote future research and application in RIS-assisted communications.

Predictive Tracking Implementation for Mobile Communication Using Programmable Metasurface

The programmable metasurface(PM)is an antenna array architecture that realizes flexible beam steering.This functionality is achieved by controlling the unit cells designed with micro components such as positive-intrinsic-negative(PIN)diodes,which offers potential cost reductions in the next generation wireless communication systems.Although PM has been a popular topic in antenna design,its implementations in real-time systems accompanied by signal processing algorithms are challenging.In this paper,novel predictive tracking algorithms for mobile communication scenarios using a PM are created and implemented in a real-time system operating at 28 GHz.An angular speed prediction(ASP)algorithm is proposed to compute the position of user equipment(UE)based on the previously recorded beam directions.As another solution,an angle correction(AC)algorithm is proposed to further improve the prediction and tracking accuracy.As a benchmark,the comparisons to a previous PM tracking algorithm without prediction are presented.Both simulation and measurement results show that the prediction algorithms successfully improve the tracking performance,which also prove the feasibilities of PM-based systems to solve complex real-time signal processing problems.

Joint Modulations of Electromagnetic Waves and Digital Signals on a Single Metasurface Platform to Reach Programmable Wireless Communications

In current wireless communication and electronic systems,digital signals and electromagnetic(EM)radiation are processed by different modules.Here,we propose a mechanism to fuse the modulation of digital signals and the manipulation of EM radiation on a single programmable metasurface(PM).The PM consists of massive subwavelength-scale digital coding elements.A set of digital states of all elements forms simultaneous digital information roles for modulation and the wave-control sequence code of the PM.By designing digital coding sequences in the spatial and temporal domains,the digital information and farfield patterns of the PM can be programmed simultaneously and instantly in desired ways.For the experimental demonstration of the mechanism,we present a programmable wireless communication system.The same system can realize transmissions of digital information in single-channel modes with beamsteerable capability and multichannel modes with multiple independent information.The measured results show the excellent performance of the programmable system.This work provides excellent prospects for applications in fifth-or sixth-generation wireless communications and modern intelligent platforms for unmanned aircrafts and vehicles.

Circular Polarization Hologram Realized by Pancharatnam-Berry Phase in Microwave Frequency

Metasurfaces have shown great potential in controlling the propagation of electromagnetic waves, making them suitable for holographic beam-shaping elements. Using the principle of array synthesis, holograms have been realized in microwave frequency to manipulate electromagnetic waves to generate specific field patterns. However, current research is almost based on linear polarization and has little analysis on the circular polarization microwave hologram. Herein, we propose a circular polarization hologram realized by sub-wavelength units with self-adaptively phase profiles of electromagnetic waves. The full, continuous control of the phase is achieved by using a single structure unit based on the Pancharatnam-Berry phase. The inhomogeneity of wave-front is considered through amplitude and phase compensation which are essential to improve the quality of microwave hologram. The model achieves circular polarization hologram in microwave frequency and the clear field pattern is generated. The circular polarization hologram enriched the research field of microwave imaging, thus providing more inspirations for the development of various related techniques.

Edge Device Fault Probability Based Intelligent Calculations for Fault Probability of Smart Systems

In a smart system, the faults of edge devices directly impact the system’s overall fault. Further, complexity arises when different edge devices provide varying fault data. To study the Smart System Fault Evolution Process (SSFEP) under different fault data conditions, an intelligent method for determining the Smart System Fault Probability (SSFP) is proposed. The data types provided by edge devices include the following: (1) only known edge device fault probability;(2) known Edge Device Fault Probability Distribution (EDFPD);(3) known edge device fault number and EDFPD;(4) known factor state of the edge device fault and EDFPD. Moreover, decision methods are proposed for each data case. Transfer Probability (TP) is divided into Continuity Transfer Probability (CTP) and Filterability Transfer Probability (FTP). CTP asserts that a Cause Event (CE) must lead to a Result Event (RE), while FTP requires CF probability to exceed a threshold before RF occurs. These probabilities are used to calculate SSFP. This paper introduces a decision method using the information diffusion principle for low-data SSFP determination, along with an improved method. The method is based on space fault network theory, abstracting SSFEP into a System Fault Evolution Process (SFEP) for research purposes.

Electromagnetic Metamaterials:From Classical to Quantum

Electromagnetic(EM)metamaterials are artificially engineered materials with extraordinary EM properties beyond the limit of existing nat-ural materials;thus,they have been widely used to manipulate the amplitude,phase,polarization,frequency,wave vector,waveform,and other degrees of freedom of EM waves in many practical applications.In this review,we will summarize recent advances in this flourishing field of EM metamateri-als,first from the perspectives of the classical regime and then the quantum regime.More specifically,in the classical regime,traditional EM metamate-rials are based on effective medium theory,and they have limitations of fixed functionalities and an inability to control EM waves in real time.To over-come these restrictions,information metamaterials,including digital coding and field-programmable metamaterials,have recently been proposed to en-able real-time manipulation of EM waves based on the theory of information science.By taking advantage of information metamaterials and artificial in-telligence,another crucial milestone of intelligent metamaterials has been achieved in the development of classical metamaterials.After overviewing EM metamaterials in the classical regime,we discuss cutting-edge studies of EM metamaterials in the quantum regime,namely,topological metamaterials and quantum metamaterials.These nonclassical metamaterials show excellent ability to flexibly manipulate the quantum states,and they extend the clas-sical information metamaterials into the field of quantum information science.At the end of this review,we will give some conclusions and perspectives on this fast-evolving field.

Transparently curved metamaterial with broadband millimeter wave absorption

We present a conformal metamaterial with simultaneous optical transparency and broadband millimeter-wave absorption for a curved surface. By tailoring the reflection response of meta-atoms at oblique angles, it is possible to achieve excellent absorption performance from 26.5 to 40.0 GHz within a wide angular range from 0° to 60°for transverse-electric and transverse-magnetic waves. In the meantime, by employing transparent substrates,including polyvinyl chloride and polyethylene terephthalate, good optical transmittance(80.1%) and flexibility are obtained simultaneously. The reflectivity of a curved metallic surface coated with the proposed curved metamaterial is simulated and measured experimentally. Both results demonstrate excellent absorption performance of the metamaterial, which is highly favored for practical applications.

Broadband transmission-type 1-bit coding metasurface for electromagnetic beam forming and scanning

Coding metasurfaces make it possible to manipulate electromagnetic(EM)waves digitally by means of several discrete particles.Hence,there have been rapid advances in this field recently.Here we propose a novel design of a broadband transmission-type coding metasurface,which is valid to both x-and y-polarized EM incidences from 8.1-12.5 GHz while satisfies the requirements of 1-bit coding without changing the polarization.Two types of multi-layer coding particles with different geometrical parameters are adopted to represent the digital states"0"and"1",which are easily promoted to terahertz and optics through modifying the size scale.To verify the ability to manipulate the EM waves,we first adopt the coding metasurface to achieve broadband beam forming by converting spherical waves to plane waves and realize high-directivity pencil beam in far field with low side lobes.We further arrange the particles according to the coding sequence 010101…to steer two symmetrical beams in different directions controlled by frequencies with the maximum range of the scanning angle of 30°-50.5°.The good agreements between the simulated and measured results validate the proposed broadband coding metasurface,indicating its huge potential in communication and radar imaging systems.

Electromagnetic metasurfaces: from concept to applications

Electromagnetic or optical metasurfaces, as a kind of quasi-twodimensional artificial interface, are patterned subwavelength structures within ultrathin thickness that interact strongly with electromagnetic waves. The history of metasurface was traced back to the two-dimensional electromagnetic bandgap structure [1], which may be regarded as the beginning of metasurface research. Such metasurface with high impedance has been widely used in reducing the size of antennas and improving their performance. Recently, generalized Snell’s laws [2] have been coined and widely applied to various designs of metasurfaces [3], which pave a clearcut physical foundation for metasurfaces. Thereby, the metasurfaces have been widely deployed in designing new devices to regulate and control the electromagnetic wavefronts. For example, 600-nm-thick TiO2 metalens have been demonstrated to focus the light [4], 105 times thinner than the optical traditional lens with similar performance. Such a metasurface lens is believed promising to replace the traditional optical lens in the future. Hence, functional structured surfaces have become the subject of several rapidly-growing research areas, and demonstrated a lot of useful properties of structure-based devices with customized electric and magnetic responses.

Chirality Enhancement Using Fabry-Pérot-Like Cavity

Chiral molecules that do not superimpose on their mirror images are the foundation of all life forms on earth.Chiral molecules exhibit chiroptical responses,i.e.,they have different electromagnetic responses to light of different circular polarizations.However,chiroptical responses in natural materials,such as circular dichroism and optical rotation dispersion,are intrinsically small because the size of a chiral molecule is significantly shorter than the wavelength of electromagnetic wave.Conventional technology for enhancing chiroptical signal entails demanding requirements on precise alignment of the chiral molecules to certain nanostructures,which however only leads to a limited performance.Herein,we show a new approach towards enhancement of chiroptical effects through a Fabry-Pérot(FP)cavity formed by two handedness-preserving metamirrors operating in the GHz region.We experimentally show that the FP cavity resonator can enhance the optical activity of the chiral molecule by an order of magnitude.Our approach may pave the way towards state-of-the-art chiral sensing applications.