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To analyze the system safety through the field system operation data, especially the system operation information provided by the operators, and to obtain the environment scope of the safe operation of the system, the multi-attribute safety information intelligent mining method is adopted. The new definitions and methods of attribute circle classification are proposed. The improvement is using inner attribute polygon and outer attribute polygon to construct the object attribute area. Monte Carlo method is used to calculate the overlap area of the object attribute area, and define overlap and transform with similarity, which is calculated by the overlap degree and the distance between two points in multi-dimensional space. The object classification reasoning method and system adaptive environment analysis method is established. The improved similarity analysis method is more suitable for computer implementation and intelligent analysis. Based on the previous study, this paper also analyzes the similarity of operation safety evaluation given by 30 operators of an electrical system, and obtains the pair wise similarity. The results show that the algorithm classification results have good correspondence with the original data decision level, and the range of the system safe operation environment is obtained, which can lay a foundation for further study of intelligent classification and system safety operation environment optimization. more...

Reconfigurable intelligent surface (RIS) is a radical and cost-efficient technology to improve energy efficiency and mitigate interference in the heterogeneous network. In this paper, the resource allocation problem of sub-channels, transmit power and RIS coefficients is investigated in the RIS-aided heterogeneous network. To solve the formulated mixed integer nonlinear programming problem, a two-step centralized resource allocation algorithm and a two-step distributed resource allocation algorithm are proposed based on the alternating optimization method. In the centralized algorithm, the sub-channel allocation, transmit power and RIS coefficients are optimized by the macro base station solely, where the non-convex power optimization problem is transformed into a convex one based on the convex approximation method. In the distributed algorithm, which aims to alleviate the computational burden of the macro base station, the sub-channel allocation and transmit power are optimized by using the cooperation of all the small base stations and the macro base station. Finally, numerical results are presented to demonstrate the convergence of the proposed algorithms and the effectiveness of the sub-channel transfer. More importantly, it is shown that the centralized algorithm can achieve the higher total throughput, while the distributed algorithm greatly decreases the resource allocation time. more...

Near-field computational imaging has been recognized as a promising technique for nondestructive and highly accurate detection of the target. Meanwhile, reconfigurable intelligent surface (RIS) can flexibly control the scattered electromagnetic (EM) fields for sensing the target and can thus help computational imaging in the near field. In this article, we propose a near-field imaging scheme based on holographic aperture RIS for both 2-D and 3-D targets. Specifically, we first establish an end-to-end EM propagation model from the perspective of Maxwell equations. To mitigate the inherent ill-conditioning of the inverse problem in the imaging system, we design the EM field patterns as masks that help translate the inverse problem into a forward problem. Next, we utilize RIS to generate different virtual EM masks on the target and calculate the cross correlation between the mask patterns and the electric field strength at the receiver. We then provide a RIS design scheme for virtual EM masks by employing a regularization technique. The cross-range resolution of the proposed method is analyzed based on the spatial spectrum of the generated masks. Simulation results demonstrate that the proposed method can produce satisfactory imaging results for both 2-D and 3-D targets. Moreover, the imaging quality can be improved by generating more virtual EM masks, increasing the signal-to-noise ratio (SNR) at the receiver, or placing the target closer to the RIS. more...

As protective apparatus, electromagnetic windows (EMWs) are usually realized utilizing dielectric materials with higher permittivity or larger thickness to perform good mechanical properties. However, due to impedance mismatch, higher insertion loss is inevitably created, especially at large incident angles. It is now still a great challenge to engineer EMWs with stable operating bands and a wide range of incident angles for both transverse electric (TE)- and transverse magnetic (TM)-polarizations. In this article, we propose a method to achieve such EMWs by the synergy of multimechanism resonances, which enables broadband transmissions of both TM- and TE-polarized waves in an ultrawide range of incident angles. Fano resonance is first introduced to expand the bandwidth for TE-polarization on the basis of thickness resonance. Drude resonances are then introduced to suppress adverse influences of the parasitic Lorentz resonance for TM-polarization, to maximize the shared transmission band for TM- and TE-polarizations. The ultrawide-angle broadband functionalities of this EMW are validated by experiments, which agree well with numerical simulations. This work provides an efficient route to realize practical high-performance EMWs, under sufficient consideration of available materials, structures, and fabrication techniques, which may find wide applications in radar, communication, and imaging systems. more...

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. more...

In the conventional routes to obtain stealth array antennas, various techniques are used to reduce the radar cross sections (RCSs) of existing antennas based on experience-relying trial-and-error and time-consuming optimizations. To address the issue, we propose reverse thinking, i.e., low scattering performance precedes radiation performance, and present a universal and definite route to achieve low-RCS array antennas directly from metasurfaces rather than from antennas. A specific design method is carefully elaborated to illustrate this route. First, a low RCS metasurface is designed. Then an interdigital arrangement of the metasurface and proper feeding techniques are exploited to excite parts of the metasurface cells to produce efficient radiations. These partially excited cells play twofold roles as the radiating structures for array antenna and as part of scattering structures for the low-RCS property. As examples, 1-D and 2-D metasurface-based array antennas are elaborately designed and fabricated, in which good radiation performance and broadband low RCSs are achieved simultaneously. Both numerical simulations and experimental results verify the effectiveness of the proposed method. It suggests that the proposed route is more likely to speed up the design process and yield an integration structure and controllable performance. more...

Integrating active and passive manipulation of electromagnetic (EM) waves has significant advantages for the caliber synthesis of microwave and optical integrated devices. In previous schemes, most reported designs focus only on active ways of manipulating self-radiating EM waves, such as antennas and lasers, or passive ways of manipulating external incident EM waves, such as lenses and photonic crystals. Here, we proposed a paradigm that integrates active and passive manipulation of EM waves in a reconfigurable way. As demonstrated, circularly polarized, linearly polarized, and elliptically polarized waves with customized beams are achieved in passive operation by merging Pancharatnam–Berry phases and dynamic phases, while the radiating EM waves with a customized gain are achieved by coupling the coding elements with the radiation structure in the active manipulation. Either active or passive manipulation is determined by the sensed signals and operating state to reduce detectability. Encouragingly, the proposed strategy will excite new sensing and communication opportunities, enabling advanced conceptions for next-generation compact EM devices. more...

In the process of system operation, the ability to complete the predetermined function is changing, which is uncertain for the system designer. In order to study the uncertainty of system function state, the causes of uncertainty are analyzed with the help of system fault evolution process and space fault network theory, and the methods to deal with and express uncertainty are studied. Firstly, human, man-made system and natural system are defined; Secondly, the four elements of evolution structure are obtained through space fault network; the causes of uncertainty are factor, data and cognition; the method to deal with uncertainty is analyzed by using four factors; finally, a method to represent the uncertainty of system function state is proposed. According to the research, man-made system is a system established by man according to his subjective cognition, which can complete the predetermined function, that is, man's cognition determines man-made system. Due to the loss of factor flow and data flow in the transmission process, people's cognition of natural system is limited. There must be differences between man-made system and natural system, which is the uncertainty of system function state. more...