Efficient Synthesis of Passively Loaded Finite Arrays for Tunable Anomalous Reflection

A design methodology for planar loaded antenna arrays is proposed to synthesize a perfect anomalous reflection into an arbitrary direction by optimizing the scattering characteristics of passively loaded array antennas. It is based on efficient and accurate prediction of the induced current distribution and the associated scattering for any given set of load impedances. For a fixed array of finite dimensions, the deflection angles can be continuously adjusted with proper tuning of each load. We study and develop anomalous reflectors as semi-finite (finite $\times$ infinite) and finite planar rectangular arrays comprising printed patches with a subwavelength spacing. Anomalous reflection into an arbitrary desired angle using purely reactive loads is numerically and experimentally validated. Owing to the algebraic nature of load optimization, the design methodology may be applied to the synthesis of large-scale reflectors of practical significance.Comment: 10 pages, 10 figure

An efficient chaotic salp swarm optimization approach based on ensemble algorithm for class imbalance problems

Class imbalance problems have attracted the research community, but a few works have focused on feature selection with imbalanced datasets. To handle class imbalance problems, we developed a novel fitness function for feature selection using the chaotic salp swarm optimization algorithm, an efficient meta-heuristic optimization algorithm that has been successfully used in a wide range of optimization problems. This paper proposes an AdaBoost algorithm with chaotic salp swarm optimization. The most discriminating features are selected using salp swarm optimization, and AdaBoost classifiers are thereafter trained on the features selected. Experiments show the ability of the proposed technique to find the optimal features with performance maximization of AdaBoost

Modeling RIS from Electromagnetic Principles to Communication Systems--Part I: Synthesis and Characterization of a Scalable Anomalous Reflector

This work aims to build connections between the electromagnetic and communication aspects of Reconfigurable Intelligent Surfaces (RIS) by proposing a methodology to combine outputs from electromagnetic RIS design into an RIS-tailored system-level simulator and a ray tracer. In this first part of the contribution, a periodic anomalous reflector is designed using an algebraic array antenna scattering synthesis technique that enables electromagnetically accurate modeling of scattering surfaces with both static and reconfigurable scattering characteristics. The multi-mode periodic structure, capable of scattering into several anomalous angles through manipulation of reactive loads, is then cropped into finite-sized arrays, and the quantization effects of the load reactances on the array scattering are analyzed. An experimental anomalous reflector is demonstrated with a comparison between simulated and measured scattering performance. In the second part, the simulated receiving and transmitting scattering patterns of the anomalous reflector are utilized to build an electromagnetically consistent path loss model of an RIS into a system-level simulator. Large-scale fading is analyzed in simple scenarios of RIS-assisted wireless networks to verify the communication model, and an indoor scenario measurement using the manufactured anomalous reflector sample to support the simulation analysis. After verifying the connections between electromagnetic and communication aspects through simulations and measurements, the proposed communication model can be used for a broad range of RIS designs to perform large-scale system-level and ray-tracing simulations in realistic scenarios.Comment: 10 pages, 7 figure