A compact and triple-band polarization converting reflective type metasurface (PCRM) with a high polarization conversion ratio (PCR) is proposed for strategic wireless antenna-integrated applications. The unit cell of the metasurface is composed of S- and G-shaped patches separated with a parasitic gap and the grounded via is connected to the full ground plane. The unit cell is etched on an FR4 substrate (dielectric constant, ε_r = 4.4, loss tangent, tan δ = 0.02), with compact dimensions of 10 mm³ × 10 mm³ × 1.6 mm³. This structure provides a resonance at 5.2 (ISM), 6.9, and 8.05 GHz (X-band) frequencies. The designed unit cell structure is studied for Transverse Electric (TE)/Transverse Magnetic (TM) incident waves and their responses to the various incident angles. The corresponding PCR is calculated, which shows 92% in the lower frequency band (5.2 GHz), 93% in the second frequency band (6.9 GHz), and 94% in the high-frequency band (8.05 GHz). The total efficiency of the structure shows 83.2%, 62.95%, and 64.6% at the respective resonance bands. A prototype of the proposed PCRM with 3 × 3 unit cells is fabricated to validate the simulated results. The experimental data agrees with the simulation results. The compactness, triple-band operation with a high PCR value of more than 92% makes use of the designed metasurface in wireless antenna-integrated applications at ISM and X-bands.

In this paper, a flexible, compact, and semi-transparent monopole antenna integrated with a 2×2 AMC reflector is presented for vehicular communication

В роботі представлено гнучку, компактну, напівпрозору монопольну антену, інтегровану з AMC-рефлектором 2×2, призначену для систем автомобільного зв’язку. Перевернуті F-подібні та L-подібні шлейфи з’єднані з випромінювачем симетрично та наявність щілей у заземленні забезпечують роботу антени в діапазоні 5,85 ГГц. Антена розроблена з використанням гнучкої поліімідної підкладки (ε_r = 3,5, tgδ = 0,025) з розмірами 14×14×0,5 мм³. Елементарна комірка AMC-рефлектора розроблена з використанням підкладки з ПДМС (полідиметилсилоксан) (ε_r = 2,66, tgδ = 0,023) з розмірами 8×8×1 мм³. Коміркова структура AMC-рефлектора складається з резонатора з роздільним кільцем SRR (split ring resonator) і прямокутного кільця з суцільною смужкою заземлення, резонансна частота якого дорівнює 5,85 ГГц. Поверхня 2×2 AMC-рефлектора інтегрована до розробленої антени і знаходиться на відстані 9 мм до неї, що забезпечує приріст коефіцієнту підсилення від 1,73 до 4,56 дБі. Смуга пропускання коефіцієнта відбиття S₁₁ антени з вбудованим AMC-рефлектором становить 0,52 ГГц, тоді як смуга пропускання окремої антени становить 0,44 ГГц. Гнучкість, компактність і отримані показники випромінювання роблять запропоновану структуру антени підходящою для застосування в системах зв’язку в транспортних засобах.

Reconfigurable Intelligent Surfaces (RIS) have become a trending technology with the potential to meet the demand for high data rates and extended signal coverage in mmWave (millimeter wave) and terahertz wireless communications. RIS consists of a planar array of reconfigurable Metasurface unit cells with controllable reflection characteristics to the incident wave. This RIS surface is considered a passive element because it doesn’t consume any power to radiate signal. These RISs offer an energy-efficient alternative to massive MIMO, enabling beamforming, polarization conversion, and beam steering operations. This chapter focused on the fundamentals of RIS, applications to wireless communications, and challenges in RIS design with research directions. A design case study using a numerical simulation tool is presented to understand RIS’s design and analysis. A unique RIS unit cell geometry, utilizing AlGaAs (Aluminium Gallium Arsenide) pin diode is presented in this chapter to get a full insight into the design and simulation methodology. The design and analysis of the RIS unit cell are included, along with simulated results obtained using CST numerical simulation software. A comprehensive analysis of the optimized unit cell and its functionality is demonstrated in this chapter. The design and analysis of a RIS unit cell at mmWave frequencies is the subject of this chapter. In addition to the RIS design aspects, we compare its performance with existing mmWave RIS structures. Finally, the future directions in RIS design are discussed that pave the way to explore the potential of RIS in futuristic 5G/6G communications, such as signal coverage and energy efficiency. Hence, this chapter provides a full insight into fundamentals, an overview of applications, and a design and analysis of the RIS surface to satisfy the enlarged signal coverage and the demand for futuristic wireless communications. <!----> <!----> <!----> <!---->

This paper presents a device sensitive to dielectric material properties, based on a square shaped split-ring resonator (SRR) metasurface operating in the terahertz (THz) frequency band. In the proposed structure, most of the single resonant element is anchored in a silicon substrate, while the remaining part is movable (a magnetic-material-based free-standing cantilever) and can be deformed by an external magnetic field. Owing to its variable geometry, these micro-electro-mechanical systems (MEMS) constitute a reconfigurable resonant element. The structure is designed and analyzed using finite element method (FEM) numerical modeling. The analytical model is presented using an equivalent electrical circuit model. The resonance behavior (at 0.38 THz and 1.13 THz under zero-deflection conditions) is investigated for dispersive, non-dispersive gaseous and liquid material sweep, and a parametric analysis is performed for various deflection levels. This model-based analysis shows that frequency shift of the tunable metasurface sensor, under external material influence and different deflection levels, has potential for sensing (based on detecting changes in the effective permittivity ( ε _eff )) and non-destructive testing applications. This analysis makes the path for future fabrication and experimental validation.