PIER M | PIER Journals

2026-08-12

PIER M

Vol. 139, 44-68, 2026

doi:10.2528/PIERM25122403

download: 89

Reconfigurable Intelligent Surfaces Toward 6G: Technologies, Applications, and Open Challenges

Nur Hasni Marzuki, Muzammil Jusoh, Thennarasan Sabapathy, Mohamed Nasrun Osman, Muhammad Ramlee Kamarudin, Samir Salem Al-Bawri and Cihat Seker

Reconfigurable Intelligent Surfaces (RISs) have emerged as a disruptive technology with the potential to fundamentally transform 5G and future 6G wireless communication systems. By intelligently controlling electromagnetic (EM) wave propagation through large arrays of reconfigurable meta-atoms, RIS enables dynamic beam shaping, interference mitigation, coverage enhancement, and energy-efficient communication. This paper presents a comprehensive review of RIS technology, focusing on its fundamental principles, classification, architectural design considerations, and diverse reconfiguration mechanisms. Key aspects, including unit cell structures, material advancements, operating modes, spatial resolution, and control strategies, are examined in detail to provide a holistic understanding of RIS functionality. The review further explores RIS performance modelling, electromagnetic simulation techniques, prototyping methods, and measurement approaches used in evaluating real-world deployments. Emerging application scenarios, including mmWave/THz communications, indoor localization, wireless power transfer, UAV-assisted networks, and smart radio environments, are also highlighted to demonstrate RIS's versatility in next-generation networks. Finally, the paper identifies existing challenges, potential limitations, and future research directions that must be addressed to realize RIS-enabled intelligent wireless ecosystems fully. The insights presented herein aim to guide researchers and industry practitioners in advancing RIS technology as a key enabler for the evolution of future 6G communication systems.

Reconfigurable Intelligent Surfaces Toward 6G: Technologies, Applications, and Open Challenges

2026-08-03

PIER M

Vol. 139, 36-43, 2026

doi:10.2528/PIERM26042801

download: 61

Volume Surface Integral Equation Method with Finite-Gap Lumped-Port Model for EM Radiation by Composite Metallic-Dielectric Structures

Chunying Zhao, Zi-Qiang Wu, Shi-Chao Zeng, Qin-Lei Zhang, Long-Jian Zhou and Qiang-Ming Cai

A novel finite-gap lumped-port model is presented to improve the accuracy of the volume surface integral equation (VSIE) solver for electromagnetic (EM) radiation from composite metallic-dielectric structures. This port model is implemented by modifying the traditional method of moments (MoM) solution to use a novel divergence-conforming testing function at the gap as well as half-basis functions connected across the gap, where a small gap region in the domain of analysis is linked to the lumped-circuit voltage/current source. Then, a hybrid multilevel fast multipole algorithm with multilevel accelerated Cartesian expansion algorithm (MLFMA-MLACEA) is adopted to enhance the capability of this VSIE-based finite-gap lumped-port model for electrically large and multi-scale EM radiation problems. Numerical results are provided to demonstrate the accuracy and efficiency of this VSIE method.

Volume Surface Integral Equation Method with Finite-Gap Lumped-Port Model for EM Radiation by Composite Metallic-Dielectric Structures

2026-07-27

PIER M

Vol. 139, 21-35, 2026

doi:10.2528/PIERM26031803

download: 113

Modulation of Electromagnetic Wave Physical Characteristics by Strongly Anisotropic Acoustic Metamaterials

Zhanying Guo, Hui Li and Yang An

Objective: This study aims to experimentally and numerically investigate the modulation of electromagnetic wave physical characteristics (transmittance, absorptance, impedance) by strongly an isotropic acoustic materialism in the 2-12 GHz frequency band, and to quantify the influence of material parameters (thickness, density, elastic modulus, an isotropic direction) on wave control performance. Methods: Three types of material units (metal composite, polymer, ceramic reinforced) with thicknesses of 1.5-3 mm and anisotropic directions along X, Y, Z axes were fabricated. Transmittance and absorbance were measured using a vector network analyzer with a WR-90 guideway system. Finite element simulations incorporating acoustic-electromagnetic coupling (strain-induced permittivity modulation) were conducted. Sensitivity analysis was performed by varying thickness (±10%), elastic modulus (±5 GPa), density (±500 kg/m³), and direction angle (±15°). Results: High-frequency absorbance reached 0.91 (metal composite at 9.5 GHz), while low-frequency transmittance remained above 0.70. Thickness and elastic modulus predominantly affected the amplitude and position of high-frequency absorption peaks, whereas density and direction angle primarily regulated low-frequency response, resulting in multi-peak broadband absorption. The deviation between experimental data and finite element simulation was less than 3%. Sensitivity analysis revealed that thickness (±10%) and elastic modulus (±5 GPa) produced the most significant changes in transmittance (0.60-0.91) and absorptance (0.70-0.91). Conclusion: Strongly an isotropic acoustic materialism offer mechanically t unable electromagnetic wave control, with thickness and elastic modulus as key design parameters. These findings provide experimental and theoretical references for high-frequency communication antennas, radar stealth coatings, and broadband absorption devices.

Modulation of Electromagnetic Wave Physical Characteristics by Strongly Anisotropic Acoustic Metamaterials

2026-07-20

PIER M

Vol. 139, 11-20, 2026

doi:10.2528/PIERM26050607

download: 120

Using Reverberation Chambers as Test Environments for mmWave Wireless Systems

Alfredo De Leo, Luca Bastianelli, Valter Mariani Primiani, Davide Micheli, Renzo Lattanzi, Pietro Obino, Max Moccia, Thirumaran Muthiah, Riccardo Diamanti and Franco Moglie

This study presents millimeter-wave propagation measurements at 60 GHz conducted in a reverberation chamber to emulate realistic multipath-rich indoor environments. Both line-of-sight (LOS) and non-line-of-sight (NLOS) scenarios are investigated using commercial off-the-shelf devices. The impact of stirring conditions and lossy environments is evaluated through key performance indicators, including Received Signal Strength Indicator (RSSI), Signal-to-Noise Ratio (SNR), Modulation and Coding Scheme (MCS), and throughput. Results show that mechanical stirring speed and the placement of absorbing materials significantly affect channel characteristics and system performance. In NLOS conditions, multipath propagation dominates, where dynamic beamforming demonstrates improved robustness. In contrast, LOS scenarios are highly sensitive to blockage, leading to notable performance degradation. Overall, the findings confirm that the reverberation chamber is an effective platform for over-the-air testing and characterization of 60 GHz wireless systems, offering valuable insights into system behavior under complex indoor propagation conditions relevant to future 5G and 6G deployments.

Using Reverberation Chambers as Test Environments for mmWave Wireless Systems

2026-07-09

PIER M

Vol. 139, 1-10, 2026

doi:10.2528/PIERM26050602

download: 138

A Miniaturized Circularly Polarized Antenna with Embedded Metasurface Patches

Xu Tan, Han Lin, Zhonggen Wang and Wenyan Nie

This study proposes a high-performance miniaturized wideband circularly polarized (CP) metasurface (MTS) antenna for WLAN and 5 GHz wireless communication systems. The design innovatively utilizes a hybrid embedded structure, where regular octagonal patches are incorporated into the gaps of modified X-shaped primary radiating elements to increase edge capacitance and lower resonant frequency, thereby achieving antenna miniaturization. To effectively excite the orthogonal degenerate modes required for CP radiation, a characteristic mode analysis (CMA) was employed to guide the design of the feed network. A feeding structure consisting of a hook-shaped microstrip line and a symmetrical stepped cross-slot is designed to achieve CP excitation via a 90˚ phase delay introduced by path length differences. Measured results demonstrate that the antenna achieves a -10 dB impedance bandwidth of 34.2% (4.38-6.19 GHz) and a 3 dB axial ratio (AR) bandwidth of 23.9% (4.68-5.95 GHz). Regarding radiation characteristics, the radiation efficiency remained stable above 75%, and the peak realized gain reached 5.26 dBic. The experimental results verified that the proposed design achieved stable CP and radiation performance within a miniaturized footprint.