PIER C | PIER Journals

2026-07-28

PIER C

Vol. 172, 30-37, 2026

doi:10.2528/PIERC26033004

download: 4

A Novel Subarray Division Optimization Algorithm for Sparse Arrays in Microwave Wireless Power Transmission

Jie Wang and Jianxiong Li

To improve beam collection efficiency (BCE) while suppressing sidelobes and limiting implementation complexity in microwave wireless power transmission (MWPT) transmitting arrays with a small number of subarrays, this paper proposes an axially symmetric sparse planar array (SDASPA) model and a one-step subarray-division algorithm named RT-DWCFPSO-SD. The proposed model exploits axial symmetry to reduce search dimension and facilitate a simplified feeding structure. The proposed algorithm jointly optimizes element positions, element excitations, and subarray boundary parameters by combining a constriction factor, dynamic inertia weight, and ring topology. Numerical simulations on an 8 × 8 array with an aperture of 4.5λ × 4.5λ show that, when the array is divided into three subarrays, the proposed method achieves a BCE of 93.42% and a CSL of -13.19 dB. These results indicate that the proposed method is a promising design tool for MWPT transmitting arrays under limited subarray-division conditions.

A Novel Subarray Division Optimization Algorithm for Sparse Arrays in Microwave Wireless Power Transmission

2026-07-28

PIER C

Vol. 172, 18-29, 2026

doi:10.2528/PIERC26042704

download: 10

Performance and Complexity Analysis of Group-Connected Beyond-Diagonal RIS in Multi-User MIMO System

Huda A. Al-Tayyar, Omar M. Ali, Reyam H. Ali and Ali H. Saeed

Reconfigurable Intelligent Surfaces (RIS) have become a trend recently and represent a revolutionary development in wireless communications. Although RIS is utilized to enhance spectrum efficiency, particularly in Multi-User Multi Input Multi Output (MU-MIMO) environments, the conventional diagonal RIS(D-RIS) architecture represents a significant limitation. Beyond-diagonal RIS designs, such as fully-connected (FC-BD-RIS) and group-connected (GC-BD-RIS), are effective in controlling scattering and performance due to their use of reflective RIS elements. This research analyzes in detail the simulation of FC-BD-RIS, GC-BD-RIS, D-RIS and baseline NO-RIS architectures assuming a real communication environment. The results show that the FC-BD-RIS architecture achieves the best performance and highest rate under all operational conditions, while the GC-BD-RIS architecture showed balanced and efficient performance relative to the computational complexity compared to the FC-BD-RIS. Ultimately, the behavior of per-user rate has demonstrated the ability of beyond-diagonal BD-RIS architectures to suppress interference and achieve fairness within MU-MIMO scenarios. Based on the results of this work, GC-BD-RIS is the most practical and suitable for future large-scale 6G applications. This work draws attention to the trade-off among design, optimization, and achievement of RIS-enabled MU-MIMO systems.

Performance and Complexity Analysis of Group-Connected Beyond-Diagonal RIS in Multi-User MIMO System

2026-07-25

PIER C

Vol. 172, 7-17, 2026

doi:10.2528/PIERC26050205

download: 35

A Miniaturized 5.8 GHz WLAN Pentagonal Microstrip Antenna with Fractal DGS and FSS Reflector for Gain Enhancement

Nagari Naveen Kumar and Dupakuntla Vishnu Vardhan

In this article, a Miniaturized Pentagonal Antenna (MPA) with a Minkowski Curve, Fractal Defected Ground Structure (MCF-DGS) and Frequency Selective Surface (FSS) is proposed for 5.725-5.875 GHz WLAN application. The performance of a λ/4 transmission line-fed pentagonal patch antenna is examined using an iterated MCF-DGS etched on the ground plane. In the beginning, a fundamental antenna (Antenna-1) is designed and measured at 13.2 GHz with a S₁₁ of -32.45 dB. After that, the resonant frequency of the fundamental MPA has been reduced from 13.2 GHz to 5.8 GHz by employing MCF-DGS (Antenna-2) with 56% miniaturization. The S₁₁ of MCF-DGS measured for single-band frequency 5.8 GHz is -33.36 dB. The performance attributes of an MPA with improved efficiency, peak directivity, and peak gain via MCF-DGS and FSS (Antenna-3) are also analysed. The proposed antenna of 15 × 16 mm² (or 0.29λ₀ × 0.30λ₀ mm²) with a height of h₁ = 1.6 mm is designed, produced, and tested on a substrate of FR4 epoxy. The peak gain and peak directivity at 5.8 GHz are elevated from 1.74 to 7.40 dBi and 3.53 to 7.95 dBi by using an FSS composed of FR4, with a thickness of h₂ = 1.6 mm, situated under the MPA at a height of h₃ = 8.5 mm. The prototype model's test results are validated by the predicted outcomes of the proposed model.

A Miniaturized 5.8 GHz WLAN Pentagonal Microstrip Antenna with Fractal DGS and FSS Reflector for Gain Enhancement

2026-07-24

PIER C

Vol. 172, 1-6, 2026

doi:10.2528/PIERC26012204

download: 32

Cylindrical Conformal Electrically Small Antenna with Quasi-Isotropic Radiation Pattern for Mine Gob Communication

Qiushou Liu, Kunshan Mo, Jin Wu, Lin Peng and Rui Fang

Wireless communication nodes in the underground mine gob area are often disturbed by different orientations; therefore, antennas with quasi-isotropic radiation are critical for reliable wireless communication. To address this challenge, a compact, cylindrical, conformal, quasi-isotropic antenna operating in the VHF band is proposed. The design integrates a shorted-patch structure with orthogonal dipole radiation, formed by a shorting post and patch aperture, to realize nearly isotropic Radiation. A capacitive-coupling feed is employed to enhance impedance matching, yielding an impedance bandwidth of about 1.02 MHz (S₁₁ < -10 dB) at 170 MHz. The fabricated prototype, with dimensions of 120 mm × 120 mm × 110 mm (0.068λ₀ × 0.068λ₀ × 0.063λ₀), was validated through full-wave simulations and experimental testing. The two results show excellent agreement, demonstrating a measured maximum-minimum gain variation of only 2.74 dB, confirming the antenna's good quasi-isotropic characteristics. Owing to its compact volume, stable matching, and consistent omnidirectional coverage, the proposed antenna is a good candidate for underground mine gob area communication nodes.