PIER C | PIER Journals

2026-09-24

PIER C

Vol. 173, 357-366, 2026

doi:10.2528/PIERC26082301

download: 48

Multi-Objective Optimization Strategy for Outer-Rotor Permanent Magnet Brushless DC Motors Based on EBF Surrogate Model and GRA-TOPSIS

Xiaoting Ye, Xianhai Yu, Zirui Chen and Tao Zhang

This paper proposes a surrogate model-based multi-objective optimization framework to improve the comprehensive electromagnetic performance of outer rotor permanent magnet brushless DC motors. Targeting key performance metrics including efficiency, torque ripple, cogging torque, core loss and total harmonic distortion (THD) of back-electromotive force (EMF), a parametric finite element model is established to identify key parameters and performance indicators. Dimensionality reduction is carried out through statistical correlation and cluster analysis. An Elliptical Basis Functions (EBF) neural network surrogate model is thereafter constructed to substitute the computationally expensive finite-element model. Different from conventional Response Surface Methodology (RSM) and Radial Basis Function (RBF) models, EBF adopts Mahalanobis distance to mitigate prediction deviation induced by parameter coupling and achieves superior fitting accuracy for strongly-nonlinear motor responses under limited sample size. The Pareto solution set is obtained through the Non-dominated Sorting Genetic Algorithm (NSGA-II). Then, the GRA-TOPSIS multi-criteria decision-making approach is employed to objectively select the global optimal solution from the Pareto solution set and avoid subjective solution selection. Finite element analysis results confirm that the motor performance has been significantly improved: torque ripple, peak cogging torque, core loss, and eddy-current loss are reduced by 18.8%, 18.7%, 6.97%, and 7.12%, respectively, and the effectiveness of constructing an efficient optimization framework has been verified.

Multi-Objective Optimization Strategy for Outer-Rotor Permanent Magnet Brushless DC Motors Based on EBF Surrogate Model and GRA-TOPSIS

2026-09-24

PIER C

Vol. 173, 344-356, 2026

doi:10.2528/PIERC26062202

download: 30

Design and System-Level Analysis of a Row-Column Encoded 1-Bit Reconfigurable Metasurface in Payload-Constrained Aerial Platforms

Rifnaldi, Rifqi Rizqullah, Naufal Radithya Siregar, Suisbiyanto Prasetya, Basith Abdurrohman Asy'ari, Muhammad Zakiyullah Romdlony and Ashif Aminulloh Fathnan

The mitigation of non-line-of-sight (NLoS) blockages in modern multi-user wireless networks increasingly relies on reconfigurable metasurfaces (RMS) for adaptive beamforming. However, achieving high-resolution phase control typically requires complex, heavy biasing networks, which strictly limit deployment on payload-constrained aerial platforms. To address this, this paper presents the design and system-level performance analysis of a low-profile, 1-bit reconfigurable metasurface operating at 5.67 GHz, developed toward eventual integration on Unmanned Aerial Vehicle (UAV) platforms for real-world NLoS mitigation. Designed on a single-layer dielectric substrate, the 10×10 meta-atom array utilizes a row-column addressing architecture that drastically reduces control circuitry to just 20 biasing lines, making it a lightweight and readily fabricable candidate for future UAV-mounted deployment. Adaptive twin-beam steering patterns were synthesized across a ±10^◦ to ±60^◦ design space in which two-tier simulations confirmed reliable beam-pointing accuracy (deviations below 1.5^◦) for target angles up to ±40^◦, while revealing significant pointing degradation at ±50^◦ and beyond due to element-pattern roll-off. To assess its potential for payload-constrained applications, the metasurface operation as a UAV-mounted relay was evaluated through a simulated NLoS communication scenario within this validated ±40^◦ range. The system exhibits strong spatial selectivity, effectively isolating targeted users from interference and demonstrating its capability to restore blocked data links under simulated deployment conditions. By delivering a decisive 8 to 14 dB Signal-to-Noise Ratio (SNR) advantage to maintain a stringent 10^-3 Bit Error Rate (BER), this work establishes the hardware-efficient metasurface as a promising, deployment-ready design for future resilient aerial communication systems, with physical prototyping and real-world flight testing planned as the next stage of this research.

Design and System-Level Analysis of a Row-Column Encoded 1-Bit Reconfigurable Metasurface in Payload-Constrained Aerial Platforms

2026-09-22

PIER C

Vol. 173, 331-343, 2026

doi:10.2528/PIERC26071302

download: 95

Compact Frequency-Reconfigurable Diamond-Slotted Antenna for Wideband 5G/6G and IoT Applications

Salah Eddine El Aoud, Hind Abbaoui, Nasima El Assri, Saïda Ibnyaich, Abdelouhab Zeroual, Mohd Muzafar Ismail, Sharman Sundarajoo and Ahmed Jamal Abdullah Al-Gburi

This paper introduces an ultra-miniaturized, reconfigurable antenna for wireless communication applications. The suggested reconfigurable antenna is fabricated on an FR4-epoxy substrate (20 × 20 × 1.6 mm³, ε!= 4.4), and it provides a miniature factor 79% which is an outstanding value. Frequency reconfiguration can be achieved using two PIN diodes, which make the proposed antenna capable of working in various frequencies, including 5G/6G, WLAN, HiperLAN, V2X, WiMAX, Wi-Fi 6E/7/8, and S/C/X/Ku bands. With the analysis performed by CST Studio Suite, the proposed antenna shows outstanding quantitative results without any sacrifice in its size, cost, or complexity. In this context, the antenna shows dual-band impedance bandwidths of 1.36 GHz and 6.4 GHz. Additionally, it has 2 dBi of peak gain and 79% high radiation efficiency.

Compact Frequency-Reconfigurable Diamond-Slotted Antenna for Wideband 5G/6G and IoT Applications

2026-09-21

PIER C

Vol. 173, 321-330, 2026

doi:10.2528/PIERC26080901

download: 43

A Concentric Multi-Ring Circular Monopole Antenna Designed by Characteristic Mode Analysis for Continuous Sub-6 GHz 5G Coverage

Immanuel Prabaharan Soundararajan, Muthurajan Subramoniam, Arul Kulandaivel, Lakshmi Dhandapani and Rajeshkumar Dhandapani

This paper presents a single-port concentric multi-ring circular monopole in which each ring is a separate characteristic-mode resonator, and cross spokes force the ring currents in phase so that the individual ring resonances merge into one continuous impedance band. This ring-per-mode partitioning distinguishes the design from single-mode monopoles, and characteristic mode analysis (CMA) is used to place and order the modes rather than explain a finished geometry. The radiator occupies 0.27λ₀ × 0.39λ₀ on a 33 × 23 × 0.8 mm³ RT/Duroid 5880 substrate (ε_r = 2.2, tan δ = 0.0009), a low-permittivity laminate that resists miniaturisation. A central disc of radius 5.5 mm and three concentric rings of mean radii 6.27, 7.79, and 10.14 mm are excited by a 50 Ω microstrip line whose 2.465 mm width follows directly from Hammerstad synthesis, and a triangular tapered partial ground of height 10.66 mm - one quarter-wavelength at band centre completes the match. Closed-form ring resonances of 3.72, 4.84 and 6.02 GHz agree with the modal spectrum and with the measured lower resonance at 3.65 GHz to within 1.9%. The measured impedance band spans 3.50-6.15 GHz, a fractional bandwidth of 54.9% centered at 4.83 GHz, and covers the 5G NR n77, n78 and n79 bands together with the 5.5 GHz WLAN band in one continuous match. A physically partitioned equivalent circuit, one series-RLC branch per ring with every branch resonance fixed to its closed-form value, reproduces the full-wave reflection response with a 0.72 dB RMS error. The design gives a compact, single-layer, single-feed route to full sub-6 GHz coverage with an analysis chain that ties every dimension to a resonant mechanism.

A Concentric Multi-Ring Circular Monopole Antenna Designed by Characteristic Mode Analysis for Continuous Sub-6 GHz 5G Coverage

2026-09-20

PIER C

Vol. 173, 308-320, 2026

doi:10.2528/PIERC26072802

download: 59

Design of a Dual-Band Quad-Element MIMO Antenna with Wideband Characteristics for 5G Sub-6 GHz and U6G Applications

Chengzhu Du, Yuhao Wu and Ziyi Zhou

This paper proposes and investigates a dual-band four-element MIMO antenna structure. The antenna operates across several frequency bands, including U6G, 5G n256, 4G LTE, WiMAX, and WLAN 5G, while maintaining its intended functionality. The proposed CPW-fed antenna adopts slot radiators and occupies a compact volume of 103.72 × 103.72 × 0.8 mm³. A trident-shaped branch enhances bandwidth, and the antenna's dual-band performance comes from etching a semi-elliptical ring slot. Experimental results show that the antenna provides two impedance bandwidths of 2200 MHz (1.81-4.01 GHz) and 2380 MHz (4.85-7.23 GHz). These bandwidths fully cover the required operating ranges, including WLAN 5G (5.15-5.35 GHz and 5.725-5.825 GHz), U6G (6.425-7.125 GHz), 5G n256 (1.98-2.01 GHz and 2.17-2.2 GHz), 4G LTE (2.3-2.39 GHz and 2.555-2.655 GHz) and WiMAX (3.3-3.8 GHz). Furthermore, the proposed antenna achieves a peak gain of 4.08 dB at 2.5 GHz and 6.42 dB at 6 GHz. The ECC remains less than 0.003, and the DG exceeds 9.99, indicating superior diversity performance. These findings indicate that the proposed dual-band four-element MIMO antenna is highly suitable for use in 5G sub-6 GHz and U6G communication systems.

Design of a Dual-Band Quad-Element MIMO Antenna with Wideband Characteristics for 5G Sub-6 GHz and U6G Applications

2026-09-20

PIER C

Vol. 173, 299-307, 2026

doi:10.2528/PIERC26072201

download: 50

Vibration Analysis and Optimization of Flux Reversal PM Machine with PM Chamfer

Bo Tian, Qiang Shi, Jianyi Yang, Guofeng Diao, Mingxin Luo and Libing Jing

Flux reversal permanent magnet machine (FRPMM), owing to their high power density and excellent low-speed high-torque capability, is considered promising for low-speed direct-drive hydropower generation systems. However, the vibration and noise caused by radial electromagnetic force hinder the development of the FRPMM. A novel FRPMM with a permanent magnet (PM) chamfer on the stator is proposed. First, the radial force density, average torque, and torque ripple are taken as optimization objectives. The multi-objective genetic algorithm (MOGA) is used to optimize the machine. Next, the space-time characteristics of air-gap flux density and radial force density are obtained based on finite-element simulation. The modal analysis and harmonic response analysis of the stator are carried out. The results show that the radial force density of the proposed FRPMM is significantly reduced, and the machine's vibration characteristics are optimized.

Vibration Analysis and Optimization of Flux Reversal PM Machine with PM Chamfer

2026-09-19

PIER C

Vol. 173, 293-298, 2026

doi:10.2528/PIERC26062201

download: 50

Power Divider Based on Broadside-Coupled Coplanar Waveguides

Young Kim

This paper presents power divider that combines broadside coupling and coplanar waveguides. This structure enables the tuning of the coupling coefficient by changing the microstrip line width on the top and bottom surfaces as well as the slot spacing between the line and the ground plane. This developed power divider can be easily fabricated with a single-layer structure, without requiring complex multilayer manufacturing of a printed circuit board. To verify the effectiveness of this proposed structure, simulation and measurement were performed at a center frequency of 2 GHz. The measurement results of the implemented power divider agreed well with the simulation results.

Power Divider Based on Broadside-Coupled Coplanar Waveguides

2026-09-18

PIER C

Vol. 173, 279-292, 2026

doi:10.2528/PIERC26042406

download: 86

A Compact PIN Diode-Based Independently Fed Frequency and Pattern Reconfigurable Hybrid Antenna Array for Wireless Applications

Yogesh Shankar Ghodake and Shankar D. Nawale

This paper proposes a compact, independently fed hybrid antenna array featuring reconfigurable frequency and radiation patterns for adaptive wireless applications, employing PIN diodes. The hybrid arrangement incorporates independently driven elements with diode-controlled current pathways to enable concurrent spectral and spatial tuning within a single structure. Frequency agility is achieved through PIN-diode switching configurations; five representative states are presented, due to the similarity among the other responses, with resonant frequencies derived from the minima of the S-parameters. Multiband operation is demonstrated in simulation from 3.8 to 6.49 GHz and in measurement from 4.18 to 6.56 GHz; the mutual coupling suppression is achieved by an independently fed architecture, maintaining inter-port isolation better than 18-20 dB throughout the operating band, which signifies effective suppression of mutual coupling within the operating band. Radiation pattern reconfigurability is achieved via PIN diode switching, yielding directional radiation-pattern reconfigurability through electronic switching via controlled redistribution of surface current. The design remains compact at 40 × 44 mm² and uses only four PIN diodes, reducing switching complexity while preserving stable gain and radiation performance. Measured results show good agreement with simulations, validating the design's effectiveness. The proposed antenna provides a compact and low-complexity solution for adaptive sub-6 GHz wireless communication systems requiring simultaneous frequency and radiation-pattern reconfigurability.

A Compact PIN diode-based Independently Fed Frequency and Pattern Reconfigurable Hybrid Antenna Array for Wireless Applications

2026-09-17

PIER C

Vol. 173, 266-278, 2026

doi:10.2528/PIERC26062901

download: 101

Design and Experimental Characterization of a Compact Quad-Port UWB-MIMO Antenna with Dual-Band Notches

Sunitha Mandava, Thotakura Sushma, Rajesh Gogineni, Chunduri Kiran Kumar, Ramesh Babu Sadineni and Veeravalli Ramakoteswara Rao

This paper presents a compact 39 × 39 mm² quad-port ultra-wideband (UWB) MIMO antenna with dual band-notches and enhanced inter-element isolation. Four orthogonally arranged microstrip-fed circular radiators are employed to reduce mutual coupling, while two U-shaped slots etched on each radiator suppress interference from the C-band (3.1-4.3 GHz) and Wireless LAN (5.2-5.6 GHz) bands. We investigate the antenna using Characteristic Mode Analysis through modal significance and modal current distributions. The proposed diversity antenna is evaluated using envelope correlation coefficient, diversity gain, total active reflection coefficient, channel capacity loss, multiplexing efficiency, and simulated group delay. The antenna achieves an impedance spectrum covering 2.9-10.6 GHz, radiation efficiency of 90%, gain of 5.2 dBi, ECC < 0.02, and isolation of -20 dB. The results demonstrate that the proposed antenna provides an effective combination of small size and high isolation, making it viable for UWB applications.

Design and Experimental Characterization of a Compact Quad-Port UWB-MIMO Antenna with Dual-Band Notches

2026-09-13

PIER C

Vol. 173, 256-265, 2026

doi:10.2528/PIERC26073001

download: 118

Improved Terminal Sliding Mode Control for PMSM Dual-Inertia System Based on Dual Finite-Time Disturbance Observers

Jinyang Zou, Kaihui Zhao, Gang Fan, Kai Shen and Lin Jia

To address speed-tracking degradation and torsional vibration caused by flexible-shaft coupling and load disturbances in PMSM dual-inertia systems, this paper proposes a high-order nonsingular fast integral terminal sliding mode control (HONFITSMC) method integrated with dual finite-time extended sliding mode disturbance observers (FTESMDOs). First, a third-order load-side dynamic model is derived to explicitly describe the effects of shaft torque and load disturbance. Next, the HONFITSMC method is developed using an inner integral sliding surface, an outer high-order sliding surface, and a dual-power reaching law. Furthermore, a weighting function is introduced to adapt the convergence speed across different error regions, reducing chattering and improving speed-tracking accuracy. Then, dual FTESMDOs are designed for the motor side and load side to estimate the shaft torque and load-side disturbances, and the estimated values are fed forward into the control law for real-time compensation. The simulated and experimental results demonstrate that the proposed control scheme significantly improves the system's disturbance rejection capability and overall robustness.

Improved Terminal Sliding Mode Control for PMSM Dual-Inertia System Based on Dual Finite-Time Disturbance Observers

2026-09-13

PIER C

Vol. 173, 243-255, 2026

doi:10.2528/PIERC26070702

download: 98

Multi-Objective Optimization Design of Water-Filled Submersible Permanent Magnet Synchronous Motors Incorporating Rotor Water Friction Loss

Sili Zhou, Shuo Zhou, Tianxiang Zhu, Zhonggen Wang, Yuanyuan Jiang and Qunjing Wang

Rotor water friction loss is a critical determinant of the overall performance and efficiency of water-filled submersible permanent magnet synchronous motors (WSPMSMs) employed in mining applications. This study analyzes the electromagnetic performance and rotor water friction loss of a 500\,kW WSPMSM using the finite element method and computational fluid dynamics (CFD), respectively. From a structural optimization perspective, the effects of the air-gap length and stator slot shape on rotor water friction loss were examined. A multi-objective optimization method incorporating rotor water friction loss was proposed, featuring variable stratification and differentiated reduction of optimization ranges. Firstly, an orthogonal array was constructed using the Taguchi method, and both electromagnetic finite element and CFD simulations were performed. Secondly, analysis of variance (ANOVA) classified design variables as significant and insignificant. Based on the multiple performance characteristic index (MPCI) analysis, the optimization ranges of two types of variables were narrowed to different extents. Finally, for significant variables, the response surface method (RSM) coupled with the non-dominated sorting genetic algorithm III (NSGA-III) was applied for precise optimization. For insignificant variables, the Taguchi method or parameter scanning was used for rapid optimization, depending on their number. By comparing the optimization results of the proposed method with those of existing methods, the effectiveness and superiority of the proposed method were verified.

Multi-Objective Optimization Design of Water-Filled Submersible Permanent Magnet Synchronous Motors Incorporating Rotor Water Friction Loss

2026-09-13

PIER C

Vol. 173, 230-242, 2026

doi:10.2528/PIERC26080603

download: 82

Graphene-Based Multi-Band Reconfigurable Terahertz Antenna with Wide Tuning Range

Khalid Subhi Ahmad, Muhammad Inam Abbasi, Ahmed Jamal Abdullah Al-Gburi and Mohamad Zoinol Abidin Abd Aziz

This work demonstrates the design of a terahertz (THz) antenna that utilizes graphene to achieve frequency-reconfigurable multiband operation. The proposed design integrates electrically controlled graphene switches within precisely defined slots to dynamically modify the distribution of surface currents, enabling a highly multi-band, frequency-reconfigurable antenna. The antenna consists of perpendicular (vertical and horizontal) slots, supported by six graphene switches, whose operating frequencies are adjusted by controlling the graphene's chemical potential. The proposed antenna covers a wide frequency range from 0.288 to 2.501 THz, operating at 63 resonant frequencies and 58 impedance bands, achieved through 11 reconfiguration states (C1-C11). The proposed antenna is created on a 10 μm-thick Rogers RO3003 substrate with overall dimensions of 268 μm × 240 μm × 10 μm. The performance of the proposed antenna, including the reflection coefficient, gain, and radiation efficiency, was evaluated under different operating conditions. Due to its ability to reconfigure multiple frequency bands, this antenna is an ideal solution for dynamically adjustable, tunable THz communication systems.

Graphene-Based Multi-Band Reconfigurable Terahertz Antenna with Wide Tuning Range

2026-09-13

PIER C

Vol. 173, 215-229, 2026

doi:10.2528/PIERC26061802

download: 88

CMA-Based Design of a Wideband RHCP Antenna with Gain and Bandwidth Enhancement Using Parasitic Element

Sagar Babanrao Pokharkar and Kanchan Tiwari

Existing wideband circularly polarized (CP) antennas generally face trade-offs among wide impedance bandwidth, broad axial ratio (AXR) bandwidth, gain, and compactness in single-layer implementation. Furthermore, a number of reported designs are multi-layer or metasurface-based or require complex feeding networks, making them more complex to manufacture, resulting in increased fabrication costs. In this paper, we develop a wideband circularly polarized (CP) antenna design using an active central patch with four parasitic patches on an FR4 substrate. The CP condition is obtained by exciting two orthogonal modes of equal magnitude and $90^\circ$ phase difference, which are attained by perturbing the active patch and placing a diagonal coaxial feed on it. We enhance the broadside gain and bandwidth by loading parasitic patches around the active patch via electromagnetic coupling. This type of coupling improves aperture efficiency, impedance matching, and axial ratio bandwidth (ARBW). Characteristic Mode Analysis (CMA) is used to determine and optimize the dominant orthogonal modes responsible for circular polarization and radiation enhancement. The fabricated prototype shows a measured -10 dB impedance bandwidth (IBW) of 18.12% (5.42-6.50 GHz), an ARBW of 17.87% (5.35-6.40 GHz), and a broadside gain of 8.5 dBi. The measured and simulated results show excellent agreement, confirming the functionality of the designed antenna. The antenna's compact size, wide bandwidth, and high broadside gain make it a potential solution for broadband wireless communication, satellite-based systems, and C-band antenna applications.

CMA-Based Design of a Wideband RHCP Antenna with Gain and Bandwidth Enhancement Using Parasitic Element

2026-09-11

PIER C

Vol. 173, 207-214, 2026

doi:10.2528/PIERC26071407

download: 83

A Compact Multilayer Quad-Band Bandpass Filter with Coupled SIRs for Multi-Standard Wireless Systems

Hassan Saad Abdullah and Raaed Thaaban Hammed

In this paper, we propose a compact quad-band bandpass filter by using short-ended stepped-impedance resonators (SE-SIRs) and open-ended stepped-impedance resonators (OE-SIRs) in a hybrid structure. The proposed design uses the odd- and even-mode resonances of the two types of resonators to produce four independent passbands in a compact multilayer structure. The first and second passbands are set by SE-SIR resonators at 1.56 and 2.5\,GHz, respectively. The third and fourth passbands are centered at 3.5 and 5.2\,GHz, respectively, due to the OE-SIR resonators. To achieve the quad-band response in a compact size, a multilayer arrangement with electromagnetic broadside coupling between the feeding structure and resonators has been adopted. Finally, the filter is designed, simulated, fabricated, and measured using a Rogers-Ceramic RO4360 substrate with a permittivity of ε_r = 6.15 and thicknesses of (h₁ = 0.3, h₂ = 0.508) mm. Simulated insertion losses were 0.29, 0.26, 0.43, and 0.66 dB, and return losses were 28.65, 15.05, 14.04, and 17.3 dB in each of the four operating bands, respectively. Filter responses from simulation and measurement are contrasted and discussed. The produced filter is very small, covering a circuit area of about 129 mm², without feeding ports.

A Compact Multilayer Quad-Band Bandpass Filter with Coupled SIRs for Multi-Standard Wireless Systems

2026-09-10

PIER C

Vol. 173, 198-206, 2026

doi:10.2528/PIERC26071002

download: 104

Compact Dual-Band Multiport Antenna Array with Integrated Beam-Switching and Polarization Diversity for Next-Generation WLAN Access Points

Ridha Omrani and Halim Boutayeb

This paper presents the design, numerical modeling, and experimental validation of a compact, collocated multi-port reconfigurable antenna array optimized for high-density WLAN access points. The proposed structure supports robust dual-band operation covering the 2.4-2.5 GHz and 5.2-5.8 GHz frequency ranges, exhibiting a measured reflection coefficient well below -10 dB across both bands. Polarization diversity is successfully achieved through orthogonally oriented, horizontally and vertically polarized radiation elements, ensuring an isolation higher than 17 dB between adjacent ports. Furthermore, an integrated electronic switching network based on PIN diodes enables flexible radiation pattern control, allowing seamless switching between a 360° omnidirectional coverage mode and multiple directive beam states. The omnidirectional configuration provides a stable baseline for wide-area connectivity, while the directive modes focus electromagnetic energy into specific spatial sectors, boosting the peak total gain from 5.16 dBi to 7.14 dBi. This dynamic beam-steering capability significantly mitigates multi-path fading and optimizes Multiple-Input Multiple-Output (MIMO) system performance in complex indoor environments. The entire array architecture occupies a compact physical footprint of only 200 mm × 200 mm, with excellent agreement between simulated and measured results, confirming its suitability for next-generation WLAN infrastructure.

Compact Dual-Band Multiport Antenna Array with Integrated Beam-Switching and Polarization Diversity for Next-Generation WLAN Access Points

2026-09-08

PIER C

Vol. 173, 190-197, 2026

doi:10.2528/PIERC26072002

download: 168

Krylov Subspace Acceleration by Adaptive Cross Approximation for Improved CBFM Electromagnetic Scattering Computation

Xiaofei Ma, Zhonggen Wang, Wenyan Nie and Han Lin

To resolve the trade-off between numerical accuracy and computational efficiency when integrating the adaptive cross approximation (ACA) into the characteristic basis function method (CBFM), this paper proposes a hybrid optimization framework incorporated with Krylov subspaces. This framework first employs CBFM to partition scattering targets into multiple subdomains and realize dimension reduction of the impedance matrix. It then adopts the ACA algorithm to perform low-rank compression on far-field coupling submatrices. On this basis, the GMRES algorithm is introduced to implement iterative optimization. The framework uses the approximate solution from CBFM as the initial iterative guess, and it leverages ACA to accelerate constructing Krylov subspaces for reducing iterative computational overhead. Numerical results of two sets of test cases demonstrate that, compared with the traditional coupled CBFM-ACA solver, the proposed method can significantly improve numerical accuracy while maintaining favorable computational efficiency.

Krylov Subspace Acceleration by Adaptive Cross Approximation for Improved CBFM Electromagnetic Scattering Computation

2026-09-08

PIER C

Vol. 173, 180-189, 2026

doi:10.2528/PIERC26062602

download: 103

A Four-Port Wideband MIMO Antenna with Tapered Feedline and U-Shaped Slots for Dual-Band Rejection and Circular Polarization

Pandillapalli Janardhana Reddy and Gummadi Kameswari

This work presents a compact four-port low-profile multi-input multi-output(MIMO) antenna designed for wideband wireless communication over the S(2-4 GHz), C(4-8 GHz), and lower X-band(8-12 GHz) spectrum. The proposed antenna initially exhibits a broad impedance bandwidth extending from 2.5 to 9 GHz under the standard -10 dB matching condition. To improve spectral selectivity and mitigate unwanted interference, U-shaped slots are embedded in the feeding line and radiator, generating two distinct rejection bands at 3.5-3.9 GHz and 5.1-5.9 GHz, corresponding to WiMAX and WLAN frequencies, respectively. Including these slots slightly shifts the upper operating limit to 8.5 GHz. Implemented on an FR4 dielectric substrate (ε_r = 4.4) with a thickness of 1.6 mm, the antenna occupies an overall footprint of 40 × 34 mm². Additionally, circular polarization is achieved across the 6.1-7.9 GHz region, enhancing communication reliability in multipath propagation environments. A common-ground decoupling structure is employed to improve port isolation and suppress mutual coupling, resulting in isolation greater than 20 dB. The antenna demonstrates favorable diversity characteristics, with an envelope correlation coefficient below 0.05 and a diversity gain exceeding 9.95 dB. Moreover, a maximum realized gain of 6.2 dBi is obtained within the operational band. Experimental validation of the fabricated prototype confirms close agreement with simulated results, highlighting its potential for compact wideband multi-antenna wireless systems.

A Four-Port Wideband MIMO Antenna with Tapered Feedline and U-Shaped Slots for Dual-Band Rejection and Circular Polarization

2026-09-06

PIER C

Vol. 173, 167-179, 2026

doi:10.2528/PIERC26070101

download: 129

A Compact Fibonacci Fractal MIMO Antenna with Slotted Decoupling Structure for 5G and WLAN Applications

Sachin S. Khade, Nikhil Mangrulkar, Praful N. Yerkewar, Tirupati M. Goskula, Chitra S. Khade and Prajwal Rewatkar

A miniaturized, multiband, Fibonacci-inspired MIMO antenna is proposed for modern wireless communication technologies, such as sub-6 GHz 5G, WiMAX, WLAN, and Wi-Fi. The proposed antenna incorporates a Fibonacci spiral as the radiating element along with an enhanced defected ground structure (DGS). This configuration provides improved impedance matching, low mutual coupling, and strong diversity characteristics. The antenna employs a slot-loaded decoupling strip and an optimized ground plane to suppress surface currents and enhance isolation between elements. In its final two-element configuration, the antenna exhibits three distinct resonant frequencies at 1.1 GHz, 4.22 GHz, and 5.65 GHz. Both simulated and measured results demonstrate excellent impedance matching, achieving a minimum return loss of -27.22 dB at 4.22 GHz and an isolation level better than -20 dB throughout the operating frequency range. Moreover, the envelope correlation coefficient (ECC) remains below 0.05, while the diversity gain exceeds 9.95 dB. The antenna also achieves a radiation efficiency ranging from 75% to 85%. Surface current analysis further demonstrates that the combination of the Fibonacci-inspired geometry and DGS effectively produces multiband operation while minimizing mutual coupling.

A Compact Fibonacci Fractal MIMO Antenna with Slotted Decoupling Structure for 5G and WLAN Applications

2026-09-05

PIER C

Vol. 173, 158-166, 2026

doi:10.2528/PIERC26070402

download: 228

A Long-Range Flexible UHF RFID Tag Antenna with Robust Horizontal Readability

Jie Wu, Wei Huang, Lei Ren and Jiade Yuan

A compact, flexible, ultra-high-frequency (UHF) radio-frequency identification (RFID) tag antenna is proposed for the long-range identification of non-metallic logistics objects with robust horizontal readability. The antenna consists of an open-frame meandered radiator, an upper transverse coupling path, a central interdigital coupling section, and a lower comb-shaped multi-branch section. Together, these coupled sections extend the effective current path, improve antenna-chip power transfer, and establish a distributed current response over the antenna. The fabricated tag measures 40 mm × 29.5 mm × 0.05 mm. Under an effective isotropic radiated power of 3.28 W, the maximum measured read range is 16.6 m at 919 MHz in free space, with a 0°-360° xoy-plane read range of 15.2-16.6 m. Attachment tolerance is evaluated on PP plastic, folded denim, cardboard, and wood, yielding maximum read ranges of 16.7, 13.2, 11.4, and 11.2 m, respectively. Across all five cases, the horizontal stability coefficient C_s = R_min/R_max is at least 0.895. The proposed coupled multi-section topology provides a distributed-current strategy for simultaneously improving angular readability and attachment robustness in flexible UHF RFID tags.

A Long-Range Flexible UHF RFID Tag Antenna with Robust Horizontal Readability

2026-09-05

PIER C

Vol. 173, 152-157, 2026

doi:10.2528/PIERC26050301

download: 89

Dielectric and Anomalous Dispersion Behavior of Conductive Polyaniline Carbon Nanotube Composite at X-Band Frequencies

Puthanpurakkal Sasikumar Sreekala and Selvaraj Gokul

This paper provides a detailed discussion of anomalous dispersion studies of polyaniline carbon nanotube composites (PANI-CNT) in the X-band frequency range. Dielectric properties are used to demonstrate the material's anomalous behavior. Measurement analysis is performed using a network analyzer; the anomalous medium shows a phase advance, while the other shows a gradual phase decrease. By correlating these characteristics, we can observe their significant impact on the material's microwave properties. We present PANI-CNT powder throughout the study. PANI-CNT exhibits enormous microwave enhancement characteristics compared to standard materials. This paper examines various microwave parameters, including permittivity and shielding efficiency. The novelty of the anomalous effect lies in the significant enhancement of shielding efficiency it produces.

Dielectric and Anomalous Dispersion Behavior of Conductive Polyaniline Carbon Nanotube Composite at X-band Frequencies

2026-09-04

PIER C

Vol. 173, 142-151, 2026

doi:10.2528/PIERC26051601

download: 171

Impact of Magnetic Saturation on Back-EMF in PMSMs Using a Hybrid Analytical Approach

Samir Mezghiche, Brahim Ladghem-Chikouche, Lazhar Roubache and Zakarya Djelloul-Khedda

Fast, accurate modeling of permanent magnet synchronous machines (PMSMs) is essential for efficient design optimization, particularly in high-power wind turbine applications where severe magnetic saturation frequently occurs. While pure analytical models offer rapid computation, they often fail to accurately account for nonlinear saturation, which significantly affects the machine's performance, particularly the back-electromotive force (back-EMF). This study proposes a computationally efficient 2D hybrid analytical framework to investigate the impact of magnetic saturation on the back-EMF in PMSMs. The proposed approach couples an exact analytical subdomain (SD) technique, which is used to resolve the magnetic field in linear regions, with a nonlinear magnetic equivalent circuit (MEC) model for the active ferromagnetic parts. By iteratively updating the relative permeability in the MEC, the method accurately captured local saturation effects and reflected them in the global air-gap flux density. The developed hybrid analytical model (HAM) was used to analyze the total harmonic distortion (THD) and peak values of the back-EMF under saturated conditions. To validate the proposed method, results were compared with those obtained from a 2D finite element analysis (FEA). The comparison shows that the hybrid approach achieves an excellent compromise, delivering a high accuracy comparable to that of the FEA while drastically reducing computational time, making it highly suitable for iterative design and optimization process.

Impact of Magnetic Saturation on Back-EMF in PMSMs Using a Hybrid Analytical Approach

2026-09-04

PIER C

Vol. 173, 134-141, 2026

doi:10.2528/PIERC26060801

download: 100

Enhancing Reliability in 6G IoT Networks through Full-Duplex Decode-and-Forward Relaying with Maximum Ratio Transmission

Awfa Aladwani and Tansal Gucluoglu

Compared with widely used half-duplex relaying, the development of full-duplex (FD) relaying devices enables simultaneous transmission and reception, which can be desirable for spectrally efficient 6G Internet of Things (IoT) networks. To improve the reliability of FD relaying, maximum ratio transmission (MRT) can be incorporated into an FD decode-and-forward (DF) relaying architecture, making the resulting scheme practical for diverse applications. In this study, critical performance metrics, such as the outage probability, symbol error rate and channel capacity were derived for the Nakagami-m fading channel model. Numerical examples obtained via Monte Carlo simulations corroborate the theoretical expressions and demonstrate that MRT can efficiently mitigate residual self-interference while preserving low receiver complexity. These findings provide useful insights for system designers to consider FD-DF relaying with MRT as a practical and effective solution for next-generation wireless ecosystems.

Enhancing Reliability in 6G IoT Networks through Full-Duplex Decode-and-Forward Relaying with Maximum Ratio Transmission

2026-09-04

PIER C

Vol. 173, 121-133, 2026

doi:10.2528/PIERC26070803

download: 224

A Dual-Port UWB MIMO Antenna with Triple Notch Characteristics Based on CPW Feeding

Jiasheng Li, Han Lin, Wenyan Nie and Zhonggen Wang

This paper proposes a dual-port Ultra-Wideband (UWB) Multiple-Input Multiple-Output (MIMO) antenna with triple notch characteristics based on Coplanar Waveguide (CPW) feeding. The antenna achieves triple notch performance by introducing two L-shaped and one inverted U-shaped electromagnetic band gap (EBG) structures on the back of the substrate and etching inverted U-shaped grooves on the feed line, thereby suppressing interference from WiMAX, WLAN, and the C-band. The simulation and experimental results show good agreement, verifying the feasibility of the proposed antenna. The results show that this antenna covers the entire UWB band from 3.08 to 10.87 GHz, with a reflection coefficient of less than -10 dB, mutual coupling coefficient of less than -20 dB, envelope correlation coefficient (ECC) of less than 0.0072, and diversity gain (DG) exceeding 9.9997 dB within the operating band. It meets the requirements of high-performance MIMO systems for channel independence and transmission efficiency, and has potential applications in modern UWB communication systems.

A Dual-Port UWB MIMO Antenna with Triple Notch Characteristics Based on CPW Feeding

2026-09-03

PIER C

Vol. 173, 116-120, 2026

doi:10.2528/PIERC26072103

download: 78

Analysis of Impact on BTM Antenna by Trackside Electromagnetic Environment in Integration of Multi-Network

Meng Li

Large metropolitan areas have planned different types of rail transit integrating into transportation hubs due to the needs of integrated development. Owing to scenarios such as parallel or cross-line operation of a junction station, a complex electromagnetic environment may affect the normal operation of BTM equipment. Therefore, it is necessary to study the influence of the trackside electromagnetic environment on the BTM antenna. Taking the scenario in which the parallel section of a mainline railway and an urban rail transit enters the station, as well as the situation in which two trains are adjacent at the junction station, as an example, the model of the BTM antenna is established to analyze the electromagnetic interference of urban rail transit trains in operation. The induced voltage of the BTM antenna in urban rail transit trains is calculated based on electromagnetic environment data from the electromagnetic disturbance source collected on site to analyze the influence on its normal operation. The amplitude of the induced voltage at the BTM antenna port is lower than its normal operation scenario when the parallel section of a mainline railway and an urban rail transit enters the catenary hard across section. The amplitude satisfies the requirement of its starting electromagnetic environment when the urban rail train stops at the platform while the mainline train passes at speed. Under a multi-network integration background, research results show that the trackside electromagnetic environment along the mainline railway will not cause an electromagnetic interference problem for the BTM antenna of the urban rail train.

Analysis of Impact on BTM Antenna by Trackside Electromagnetic Environment in Integration of Multi-Network

2026-09-02

PIER C

Vol. 173, 103-115, 2026

doi:10.2528/PIERC26051202

download: 140

Bistatic Radar for Multi-Target Detection Using Microstrip Patch Antennas

Ankita Malhotra, Priyal Veera, Aryan Bhalkar, Rajiv Datta, Shubham Tayade and Amit A. Deshmukh

This paper presents a compact, low-cost, frequency-domain bistatic radar system using two identical square microstrip patch antennas fabricated on an FR-4 substrate (εr = 4.4, thickness = 1.6 mm). The antenna incorporates a suspended air-gap configuration to enhance bandwidth and radiation efficiency, and is designed to resonate near 3.3 GHz. The antenna was designed and optimised using CST Microwave Studio and experimentally validated using a Vector Network Analyser (VNA). Simulation results demonstrate a peak gain of 6.6 dBi and radiation efficiency of 83.2%. The fabricated antenna exhibits a measured peak gain of 7.0 dBi at 3.23 GHz and a |S₁₁| ≤ −10 dB bandwidth from approximately 3.0 to 3.5 GHz, with a measured resonance minimum of −14.3 dB at 3.27 GHz. The bistatic radar system operates over a swept frequency range of 2.8 to 3.8 GHz, acquiring complex S₂₁ parameters at each discrete frequency step. The received S₂₁ data is processed using background subtraction to suppress antenna coupling and background clutter, followed by an Inverse Fast Fourier Transform (IFFT) for range-domain target localisation. The proposed system is experimentally validated in single-target and multiple-target scenarios. Closely spaced targets are further characterised using a CLEAN iterative deconvolution algorithm as a post-processing step. Consistent target localisation across all scenarios is confirmed by two-dimensional radar images obtained from cross-range scanning. The results demonstrate the feasibility of a low-cost bistatic radar platform for short-range sensing applications including security scanning, remote target localisation, and multi-target detection

Bistatic Radar for Multi-Target Detection Using Microstrip Patch Antennas

2026-09-02

PIER C

Vol. 173, 92-102, 2026

doi:10.2528/PIERC26042402

download: 137

High-Gain Ultra-Wideband Half-Moon Monopole Patch Antenna with Metallic Reflector for GPR Systems

Mohammad Ikhwan Haziq Khairul Anuar, Anupma Gupta, Aymen Dheyaa Khaleel, Zahriladha Zakaria, Nurhayati Nurhayati, Abdulrahman Ahmed Ghaleb Amer, Fakhriy Hario Partiansyah, Hafsa Omar, Atul Varshney, Reuben George, Anuar Mohamed Kassim and Ahmed Jamal Abdullah Al-Gburi

In this study, a coplanar waveguide (CPW)-fed half-moon monopole ultra-wideband (UWB) antenna is proposed, simulated, fabricated, and experimentally validated for ground-penetrating radar (GPR) applications. The antenna is specifically designed to provide high forward gain and stable wideband performance via integrating a full-copper metallic reflector. The proposed antenna exhibits good impedance matching and satisfactory reflection coefficient characteristics across the UWB frequency range of 3.1-10.6 GHz. By incorporating the metallic reflector, a significant radiation enhancement is achieved. The antenna attains a peak gain of 8.7 dBi at 6 GHz and maintains a gain above 6.5 dBi throughout the operating bandwidth. This gain improvement and suppression of back radiation are particularly important for GPR systems, where deep subsurface penetration and high-resolution imaging are essential. The integration of a metallic reflector provides a simple yet highly effective approach for gain enhancement without complex structures or advanced materials, as confirmed by both simulated and experimental results. These findings demonstrate the suitability of the proposed antenna for practical high-gain UWB GPR and broadband sensing applications.

High-Gain Ultra-Wideband Half-Moon Monopole Patch Antenna with Metallic Reflector for GPR Systems

2026-08-31

PIER C

Vol. 173, 83-91, 2026

doi:10.2528/PIERC26070202

download: 127

Fast Monostatic Scattering Analysis of Large-Scale Periodic Arrays Using an MMV-CS-CM-SED Method

Yukun Ding, Zhonggen Wang, Wenyan Nie and Quan Sun

Conventional methods face prohibitive computational overhead for multi-aspect monostatic scattering analysis of large-scale finite periodic arrays (LFPAs) due to repetitive preprocessing and full-matrix inversion under wide-angle multiple-incidence scenarios. To meet this challenge, this paper proposes an efficient multi-measurement vector compressive sensing framework combined with characteristic mode subdomain extraction (MMV-CS-CM-SED). It extracts excitation-independent CM-SED basis functions from a coupled subarray, forming a reusable sparse dictionary. Furthermore, we introduce a uniform spatial sampling strategy based on golden-section low-discrepancy sequences, which drastically reduces matrix filling by extracting only a small portion of impedance matrix rows. Finally, the method leverages the joint sparsity of multi-angle coefficients through an MMV model to accelerate the solution process. Numerical results demonstrate that, compared to the accurate subdomain entire-domain (ASED) and method of moments (MoM), the proposed method achieves high radar cross section (RCS) accuracy while reducing total matrix filling and computational time by over 70%, validating its efficiency and accuracy for large-scale array electromagnetic analyses.

Fast Monostatic Scattering Analysis of Large-Scale Periodic Arrays Using an MMV-CS-CM-SED Method

2026-08-31

PIER C

Vol. 173, 67-82, 2026

doi:10.2528/PIERC26042906

download: 90

Marked Self-Exciting Point Process Modeling of Impulsive Electromagnetic Interference in Power Line Communication Systems

Steven O. Awino and Bakhe Nleya

Power line communication (PLC) channels are significantly affected by bursty and impulsive electromagnetic interference (EMI), whose temporal clustering and amplitude variability are not adequately captured by conventional statistical models. Existing approaches often treat impulse arrivals and amplitudes independently, limiting their ability to reproduce the coupled dynamics observed in practical transmission line environments. In this study, a marked self-exciting point process model is proposed for PLC noise characterization, where impulse arrival times are governed by a Hawkes-type process, and amplitudes are represented as stochastic marks. The framework incorporates mark-dependent excitation, allowing higher-amplitude impulses to influence subsequent event occurrences and thereby capture the observed bursty structure. A measurement-driven analysis shows that PLC impulsive noise exhibits short-term temporal dependence and deviation from memoryless behavior, as reflected in skewed inter-arrival distributions, nonlinear complementary cumulative distribution function (CCDF) characteristics, and non-zero autocorrelation at small lags. Parameter estimation indicates dominant baseline activity with moderate self-excitation and rapidly decaying temporal influence. Amplitude modeling revealed a skewed distribution with intermittent high-energy events, whereas extreme value analysis using a generalized Pareto distribution suggested a bounded tail behavior for threshold exceedances. A joint likelihood-based estimation framework was developed to enable practical parameter inference. Validation of measured PLC datasets demonstrated that the proposed model consistently captures both temporal and amplitude characteristics without parameter re-estimation. A comparative analysis with a Poisson model showed clear discrepancies, with a quantified CCDF error of 0.15932, highlighting the limitations of memoryless assumptions. Overall, the proposed marked self-exciting framework provides a physically interpretable and statistically consistent representation of impulsive EMI in PLC systems, offering a robust foundation for improved modeling and mitigation strategies.

Marked Self-Exciting Point Process Modeling of Impulsive Electromagnetic Interference in Power Line Communication Systems

2026-08-31

PIER C

Vol. 173, 62-66, 2026

doi:10.2528/PIERC26061803

download: 158

Design of a Meandered Monopole Antenna for Dual-Band Applications

Tukaram Salunkhe Dhanashri, Selvaraj Imaculate Rosaline and Arokiaswami Alphones

This paper describes the design and analysis of a compact folded monopole antenna based on a Y-shaped meandered configuration, to operate within the 5 GHz to 6.5 GHz frequency range. TThe antenna has a compact size of 40 × 30 mm², and is fabricated on a low-cost FR4 epoxy substrate, making it suitable for easy integration into wireless systems. The main radiating configuration consists of a central vertical feedline connected symmetrically to meandered arms, forming a Y-shaped layout that enables a compact size without affecting radiation efficiency. The antenna is fed through a microstrip line, with the input signal equally distributed to both arms, each functioning as a quarter-wavelength monopole. The antenna demonstrates omnidirectional radiation patterns in both the E and H-planes and achieves a gain of 3\,dB. To ensure human safety, we also performed a specific absorption rate (SAR) analysis using a human baby phantom model. The maximum SAR is 0.128\,W/Kg at both frequencies, well below the acceptable 1.6\,W/kg limit set by the ICNIRP guidelines. The fabricated prototype was tested, and the measured results closely match simulations, validating the antenna's suitability for modern compact wireless applications.

Design of a Meandered Monopole Antenna for Dual-Band Applications

2026-08-30

PIER C

Vol. 173, 53-61, 2026

doi:10.2528/PIERC26071905

download: 91

A Wideband Self-Decoupled 8-Port MIMO Antenna Array Based on Orthogonal Modes for 5G Smart Terminals

Linchong Sun, Han Lin, Zhonggen Wang, Wenyan Nie and Shunqi Liu

This paper proposes a compact 8-port multiple-input multiple-output (MIMO) wideband self-decoupled antenna for 5G mobile terminal applications. Based on an orthogonal mode decoupling scheme, a combination of a loop antenna and an N-shaped antenna is utilized to achieve wideband coverage and high isolation in the N79 (4.35-5.1 GHz) band. Building on this decoupling mechanism, a 5-mm clearance is created between the ground plane and the side frame to mitigate mutual coupling between ports while optimizing impedance matching to broaden the bandwidth. Four antenna modules are symmetrically distributed on the FR4 dielectric side frames, forming a compact 8-port MIMO antenna array. The measured results show that the proposed system achieves consistent isolation better than 30 dB across the target frequency band, an envelope correlation coefficient (ECC) lower than 0.005, and a total radiation efficiency over 73% (averaging 80%). Thanks to its excellent isolation and bandwidth performance in a limited space, this scheme is a highly competitive candidate design for 5G smart terminal applications.

A Wideband Self-Decoupled 8-Port MIMO Antenna Array Based on Orthogonal Modes for 5G Smart Terminals

2026-08-28

PIER C

Vol. 173, 41-52, 2026

doi:10.2528/PIERC26072401

download: 249

A Hybrid-Magnet Rotor Topology for Demagnetization-Resistant PMaSynRMs Using Kriging-NSGA-III Optimization

Fangrong Wang, Wen Kuang and Chaozhi Huang

Conventional ferrite-based permanent magnet-assisted synchronous reluctance motors (PMaSynRMs) suffer from low torque density and are vulnerable to irreversible demagnetization under heavy-load conditions due to the reverse armature field. To address this, this paper proposes a hybrid-magnet rotor topology in which ferrite and NdFeB magnets are arranged in series along the flux path within each U-type flux barrier (NdFeB on the airgap side, ferrite on the inner side), while the three radially layered U-type branches are connected magnetically in parallel. Within each barrier, the magnetomotive forces of the two magnet types superpose to enhance the excitation flux; meanwhile, a dual synergistic mechanism - outer NdFeB shielding and flux shunting via parallel rotor bridges - suppresses the demagnetizing field. To tackle the 15-dimensional optimization problem, a Kriging-NSGA-III framework incorporating Pearson sensitivity screening is established. Finite-element results show that, compared to the benchmark all-ferrite machine, the optimized motor achieves a 20.78% increase in average torque, torque ripple reduction from 18.80% to 8.07%, and 89.49% efficiency. The benchmark exhibits local irreversible demagnetization at 3 times rated d-axis current, whereas the proposed topology shows no observable demagnetization even at 6 times rated current, validating the effectiveness of the proposed hybrid topology and optimization strategy.

A Hybrid-Magnet Rotor Topology for Demagnetization-Resistant PMaSynRMs Using Kriging-NSGA-III Optimization

2026-08-25

PIER C

Vol. 173, 31-40, 2026

doi:10.2528/PIERC26071704

download: 173

An Ultra-High-Performance Wideband Reflective Frequency Selective Surface for Linear Y to X Polarization Conversion Suitable for Target Detection Systems

Shanmugam Muni Rathnam, Veparala Kishen Ajay Kumar, Ramamoorthy Raman, Gajendran Srihari, Shaik Mahaboob Basha and Kattela Pavan Kumar

This manuscript presents a novel compact reflective frequency selective surface (FSS) for wideband polarization conversion, enabling efficient polarization manipulation over the frequency range of 8.2 GHz to 9.5 GHz, which is the X-band spectrum for electromagnetic applications. The proposed FSS consists of a metallic pattern printed on an FR4 substrate with a relative permittivity of ε_r = 4.4, loss tangent of tanδ = 0.02, and thickness of 1.6 mm, backed by a ground plane. This configuration enables reflective-mode operation with a tunable frequency range typically spanning X-band, achieved by optimizing the unit cell's geometrical parameters. The proposed structure provides efficient linear-to-orthogonal polarization conversion over 8.2-9.5 GHz (1.3 GHz bandwidth, center frequency of 8.85 GHz), with a polarization conversion ratio (PCR) exceeding 98%. This frequency range lies within the X-band and provides a fractional bandwidth of approximately 14.69. Under oblique incidence, the proposed FSS maintains a PCR above 90% up to 40°, with only a slight bandwidth reduction, and shows good agreement between simulated and measured results. Owing to its compact nature, excellent angular stability and wide operating bandwidth, the proposed FSS is suitable for radar and wireless communication applications.

An Ultra-High-Performance Wideband Reflective Frequency Selective Surface for Linear y to x Polarization Conversion suitable for Target Detection Systems

2026-08-26

PIER C

Vol. 173, 20-30, 2026

doi:10.2528/PIERC26071404

download: 213

A Decoupling-Stub-Free Flexible MIMO Antenna with Ultra-High Isolation for Ka-Band Conformal Terminals

Chenmeng Wang, Lingming Tong and Wendong Yang

Devices such as drones and low Earth orbit satellites demand antennas that are lightweight, thin, and sufficiently flexible to conform to curved surfaces. At millimetre wave frequencies, however, closely placing multiple antennas inevitably introduces mutual coupling, which degrades communication quality. This paper presents a four element antenna array fabricated on a flexible polyethylene ter-ephthalate (PET) substrate, operating in the 26.21-29.64 GHz band. Unlike conventional approaches that rely on additional decoupling components, our design eliminates interference solely through a centrosymmetric four quadrant layout of the radiating elements, without any auxiliary structures. Measurements show that isolation among all four ports exceeds 46.95 dB; the envelope correlation coefficient (ECC) reaches as low as 0.0000312; and the diversity gain approaches the theoretical limit of 10 dB. The antenna maintains a radiation efficiency above 90% and a gain of 2.40-3.20 dBi, with stable coverage patterns across the entire band. With a thickness of only 0.12 mm, this flexible antenna offers a simple, low cost, high performance solution for conformal ap-plications. The work demonstrates that careful layout design can replace complex decoupling networks, providing a new pathway for lightweight, flexible, large scale antenna arrays in future 5G/6G communication systems.

A Decoupling-Stub-Free Flexible MIMO Antenna with Ultra-High Isolation for Ka-Band Conformal Terminals

2026-08-26

PIER C

Vol. 173, 9-19, 2026

doi:10.2528/PIERC26062903

download: 92

Unbalance Vibration Compensation Control of Outer Rotor Coreless Bearingless Permanent Magnet Synchronous Motor Based on Optimized Secondary-Path Estimation VSS-FXLMS Algorithm

Zelong Zhao, Huangqiu Zhu and Yichen Liu

Rotor mass eccentricity in an outer-rotor coreless bearingless permanent magnet synchronous motor (ORC-BPMSM) causes synchronous unbalance vibration, which degrades suspension stability and limits high-speed operation. To suppress this vibration, an optimized secondary-path estimation variable-step-size filtered-x least mean square (OSPE-VSS-FxLMS) feedforward compensation method is proposed. First, the rotor unbalance vibration mechanism is derived from the suspension force model. Then, a hyperbolic tangent-exponential (tanh-exp) function is introduced to adaptively regulate the FxLMS step size, improving the trade-off between convergence speed and steady-state error. Meanwhile, a normalized least mean square (NLMS)-based online secondary-path estimation strategy is developed to reduce gradient deviation caused by secondary-path mismatch. Simulations and experiments are conducted under constant-speed and acceleration conditions. Compared with the uncompensated condition at 3000 r/min, the displacement vibration amplitudes in the x- and y-direction are both reduced to 11 μm, corresponding to a reduction of about 69.4%. The effectiveness of the proposed unbalance vibration compensation method is confirmed by both simulated and experimental results.

Unbalance Vibration Compensation Control of Outer Rotor Coreless Bearingless Permanent Magnet Synchronous Motor Based on Optimized Secondary-Path Estimation VSS-FxLMS Algorithm

2026-08-25

PIER C

Vol. 173, 1-8, 2026

doi:10.2528/PIERC26060705

download: 122

Accurate Modelling of the Nonlinear Magnetic Restoring Force and the Electromechanical Transduction Coefficient in an Electromagnetic Vibration Energy Harvester

Merwan Hebbache, Naamane Mohdeb, Hocine Bouchekhou, Nabil Ikhlef, Hicham Allag and Abdelghani Kimouche

Electromagnetic harvesters based on magnetic levitation have emerged as particularly attractive systems owing to their contactless suspension, low mechanical damping, and inherently nonlinear stiffness behavior, which are suited to low-frequency ambient excitation. The investigated harvester consists of a levitating magnet suspended between two fixed outer magnets via repulsive magnetic forces, with a pickup coil converting oscillatory motion into electrical energy under base excitation. The primary source of difficulty in this system is the nonlinear magnetic restoring force F_mag and the electromechanical transduction coefficient γ, which must be pre-characterized via semi-analytical or finite element methods before any solution can be attempted. Therefore, the accurate pre-characterization of both F_mag and γ is the essential foundation of the entire modelling process. A Fourier space semi-analytical approach is proposed and developed, transforming a three-dimensional magnetostatic problem into a computationally efficient one-dimensional spectral calculation without remeshing. The semi-analytical predictions were validated against COMSOL finite element simulations, and their strong mutual agreement confirmed the accuracy of the proposed method before embedding it into the motion's coupled nonlinear equations.