PIER C | PIER Journals

2025-12-20

PIER C

Vol. 163, 210-221, 2026

doi:10.2528/PIERC25101902

download: 21

A Quad-Band Dipole Antenna with Dual I-Shaped Stubs and V-Shaped Etching for Surveying Drone Applications

Suwat Sakulchat, Sommart Promput, Watcharaphon Naktong and Panuwit Thongbor

This research presents a quad-band dipole antenna for use with a surveying drone. The dipole antenna structure design employs the technique of adding I-shaped stubs and V-shaped etching, using aluminum plates with a strong and lightweight structure, with a thickness of 2 mm, a width of 1,325 mm, and a length of 190 mm. The antenna is designed to support frequency bands according to standards (VOR: Very High Frequency Omnidirectional Range) at 118 MHz, (GS: Glide Slope) at 336 MHz, (DME: Distance Measuring Equipment) at 1231 MHz, and WiFi at 2.45 GHz. From the calculations and simulations using the CST program, optimal parameter values were obtained, leading to the fabrication of a prototype antenna and the testing of its antenna properties. The results showed reflection coefficient values of -21.87 dB (108-118 MHz), -12.76 dB (328-336 MHz), -11.99 dB (962-1231 MHz), and -21.79 dB (2400-2480 MHz), which covers the VOR/GS/DME/ IEEE 802.11b/g/n standards. The antenna gain values are 1.12, 2.38, 3.76, and 4.00 dBi, respectively, with an omnidirectional radiation pattern, and the prototype dipole antenna tested with a drone was found to operate normally in the low frequency range of 108-118 MHz, the first mid frequency range of 328-336 MHz, the second mid frequency range of 962-1231 MHz, and the high frequency range of 2400-2480 MHz.

A Quad-Band Dipole Antenna with Dual I-Shaped Stubs and V-Shaped Etching for Surveying Drone Applications

2025-12-19

PIER C

Vol. 163, 198-209, 2026

doi:10.2528/PIERC25102102

download: 31

Unbalance Vibration Compensation Control of Permanent Magnet Assisted Bearingless Synchronous Reluctance Motor Based on LMS Filter Algorithm Optimized by BPNN

Tianliang Du and Huangqiu Zhu

To address the rotor vibration induced by rotor unbalance in a permanent magnet assisted bearingless synchronous reluctance motor (PMa-BSynRM), a feedforward compensation control method based on the Least Mean Squares (LMS) adaptive filtering algorithm, optimized by a Back Propagation Neural Network (BPNN), is proposed. Firstly, the operating principle of the PMa-BSynRM is introduced, and the mechanism of rotor unbalance vibration is analyzed. Secondly, a feedforward compensation controller is developed to extract the vibration signal and suppress rotor vibration. The BPNN is employed to adaptively adjust the LMS step size, thereby enhancing convergence speed, accuracy, and anti-interference capability. Furthermore, to overcome the inherent limitations of the BPNN, a hybrid optimization strategy that integrates particle swarm optimization (PSO) with an improved genetic algorithm (IGA) is adopted to optimize the initial weights and thresholds of the BPNN. Finally, a rotor unbalance vibration compensation control system for the PMa-BSynRM is established. Simulation and experimental results verify that the proposed control algorithm effectively reduces radial displacement and suppresses unbalanced vibration, while also exhibiting strong anti-interference performance and robustness.

Unbalance Vibration Compensation Control of Permanent Magnet Assisted Bearingless Synchronous Reluctance Motor Based on LMS Filter Algorithm Optimized by BPNN

2025-12-19

PIER C

Vol. 163, 187-197, 2026

doi:10.2528/PIERC25103001

download: 16

A 5G NR N79 Band Compact MIMO Antenna with DGS-Based Isolation Enhancement

Prabhu Kumar Kothavari and Venkata Rajasekhar Nuthakki

A compact four-port multiple-input multiple-output (MIMO) antenna operating on the N79 band (4.4-5.0 GHz) is designed for use in 5G wireless communication systems. The suggested antenna is synthesized over an FR4 epoxy substrate with a relative permittivity of ε_r = 4.4, and a standard height of 1.2 mm. The overall dimensions of the antenna are 45 × 45 × 1.2 mm³, making it suitable for insertion into miniature 5G-enabled portable devices. A novel defected ground structure (DGS) is proposed, employing the strategic placement of two stubs of unequal lengths within the shared ground plane to effectively mitigate surface-wave propagation and thereby suppress mutual coupling among antenna elements. Thus, the design achieves considerable isolation, with a level below -20 dB across the targeted operational band. The suggested antenna operates at 4.67 GHz with a peak gain of 2.83 dBi and a radiation efficiency of 92%. The performance of the MIMO antenna was comprehensively assessed using standard diversity metrics, achieving an 0.01 envelope correlation coefficient (ECC), a diversity gain (DG) of 9.99 dB, a channel capacity loss (CCL) of 0.36 bits/s/Hz, and a mean effective gain (MEG) consistently below -3 dB. A strong correlation between experimental and simulated findings points towards the robustness of the suggested design. With its compact size, high isolation, and excellent MIMO performance, the antenna demonstrates strong potential for integration into sub-6 GHz 5G MIMO wireless communication systems.

A 5G NR n79 Band Compact MIMO Antenna with DGS-Based Isolation Enhancement

2025-12-19

PIER C

Vol. 163, 181-186, 2026

doi:10.2528/PIERC25103006

download: 17

Broadband Validation of a 2D-FDTD-PML and Nelder-Mead Framework for Liquid Permittivity Extraction

Omaima Talmoudi, Lahcen Ait Benali, Jaouad Terhzaz and Abdelwahed Tribak

A methodology for estimating the complex permittivity of liquid dielectrics is presented in a rectangular waveguide using the Ku-band (10-15 GHz, WR75). A two-dimensional finite difference time-domain (FDTD) model with perfectly matched layers (PMLs) serves as the forward solver, and TE₁₀ modal projection provides the simulated scattering parameters. Subsequently, a gradient-free Nelder-Mead inversion extracts the real and imaginary parts of the permittivity from the measured S₁₁ and S₂₁ parameters. This approach is implemented in a multilayer fixture, which enables leak-tight loading while remaining analytically simple. Validation on air and water shows good agreement between simulation and measurement across 10-15 GHz, and results at 12 GHz are consistent with independent X-band extractions. This approach is computationally efficient, practical for experimentation, and can be extended to other liquids and multilayers.

Broadband Validation of a 2D-FDTD-PML and Nelder-Mead Framework for Liquid Permittivity Extraction

2026-12-19

PIER C

Vol. 163, 168-180, 2026

doi:10.2528/PIERC25092502

download: 49

Experimental Results and Analysis of a 2-Receiver Midrange Wireless Power Transfer System in Seawater

Xiaoliang Li, Wangqiang Niu and Xianwen Zhou

Due to the high electrical conductivity, relative permittivity, and magnetic permeability of seawater, the propagation behavior of electromagnetic fields differs significantly from that in air. The conductive nature of seawater causes strong eddy current loss and magnetic field attenuation, thereby reducing the effective coupling coefficient and resulting in frequency detuning between the transmitter and receiver coils. Moreover, the marine environment introduces parasitic impedance paths and additional energy dissipation due to the conductive medium, which further decreases transmission efficiency. These unique electromagnetic characteristics make the design and optimization of wireless power transfer (WPT) systems in seawater more complex and challenging than in air, motivating this study to develop and analyze a dual-receiver WPT architecture that improves midrange transmission efficiency under underwater conditions. To address this issue, a single-transmitter dual-receiver (1TX-2RX) WPT system operating in the 300-550 kHz frequency range is designed and implemented. Experimental results demonstrate that, under midrange transmission in seawater, the efficiency of the proposed 2RX architecture improves markedly from 12% in the 1RX system to 25%, while maintaining stable output performance under various receiver coil misalignment conditions. In addition, compared with operation in air, the optimal operating frequency of the 2RX system in seawater shifts leftward from approximately 460 kHz to 410 kHz. To better characterize the impact of seawater on transmission performance, complex impedance and mutual inductance parameters are incorporated into the conventional circuit model, enabling effective representation of the additional losses and coupling attenuation induced by the conductive medium. The predicted load voltage is consistent largely with the experimental measurements, validating the accuracy and applicability of the proposed modeling approach. Overall, this study not only verifies experimentally the feasibility of improving midrange transmission efficiency through a dual-receiver architecture but also establishes theoretically a circuit modeling method suited better for seawater environments, providing useful insights for the design and optimization of marine WPT systems.

Experimental Results and Analysis of a 2-Receiver Midrange Wireless Power Transfer System in Seawater

2025-12-19

PIER C

Vol. 163, 161-167, 2026

doi:10.2528/PIERC25100401

download: 17

Research and Design of Non-Contact Electromagnetic Flowmeter

Jing Zeng, Haoxuan Xu, Hongjia Liu, Jing Liu, Yuanyuan Li, Guo-Qiang Liu and Errun He

Liquid metals possess significant application value in key sectors such as new energy, nuclear energy, and metallurgy due to their excellent fluidity, high electrical and thermal conductivity, and remarkable high-temperature stability. Accurate flow measurement during their application is crucial for ensuring system safety. However, conventional flow measurement techniques struggle to guarantee long-term stability under high-temperature conditions. To address this challenge, this paper proposes a non-contact alternating current excitation electromagnetic flowmeter. The design generates a stable alternating magnetic field via an excitation coil and employs externally mounted, differentially connected induction coils as the sensing element. This configuration enables non-contact measurement of liquid metal flow within metal pipes, fundamentally overcoming the reliability degradation issues associated with direct sensor contact with the measured medium. Experimental results demonstrate that the system has the potential to operate stably at a high temperature of 600°C and has achieved a high measurement accuracy of 3%.

Research and Design of Non-Contact Electromagnetic Flowmeter

2025-12-18

PIER C

Vol. 163, 149-160, 2026

doi:10.2528/PIERC25102804

download: 24

A Novel Wideband Coaxial-to-Rectangular Waveguide Transition Integrated with a Septum Horn Antenna for C-Band Satellite

Ajitesh and Manoj Kumar Meshram

In this paper, a novel wideband coaxial-to-rectangular waveguide transition integrated with a septum horn antenna is proposed for C-band satellite communication applications. The design employs a modified supershape excitation probe, derived from an extended superformula, to achieve smooth impedance transformation and broadband performance. Initially, the probe geometry is optimized through parametric simulations to validate its effectiveness within a rectangular waveguide structure. The transition is then effectively incorporated into a stepped septum horn antenna that facilitates dual circular polarization through a compact dual-feed mechanism. The septum structure ensures efficient conversion of linearly polarized modes into left-hand and right-hand circularly polarized waves, while maintaining high isolation and low axial ratio. An equivalent circuit model is developed to provide analytical insight into the impedance behavior. A prototype antenna is fabricated, and its performance is validated through measurements. The measured results confirm reflection coefficients below -10 dB across 4.6-8.6 GHz, peak gain of 15.8 dBi, and inter-port isolation exceeding 20 dB. Furthermore, the antenna achieves a 3 dB axial ratio bandwidth of 76.9%. A comparison with state-of-the-art designs demonstrates the superior performance and design efficiency of the proposed antenna architecture.

A Novel Wideband Coaxial-to-Rectangular Waveguide Transition Integrated with a Septum Horn Antenna for C-Band Satellite

2025-12-18

PIER C

Vol. 163, 139-148, 2026

doi:10.2528/PIERC25082005

download: 36

Inertial Forces from Relativistic and Thermal Effects of Electromagnetic Frequency Sweeps

Roberto Bernardo Benedicto Ovando

We investigate the thermal and relativistic effects produced when an electrically conductive object is moving in tandem with a source of a variable electromagnetic field. First, we derive an energy–frequency relation to quantify the temperature rise induced by such a field. This relation is then combined with the Lorentz-Fitzgerald contraction and time dilation from special relativity to identify a force, F_c, required to reconcile energy conservation between stationary and moving observers. We further relate F_c to the relativistic energy of a moving mass, extending the analysis to objects without electrical conductivity. This connection leads to the prediction of an inertial force F_cf generated by the frequency sweep of an electromagnetic wave (whether caused by relative motion or by internal modulation) that interacts with mass regardless of its electrical properties.

Inertial Forces from Relativistic and Thermal Effects of Electromagnetic Frequency Sweeps

2025-12-17

PIER C

Vol. 163, 128-138, 2026

doi:10.2528/PIERC25092301

download: 27

Miniaturized High-Efficiency Wideband Multi-Slot Antenna for Radar, Military, and 5G Applications for SDG-9

Swati Varun Yadav, Manish Varun Yadav, Himanshu Gupta and Vikas Gupta

A compact wideband antenna with a multi-slot configuration is proposed for radar, military, and modern wireless communication systems. The antenna is fabricated on an FR-4 substrate with overall dimensions of 14 × 16 × 1.5 mm³, corresponding to a miniaturized electrical size of 0.163λ × 0.187λ × 0.017λ₀ at 3.5 GHz. To achieve broad impedance bandwidth and improved matching, multiple slots are etched on both the patch and ground surfaces. Experimental validation shows that the antenna effectively covers the 3.5-14 GHz frequency range, offering nearly 120% fractional bandwidth. Within this spectrum, it delivers a peak gain of 5.1 dB and a maximum radiation efficiency of about 89%, ensuring stable and low-loss performance. The compact structure maintains consistent radiation characteristics, making it suitable for portable and defense-oriented devices. Its ability to support Sub-6 GHz and 5G bands further enhances its applicability in next-generation communication platforms.

Miniaturized High-Efficiency Wideband Multi-Slot Antenna for Radar, Military, and 5G Applications for SDG-9

2025-12-17

PIER C

Vol. 163, 120-127, 2026

doi:10.2528/PIERC25092603

download: 37

Design of Cascaded Circular Ring Semicircular Cresent Shaped Multiband Antenna for UWB, WLAN, WiMAX and 5G Midband Applications

Chevala Rambabu, Kaza Srilakshmi, Vasudha Vijayasri Bolisetty, Udara Yedukondalu and Kottapadikal Vinodan Vineetha

In this paper we report a cascaded circular ring antenna with semicircular C-shaped radiating slots for multiband applications. The novelty of this paper lies with three techniques as follows: cascading circular rings, semicircular C-shaped slots and complimentary split ring resonators embedded on the ground are included in the paper. The dimensions with optimised values are 35 × 35 × 1.61 mm³. The antenna operates from 2.124 GHz to 8.284 GHz, and it is deposited on a 1.6 mm thick FR-4 substrate. The radiating patch is built on the substrate; it is made by developing multiple circular ring structures to develop a cascaded ring-like pattern that provides the wideband response. The antenna successfully resonated with a wide bandwidth of 6.16 GHz in the span of 2.124 GHz to 8.284 GHz. The ground features a half hexagonal slot that is embedded within the larger etched rectangular slot. An equivalent circuit with R-L-C elements is developed. The resonating bands are obtained at 3.0 GHz, 5.89 GHz, and 7.07 GHz with reflection coefficients of -21.3 dB, -19.7 dB, and -26.7 dB, respectively. The optimised design operates at UWB, WLAN, WiMAX, and 5G midband applications.

Design of Cascaded Circular Ring Semicircular Cresent Shaped Multiband Antenna for UWB, WLAN, WiMAX and 5G midband Applications

2025-12-17

PIER C

Vol. 163, 113-119, 2026

doi:10.2528/PIERC25091906

download: 29

Frequency- and Phase-Tunable Coupler Based on Three-Line and Four-Line Coupled Lines

Bo Huang, Yongle Wu, Shuchen Zhen, Weimin Wang and Jinchun Gao

This paper proposes a reconfigurable 3-dB coupler with tunable phase and frequency characteristics based on triple-line loaded varactor diodes. The core structure employs a four-line coupling configuration to ensure strong coupling characteristics and stability. Through integrated theoretical analysis and experimental verification, the coupler demonstrates a center frequency tuning range of 1.8-2.4 GHz with continuous phase difference adjustment from 40° to 140°. Measured results indicate that high isolation (> 20 dB) and low return loss (< -20 dB) can be obtained.

Frequency- and Phase-Tunable Coupler Based on Three-Line and Four-Line Coupled Lines

2025-12-16

PIER C

Vol. 163, 108-112, 2026

doi:10.2528/PIERC25093005

download: 26

Compact Millimeter-Wave Microstrip Dual-Band Filter Using the Ring Type Structure

Wei Zhao, Mingen Tian, Ziyan Lu, Hailong Wang, Yiming Zhang and Huali Zhu

A compact microstrip dual-band filter using stepped-impedance resonators (SIRs) is proposed. The ring-type structure is used to minimize the size of the filter, and the location of the input/output excitation port is used to adjust the filter's performance. A dual-band filter has been fabricated and measured to verify the performance of the proposed configuration. The results show that the filter exhibits two passbands, centered at 30.5 GHz and 35.9 GHz, with fractional bandwidths of 7.2% and 5.6%, respectively. The corresponding insertion losses at the center frequencies are 2.7 dB and 3.3 dB. The proposed filter configuration shows great potential for applications in next-generation 5G and satellite communication systems requiring compact and high-performance multi-band filters.

Compact Millimeter-Wave Microstrip Dual-Band Filter Using the Ring Type Structure

2025-12-16

PIER C

Vol. 163, 100-107, 2026

doi:10.2528/PIERC25091708

download: 59

Dielectric Response and Transient Potential Characteristics of Grounding Electrodes Considering the Frequency Effect of Frozen Soil

Wei Shen, Mingxi Zhu, Xinmin Li and Ziming He

This study investigates the electrical characteristics of grounding electrodes in seasonal frozen soil through experimental and simulation approaches. Experimental measurements reveal the variation patterns of soil resistivity and dielectric constant within the frequency range of 100 Hz-10 MHz at different temperatures. The results indicate that decreasing temperature leads to increased resistivity and decreased dielectric constant, with both parameters tending to stabilize at high frequencies. Computations based on the method of moments demonstrate that accounting for the frequency dependence of frozen soil reduces the impedance magnitude by 20%-40% in the high-frequency range and results in more complex resonant behavior. When the length of the grounding electrode is less than the freezing depth, the high-frequency capacitive effect is significantly enhanced. Time-domain analysis shows that under lightning impulse conditions, the potential reduction is approximately 22% during the first return stroke and can reach up to 42% in subsequent return strokes. The study concludes that the frequency dependence of the electrical parameters of frozen soil has a considerable influence on the response of grounding electrodes and should be considered in modeling and lightning protection design.

Dielectric Response and Transient Potential Characteristics of Grounding Electrodes Considering the Frequency Effect of Frozen Soil

2025-12-15

PIER C

Vol. 163, 91-99, 2026

doi:10.2528/PIERC25100901

download: 48

Optimization of a Multi-Function Car-Roof Antenna Using Deep Learning Method

Dingwen Tan, Hexue Liu, Bing Xu, Xiaoming Liu, Shuo Yu and Lu Gan

This paper presents a dual-band car-roof antenna, which holds potential applications for 5G-MIMO, WLAN and V2X. The proposed antenna is installed within a shark-fin room on the roof of vehicles. The proposed design consists of two parts, the diversity antenna and the main antenna. To mitigate spatially selective fading and ensure coverage, both the diversity and main antennas have omnidirectional radiation patterns in the azimuth plane. To reach a multi-function design, deep learning method is used for optimization based on MATLAB-HFSS-API. Notably, the optimized antenna reaches a compact size of 27 mm × 30 mm × 2 mm. The antenna have two bands (-10 dB), including 3.35-3.75 GHz and 4.76-7.19 GHz, covering China Telecom (3.4-3.5 GHz), China Unicom (3.5-3.6 GHz), China Mobile (4.8-4.9 GHz), WLAN (5.15-5.35 GHz, 5.725-5.850 GHz), unlicensed Wi-Fi (5.850-5.895 GHz), V2X (5.895-5.925 GHz) and Wi-Fi 6E (5.925-7.125 GHz). The full-wave simulation results are in satisfactory consistency with the measured ones.

Optimization of a Multi-function Car-roof Antenna Using Deep Learning Method

2025-12-15

PIER C

Vol. 163, 81-90, 2026

doi:10.2528/PIERC25101901

download: 27

Shorted Microstrip Line Fed Wideband Design of E-Shape Microstrip Antenna Loaded with Printed Rectangular Resonator

Venkata A. P. Chavali and Amit A. Deshmukh

The shorted microstrip line fed design of an E-shape microstrip antenna loaded with a printed rectangular loop resonator is presented for wideband response on a thinner substrate. Wideband response is attributed to the optimum inter-spacing between the TM_1/2,0 resonant mode of shorted microstrip line feed, with respect to TM₁₀ and modified TM₀₂ modes on rectangular patch and TM₂₀ mode on the printed rectangular loop. The design on a substrate of thickness 0.046λ_g achieves bandwidth of 227 MHz (23.56%) with a peak broadside gain of 7.1 dBi. The selection of microstrip line feed achieves wideband response on thinner substrate and harmonic rejection to the higher band frequencies. A methodology to design similar antennas as per specific wireless application is presented that yields similar result. An experimental verification has been carried out in the proposed design, which shows close agreement with the simulation.

Shorted Microstrip Line Fed Wideband Design of E-Shape Microstrip Antenna Loaded with Printed Rectangular Resonator

2025-12-14

PIER C

Vol. 163, 73-80, 2026

doi:10.2528/PIERC25071401

download: 74

Metasurface-Driven Improvement in MIMO Antenna Performance by Addressing Mutual Coupling

Safia Jaouad, Chaymae Chahboun, Mohamoed Ali Ennasar, Otman El Mrabet, Jesus Ramon Perez Lopez, Mohsine Khalladi and Mariem Aznabet

In this paper, a metasurface is proposed as an effective solution to enhance the performance of MIMO antennas by reducing mutual coupling. This reduction is attributed to the metasurface's negative permeability at the resonant frequency, which helps to block waves propagating between the two adjacent structures. The designed metasurface consists of a 2D array of omega-shaped resonators placed over two linearly polarized patch antennas. Measurement results show a 15 dB reduction in coupling when the metasurface is positioned 0.14λ₀ above two closely spaced antennas separated by 0.06λ₀ at a resonant frequency of 2.85 GHz. Additionally, improvements in other characteristics of the whole structure, such as gain and radiation efficiency, were also observed. Such an achievement has not been reported in the literature on previous metasurface-based decoupling methods. This technique can be useful for massive multiple input multiple output (mMIMO) systems for wireless communications.

Metasurface-driven Improvement in MIMO Antenna Performance by Addressing Mutual Coupling

2025-12-13

PIER C

Vol. 163, 60-72, 2026

doi:10.2528/PIERC25091202

download: 132

Matrix Square Root Based Differentiable Rcwa Implementation for High-Performance Parallel Computing

Frank Van der Ceelen, Yifeng Shao and Wim M. J. Coene

Rigorous Coupled-Wave Analysis (RCWA) is a semi-analytical method, used to determine the optical response of nanostructures, such as meta-materials. Recently, the ability to combine RCWA with automatic differentiation for optical response optimization has been demonstrated. We seek to build upon this use by attempting to address RCWA's poor performance on parallel computer architecture, stemming from the presence of an eigendecomposition. We do this by outlining an alteration of RCWA, which replaces the eigendecomposition with a matrix square root and matrix exponential evaluation. Furthermore, we demonstrate that these matrix functions can be evaluated using algorithms which are both differentiable and readily evaluated in parallel. Finally, we show that replacing the eigendecomposition with these matrix functions resolves the bottleneck and paves the way for higher-accuracy parameter retrieval using RCWA approaching real-time performance, without compromising stability.

Matrix Square Root Based Differentiable RCWA Implementation for High-Performance Parallel Computing

2025-12-12

PIER C

Vol. 163, 50-59, 2026

doi:10.2528/PIERC25081301

download: 79

Integral Sliding Mode Speed Control of PMSM Based on Novel Fuzzy Exponential Reaching Law

Zhonggen Wang, Jinpeng Ma and Wenyan Nie

To enhance the speed control performance of permanent magnet synchronous motor (PMSM) drive systems, a novel sliding mode control (SMC) strategy based on a new fuzzy exponential reaching law (NFERL) is proposed. The law enhances the traditional exponential reaching law by introducing a system-state-dependent power term and a fuzzy term that adapts the reaching speed based on the sliding mode function. A hyperbolic tangent function replaces the high-frequency switching term to suppress chattering. This control strategy helps reduce current ripples and torque pulsations, and improves the stability and response speed of system operation. Additionally, to address the issue that the system is susceptible to unknown disturbances, a sliding mode disturbance observer (SMDO) is designed to estimate the total disturbance of the system, and the estimated disturbance is fed forward into the composite speed controller. Finally, the introduced control strategy is validated using MATLAB/Simulink simulations and a motor experimental platform. Both simulated and experimental results demonstrate that the new reaching law effectively reduces the startup speed overshoot of the PMSM compared to the traditional law, while also achieving faster convergence, reduced chattering, and superior anti-disturbance performance.

Integral Sliding Mode Speed Control of PMSM Based on Novel Fuzzy Exponential Reaching Law

2025-12-12

PIER C

Vol. 163, 43-49, 2026

doi:10.2528/PIERC25091705

download: 45

Improvement of Isolation and Bandwidth of Notch Ultra-Wideband MIMO Antenna on Metamaterial Wall

Shuming Liu, Jingchang Nan and Yifei Wang

This paper presents a novel notch-based ultra-wideband (UWB) MIMO antenna with a metamaterial wall (MLB-MW) designed to significantly enhance the isolation and operational bandwidth between antenna elements. The antenna adopts a 2 × 1 notch UWB structure, integrating a metamaterial wall made of metallic lines, with an overall size of 20 × 40 × 1.6 mm³, and utilizes an FR-4 dielectric substrate (ε_r = 4.4, tanδ = 0.02). By leveraging the μ-negative characteristics of the MLB-MW, the antenna achieves a 10 dB improvement in isolation across the C, X, and Ku frequency bands. Its impedance bandwidth (|S₁₁| < -10 dB) extends from 6.09-13.07 GHz to 5.51-15 GHz, with a relative expansion rate of 36%. Additionally, key performance parameters of the MIMO antenna are comprehensively evaluated: the envelope correlation coefficient (ECC) remains below 0.01 across the entire frequency band; the diversity gain (DG) is close to 10 dB; and the total active reflection coefficient (TARC) stays below -10 dB across the entire operating band, indicating excellent channel independence and diversity performance. Experimental results verify the feasibility and effectiveness of this antenna in 5G base station applications.

Improvement of Isolation and Bandwidth of Notch Ultra-Wideband MIMO Antenna on Metamaterial Wall

2025-12-12

PIER C

Vol. 163, 35-42, 2026

doi:10.2528/PIERC25091703

download: 95

Design and Analysis of High Isolation Four Port MIMO Antenna for N77 Band 5G Communication

Ramesh Manikonda, Govindarao Tamminaina and Subhashini Gulla

This paper proposes a four-port multiple-input multiple-output (MIMO) antenna for 5G communication. The reference hexagonal antenna with WI-FI slots is designed on FR-4 substrate. Next, four reference antennas are arranged orthogonal to each other for reduction of isolation. The overall dimensions of WI-FI slot four port MIMO antenna is 60×60×1.6 mm³, and it is implemented on an FR-4 substrate with defective ground structure. With an impedance bandwidth of 1 GHz(Giga Hertz), the suggested MIMO antenna operates in the frequency range of 3.3 to 4.3 GHz. The mutual coupling is more than 23 dB among all ports. Furthermore, the MIMO antennas' channel capacity loss (CCL), diversity gain (DG), and envelope correlation coefficient (ECC) are estimated. The parameters are measured using anritsu MS2037C Vector Network Analyzer(VNA).

Design and Analysis of High Isolation Four Port MIMO Antenna for N77 Band 5G Communication

2025-12-11

PIER C

Vol. 163, 20-34, 2026

doi:10.2528/PIERC25091603

download: 82

Multilayer Waveguide Bandpass Filters Based on Subwavelength CSRR and Omega Type Inclusions

Ivan Eduardo Diaz Pardo, Juan Domingo Baena Doello, Carlos Arturo Suarez Fajardo and Hector Guarnizo

This paper presents the design, modeling, and experimental validation of multilayer waveguide bandpass filters employing two subwavelength resonator topologies: complementary split-ring resonators (CSRRs) and Ω-type cells. A hybrid methodology is adopted, combining equivalent circuit models, polarizability extraction from scattering parameters, and full-wave simulations. Mirrorsymmetric configurations are introduced to suppress frequency splitting and improve band uniformity. For both CSRR and Ω arrays, equivalent LC parameters are derived and incorporated into a transmission-matrix framework, enabling accurate prediction of resonant behavior in cascaded layers. Numerical simulations in WR340 waveguides demonstrate that CSRR arrays achieve narrowband responses with high selectivity, while Ω-cells provide wider passbands and improved tolerance to interlayer spacing. Prototypes fabricated on high-purity aluminum sheets were measured using a vector network analyzer, confirming the theoretical and simulation results. The experimental data show close agreement with the proposed model, validating the scalability of the approach to multilayer designs. Quantitatively, the mirror-symmetric CSRR filter exhibits a center frequency of 2.49 GHz, a fractional bandwidth of 1.8%, and an insertion loss of 1.26 dB, whereas the proposed Ω-based configuration achieves a 2.41 GHz center frequency, 5.6% fractional bandwidth, and only 0.27 dB insertion loss. These results show that the Ω topology attains a wider fractional bandwidth and the consequently lower insertion loss predicted by fractional-bandwidth theory, rather than a reduction of intrinsic resonator loss. The proposed framework thus provides a systematic and efficient route for metamaterial filter synthesis, bridging analytical models, numerical simulations, and experimental validation.

Multilayer Waveguide Bandpass Filters Based on Subwavelength CSRR and Omega Type Inclusions

2025-12-11

PIER C

Vol. 163, 11-19, 2026

doi:10.2528/PIERC25101505

download: 59

A Flexible Hexagonal Loop Monopole Antenna with Novel Embedded EBG for SAR Reduction in WBAN

Shital B. Gundre and Varsha R. Ratnaparkhe

This paper introduces a novel compact, flexible hexagonal loop shaped patch antenna embedded with a novel electromagnetic bandgap (EBG) structure designed for ISM band operation, targeting 2.45 GHz wearable applications in close proximity to the human body. The EBG unit cell is formed using a rectangular patch which has nested U shaped slots with a stretched strip of inverted U shaped slot at bottom. Both hexagonal loop antenna and the 2 × 2 EBG array are simulated using Ansys HFSS (High Frequency Structure Simulator). A key aim of this research is to achieve the specific absorption rate (SAR) reduction. The effectiveness of the EBG array structure in reducing surface waves and dropping down the SAR is demonstrated using a multilayer human tissue equivalent phantom comprising skin, fat, muscle, bone layers, confirming obtained SAR values are within the safety limits set by regulatory authorities. The simulation results are verified and validated by the fabricated antenna experimental measurements. Furthermore, the antenna was experimentally assessed in terms of its performance under bending and in practical on-body conditions.

A Flexible Hexagonal Loop Monopole Antenna with Novel Embedded EBG for SAR Reduction in WBAN

2025-12-10

PIER C

Vol. 163, 1-10, 2026

doi:10.2528/PIERC25091605

download: 39

Multi-Mode Dual Five-Phase Hybrid Excitation Motor High Efficiency Control Based on Gradient Descent

Yu Nan, Ye Yuan, Zhenzhen Kong, Xiaozhou Yang, Dong Mu and Fan Yang

The multi-mode dual five-phase hybrid excitation (MM-DFHE) motor, owing to its unique dual-stator configuration, is capable of operating in four distinct modes, offering exceptional operational flexibility. However, this flexibility introduces a control challenge, particularly in Mode IV where the auxiliary stator acts as both an exciter and a torque producer. The additional current variables in this mode lead to suboptimal current distribution, compromising efficiency and dynamic response. To address this, this paper proposes a novel low-loss current optimization control strategy. The key contribution is a Gradient Descent (GD) based online optimization algorithm that dynamically distributes the auxiliary excitation current, specifically tailored for the improved Mode IV operation. This approach resolves the trade-off between loss minimization and dynamic performance prevalent in conventional methods. Simulated and experimental results demonstrate that the proposed strategy reduces total copper loss by up to 13% compared to conventional methods.