PIER C | PIER Journals

2026-05-14

PIER C

Vol. 170, 202-209, 2026

doi:10.2528/PIERC26041401

download: 5

A Unified Conformal FDTD Formulation Based on Harmonic Mean Weighting for Dielectric and PEC Objects

Cuihua Li, Haofeng Wang, Jun Zheng and Minquan Li

To address the need to differentiate between dielectric and perfect electric conductor (PEC) conformal methods in the finite-difference time-domain (FDTD), this study proposes a conformal approach based on the harmonic mean to achieve a unified formulation. In this approach, the relevant electromagnetic parameters are weighted using harmonic mean weighting, enabling a conformal implementation within the FDTD framework. Both dielectric and PEC conformality are incorporated into a single mathematical framework, allowing for a unified treatment in the FDTD. The proposed method provides a consistent formulation that can be seamlessly integrated with standard FDTD procedures while ensuring high compatibility and accuracy of the results. The conformal method based on harmonic mean requires only 60% of the computational time and 36% of the memory compared to the CST method, indicating its high computational efficiency. Furthermore, it demonstrates strong applicability to complex biological models, such as specific absorption rate (SAR) calculations in the human head. This approach is particularly well suited for RF device design and biomedical applications, offering improved modeling efficiency and reliability.

A Unified Conformal FDTD Formulation Based on Harmonic Mean Weighting for Dielectric and PEC Objects

2026-05-14

PIER C

Vol. 170, 194-201, 2026

doi:10.2528/PIERC26031902

download: 10

EMI Filter Parameter Design Optimization Based on Improved Particle Swarm Algorithm

Jian Zheng, Fang Liu, Shuangyin Cheng, Zhenwei Zhang and Zhijie Chen

When designing the parameters of electromagnetic interference filters in BUCK rectifiers using a particle swarm optimization algorithm, the resulting solution set tends to fall into local optima, resulting in a lower cost-performance ratio for the filters. Therefore, an optimization scheme for the parameter design is proposed. First, a multi-objective optimization model is established, with common-mode capacitance and inductance, as well as differential-mode capacitance as decision variables, conducted noise and cost as the objective function, and conducted noise limits and leakage current as constraints. Next, three improvements are made to the conventional algorithm, classifying initialization for the particle population, dividing the total number of iterations into stages with differentiated handling, and implementing an adaptive early termination for iterations, thereby an improved algorithm is obtained. Finally, both the improved and conventional algorithms are applied to solve the optimization model, yielding two types of optimal solutions: performance-prioritized and cost-prioritized solutions. The comparison results show that, between the two optimal solutions, the performance of the improved algorithm is similar to that of the conventional algorithm, but its cost is reduced by 28.37% and 53.14%, respectively. Meanwhile, the Pareto solution set obtained by the improved algorithm is more widely distributed, avoiding local optima, and the iterative convergence efficiency of the improved algorithm was improved by 81%.

EMI Filter Parameter Design Optimization Based on Improved Particle Swarm Algorithm

2026-05-13

PIER C

Vol. 170, 184-193, 2026

doi:10.2528/PIERC26031102

download: 37

Whole Sub-7 GHz Four-Element Ultra-Wideband MIMO Antenna for IoT Applications Based on Characteristic Mode Theory

Chengzhu Du, Xingyu Liu, Jiaxuan Tian and Zhiyuan Wang

This article describes a four-element ultra-wideband (UWB) Multiple-Input Multiple-Output (MIMO) antenna for the Sub-7 GHz. The antenna element is an elliptical patch slot antenna with a coplanar waveguide (CPW) feed. To make the bandwidth wider, we add step-by-step parasitic stubs based on the results of the Characteristic Mode Analysis (CMA) analysis, which can control multiple modes better. The four-element antenna is connected to a common ground structure with a central cross-shaped isolation stub and also inhibit the propagation of surface waves. It can be used in the range from 1.08 GHz to 8.70 GHz (155.8%), which is fabricated on a low-cost FR4 substrate. In this range, the isolation between antenna elements exceeds 20 dB. The performance of the design is very good. The envelope correlation coefficient (ECC) is less than 0.02, and the diversity gain (DG) is greater than 9.96.

Whole Sub-7 GHz Four-Element Ultra-Wideband MIMO Antenna for IoT Applications Based on Characteristic Mode Theory

2026-05-12

PIER C

Vol. 170, 174-183, 2026

doi:10.2528/PIERC26031002

download: 25

Design of Symmetric Quad Circular Radiator Antenna with Semicircular Bridge and DGS for WLAN, ISM Band and Sub-6 GHz Applications

Prasanth Kumar Jujjarapu, Nallamothu Suneetha, Padavala Akhendra Kumar, Akondi Narayana Kiran and Bokkisam Venkata Sai Sailaja

The proposed symmetric quad circular radiator antenna with a semicircular etched-slot DGS was designed and fabricated on an FR4 substrate of size 50 × 50 × 1.6 mm³. The antenna provides impedance bandwidths of 2.24-2.94 GHz, 3.84-3.98 GHz, and 4.92-5.06 GHz, with resonant frequencies observed at 2.44 GHz (-40.3 dB), 2.86 GHz (-17.9 dB), 3.92 GHz (-14.9 dB), and 4.98 GHz (-10.6 dB). These operating bands make the antenna suitable for WLAN, ISM, and other sub-6 GHz wireless communication systems. The antenna also achieves a realized gain above 5 dB at the operating frequencies, indicating stable radiation characteristics. The diversity performance was evaluated using standard metrics. The ECC remains below 0.5, which lies within the acceptable range for diversity operation. In addition, the diversity gain varies between 9.88 and 10.02 dB, while the channel capacity loss stays below 0.6 bits/s/Hz across the frequency range. A compact symmetric quad circular radiator antenna incorporating a three-segment semi-circular bridge along with a semicircular etched-slot mdefected ground structure (DGS) is presented for multi-band wireless communication applications. These results confirm that the proposed antenna provides reliable radiation and diversity performance for practical wireless communication applications.

Design of Symmetric Quad Circular Radiator Antenna with Semicircular Bridge and DGS for WLAN, ISM Band and Sub-6 GHz Applications

2026-05-12

PIER C

Vol. 170, 162-173, 2026

doi:10.2528/PIERC26032305

download: 22

A Miniaturized Multi-Resonant Wideband PIFA Design for Biomedical Applications

Hanwen Miao, Mengxing Liu, Le Song, Jingjing Shi, Lijia Liu and Jianqing Wang

This paper presents a miniaturized implantable antenna with multi-resonances operating at the Medical Implant Communication Service (MICS) band (402-405) and Industrial, and Medical (ISM) band (433.1-434.8 MHz, 868-868.6 MHz, and 902-928 MHz) for advanced biomedical applications. The proposed antenna is notably compact, occupying a volume of 10 × 10 × 1.27 mm³ (equivalent to 127 mm³). Multi-resonance frequencies are generated by incorporating a shorting pin and a meandered resonator structure. The proposed antenna exhibited wideband characteristics, with bandwidth ratios of 39.5% and 28.8% at 402 and 915 MHz, respectively. Moreover, the performance of the implantable antenna was further validated in different organs within a realistic human body model, such as the heart, stomach, small intestine and colon. The practical performance of the fabricated antenna prototype was validated using a tissue-equivalent liquid phantom. Additionally, to evaluate the transmission performance under real-world scenarios, an on-body antenna matched with the implanted antenna was designed for an in-body to on-body transmission setup. Under the maximum safe input power of 25 μW, link budget analysis demonstrates that data can be transmitted at a rate of 10 Mbps over distances of 9.5 and 12 cm in the MICS and ISM bands, respectively. The simulated and experimental results verified the feasibility of substituting a realistic human model with a homogeneous muscle model in the design of an implantable antenna system and demonstrated a strong potential for diverse implantation scenarios and future biotelemetry applications.

A Miniaturized Multi-resonant Wideband PIFA Design for Biomedical Applications

2026-05-12

PIER C

Vol. 170, 151-161, 2026

doi:10.2528/PIERC26032404

download: 40

A Novel Key-Shaped Miniaturized High-Isolation MIMO Antenna for UWB Applications

Xinyu Liu, Han Lin and Zhonggen Wang

This paper presents a novel key-shaped miniaturized four-port MIMO antenna designed for ultra-wideband (UWB) applications. The proposed antenna consists of four orthogonally and symmetrically arranged key-shaped radiating elements. By integrating semi-circular patches at the edges of rectangular radiators, multiple resonance modes are excited to significantly broaden the impedance bandwidth and optimize matching. To suppress mutual coupling within a compact footprint, an enhanced cross-shaped defected ground structure (DGS) is implemented, which effectively blocks surface wave propagation by utilizing narrow rectangular stubs. Experimental results demonstrate that the antenna achieves a continuous impedance bandwidth from 4.4 to 26 GHz, corresponding to a fractional bandwidth of 141.5%. Throughout the operating band, the port isolation remains better than 28 dB, while the envelope correlation coefficient (ECC) is lower than 0.00013, ensuring excellent diversity performance. Furthermore, the antenna, fabricated on an FR4 substrate with a compact size of 47 × 47 × 1.6 mm³, maintains a radiation efficiency between 67.4% and 92.6%. With its superior bandwidth, high isolation, and exceptionally low correlation, the proposed design offers a robust solution for high-performance UWB communication systems.

A Novel Key-Shaped Miniaturized High-Isolation MIMO Antenna for UWB Applications

2026-05-11

PIER C

Vol. 170, 140-150, 2026

doi:10.2528/PIERC26032002

download: 31

A Flexible Hybrid Rectenna with Frequency-Domain Complementarity for RF Energy Harvesting and WPT

Lei Li, Yang Hu, Yuting Jia, Xiaomeng Wang, Yanting Wang, Enxin Zhao, Shulin Li and Jingchang Nan

A novel flexible hybrid rectenna for simultaneous RF energy harvesting (RF-EH) and dedicated wireless power transfer (WPT) is proposed. The rectenna comprises a notched broadband omnidirectional microstrip antenna (2.8-6.3 GHz with a 4.7 GHz notch) and a 4.7 GHz directional dielectric resonator antenna (DRA) located on the microstrip antenna. At the 4.7 GHz notch band, electromagnetic energy is confined around an L-shaped strip and a split-ring slot of the microstrip antenna, exciting a TM₂₀₁^z resonant mode in the DRA that produces a narrow radiation beam at 4.7 GHz. This enables a frequency-domain complementary operation: ambient energy is harvested across the broadband region for low-power applications, while dedicated power is efficiently received at 4.7 GHz for high-power operation. A broadband rectifier employing a dual-channel impedance matching architecture is further proposed, in which two parallel branches cooperatively extend the rectification bandwidth. Measurements demonstrate that the rectenna achieves efficiencies above 45% across 2.8-6.3 GHz, with a peak efficiency of 57.9%. In addition, the use of Polydimethylsiloxane (PDMS) as the substrate provides high flexibility and excellent conformability. These features make the proposed rectenna well-suited for powering electronics on curved surfaces, compact devices, and curved-surface Internet-of-Things (IoT) nodes, such as robots, drones, in-vehicle applications and industrial robotic arm units, enabling reliable conformal deployment on non-planar equipment and distributed IoT systems.

A Flexible Hybrid Rectenna with Frequency-Domain Complementarity for RF Energy Harvesting and WPT

2026-05-11

PIER C

Vol. 170, 132-139, 2026

doi:10.2528/PIERC26032408

download: 34

Study of a Parallel Second-Order Small Slope Approximation Algorithm for Electromagnetic Scattering from the Rough Surface

Xiao-Yan Zhang, Luqi Wang, Hongwei He and Gang Yu

The second-order small-slope approximation (SSA2) is an analytical approximation method applied to electromagnetic scattering simulations on rough surfaces. However, the conventional serial SSA2 method involves a quadruple integral, and each integration requires a fast Fourier transform (FFT). As a result, the method demands very high memory and suffers from very low computational efficiency. In this paper, a parallel SSA2 method is proposed by combining region decomposition with Message Passing Interface (MPI) programming. The OpenMP technique also adopted to further improve the algorithm's performance. To avoid the frequent communication overhead caused by spectral shifting in traditional parallel FFT methods, the matrix data is carefully allocated, which effectively removes the related communication bottleneck. In addition, by using the separability of the two-dimensional (2-D) FFT, each 2-D FFT is implemented using two sequential one-dimensional (1-D) FFTs. This design limits inter-node communication to a constant upper bound. Numerical results show that when the number of computer nodes reaches 10, the parallel efficiency of the proposed method exceeds 80%, which confirms the effectiveness of the proposed method.

Study of a Parallel Second-Order Small Slope Approximation Algorithm for Electromagnetic Scattering from the Rough Surface

2026-05-10

PIER C

Vol. 170, 121-131, 2026

doi:10.2528/PIERC25121103

download: 43

Noninvasive Brain Tumor Detection Using a Frequency Selective Surface Gain Enhanced Antenna

Sanjeev Sharma, Daljeet Singh, Mariella Särestöniemi, Teemu Myllylä and Rajeev Kumar

This article introduces a microwave system operating in the low-frequency band of 1.6-2.8 GHz, specifically designed for biomedical applications. Tumor detection in the human brain was achieved by monitoring variations in antenna S-parameter response. A high-gain antenna was positioned on the skull's surface, whose gain and directivity are enhanced by backing it with a Frequency Selective Surface (FSS) array. This arrangement effectively channels energy toward human tissues, which facilitates tumor detection. The combined Antenna-FSS structure improved the gain and directivity by 5.3 and 5.1 dB, respectively. Simulations were conducted using a multilayered skull model consisting of the skin, skull, and brain. The experimental validation was done by performing measurements using a near-realistic human brain phantom and by inserting a tumor in the brain area of the fabricated phantom. The study revealed that the measured S-parameters vary by approximately 11.38 dB when a 6 mm × 6 mm tumor is introduced into the brain region. Additionally, S-parameters are analysed by varying shapes, sizes, and locations of tumors within the brain. The study's findings indicate that variations in the characteristics of the S-parameter can be potentially utilized for detecting tumors in the human brain.

Noninvasive Brain Tumor Detection Using a Frequency Selective Surface Gain Enhanced Antenna

2026-05-09

PIER C

Vol. 170, 112-120, 2026

doi:10.2528/PIERC25101701

download: 49

A Novel Compact High-Gain Decagonal Microstrip Antenna for Soil Moisture Sensing via Resonant Frequency Shift

Sahana K and Bharathraj Kumar M

This paper presents the design, fabrication and experimental validation of a novel compact high-gain decagonal microstrip patch antenna designed for noninvasive soil moisture sensing. The antenna utilizes the strong correlation between its dielectric properties and soil moisture content, which directly influences the antenna's reflection coefficient and resonant frequency. The decagonal geometry using a Taconic TLY-5 substrate achieves a high gain of 7 dBi and an excellent radiation efficiency of 96.5% compared to the FR-4 substrate. The prototype antenna fabricated on Taconic TLY- substrate resonates at 2.445 GHz frequency with a measured reflection coefficient of -34.3 dB, validating the high-performance characteristics predicted by full-wave simulations using CST Studio Suite 2018. The sensing capability of the fabricated antenna is carefully tested across sandy, loamy, and clay soils, demonstrating a predictable downward shift in resonant frequency as moisture content increases. A linear regression analysis is performed on the experimental data from sandy, loamy, and clay soils, yielded a high coefficient of determination (R² ≈ 0.9) for all three soil types, establishing a calibration model to accurately convert the resonant frequency shifts into soil moisture values. The obtained sensitivity values for soil moisture detection are 4.76 MHz/% for sandy soil, 5.15 MHz/% for loamy soil and 4.89 MHz/% for clay soil respectively. The compact size, high gain and consistent performance across different soil samples make this proposed antenna a better solution for precision agriculture and environmental monitoring through integration into wireless sensor networks.

A Novel Compact High-Gain Decagonal Microstrip Antenna for Soil Moisture Sensing via Resonant Frequency Shift

2026-05-08

PIER C

Vol. 170, 97-111, 2026

doi:10.2528/PIERC26032307

download: 58

Compact Designs of U-Slot Cut Hexagonal Microstrip Antennas Loaded with Shorting Posts for Circular Polarized Response

Amit A. Deshmukh, Sujay Tawde and Sanjay B. Deshmukh

This paper presents the configurations of U-slot cut hexagonal microstrip antennas loaded with shorting posts, which realize a reduction in the center frequency of axial ratio bandwidth as well as the total substrate thickness. Three configurations employing four, eight, and twelve shorting posts positioned around a hexagonal patch are presented. Shorting posts loading adds to the inductive component in the antenna's input impedance, which yields a reduction in total substrate thickness and frequency. Among three variations, the U-slot cut hexagonal patch employing eight shorting posts yields the optimum result. It achieves axial ratio bandwidth of 2.23%, for 0.033λ_cAR reduction in the substrate thickness and 55 MHz (4.5%) reduction in the center frequency of axial ratio bandwidth. All these results are for marginal reduction in peak broadside gain. Against the U-slot cut hexagonal patch on a reduced substrate thickness, shorting posts loaded antenna achieves higher axial ratio bandwidth with 56 MHz (4.81%) reduction in the center frequency of axial ratio bandwidth. Considering all these results, the proposed design offers a compact circular polarized solution, while employing a resonant U-slot. For the obtained antenna characteristics, the proposed designs can find applications in GPS L5 and L2 bands. Experimental validation for the proposed configurations has been carried out where the measured results show close agreement with simulated ones.

Compact Designs of U-slot Cut Hexagonal Microstrip Antennas Loaded with Shorting Posts for Circular Polarized Response

2026-05-08

PIER C

Vol. 170, 89-96, 2026

doi:10.2528/PIERC25112903

download: 42

Design of a DGS-Loaded Scannable Cosecant2-Shaped Pattern Generating Phased Array Antenna with Improved Cross Polarization

Rajeev Jyoti, Amalendu Patnaik, Gaurav Kumar, Pratik Mevada and Gaurav Ahuja

This manuscript describes the design of a scannable Cosecant² Shaped Pattern Generating Phased Array Antenna (PAA) intended for airborne synthetic aperture radar (SAR). The Cosecant² Shape avoids the requirement of sensitivity time control correction at receiver side. A C-band linear array antenna consisting of 16 elements is designed, analyzed, developed, and characterized. The array antenna is embedded with a U-slot and Defected Ground Structure (DGS) integrated microstrip elements. The introduction of a DGS provides an improvement of 6.5 dB in cross-polarization levels when scanning. Additionally, the null perturbation technique is employed to synthesize the excitation coefficients for the Cosecant²-Shaped pattern, aiming to achieve the minimum current taper ratio. These synthesized coefficients are combined with a progressive phase for beams that can scan within a ±30° angular range. The proposed linear array, along with its excitation and phasing network, has also been developed and characterized in an anechoic chamber.

Design of a DGS-Loaded Scannable Cosecant<sup>2</sup>-Shaped Pattern Generating Phased Array Antenna with Improved Cross Polarization

2026-05-08

PIER C

Vol. 170, 78-88, 2026

doi:10.2528/PIERC26030202

download: 91

Design and Optimization of Four-Coil Magnetic Coupled Resonant Wireless Power Transfer

Sylcolin Rakotonandrasana, Bilal A. Khawaja, Habachi Bilal, Jeannot Velontsoa, Leonide Tongazara, Sébastien Lallechere, Glauco Fontgalland, Fayu Wan and Blaise Ravelo

Magnetic Coupled Resonant (MCR) Wireless Power Transfer (WPT) is typically used for electrical charging, offering high tolerance to misalignment and wider transmission range. However, MCR-WPT is assumed to be a two-port circuit, including transmitter (Tx) and receiver (Rx), and exhibits lower efficiency than conventional inductive power transfer. Various studies have been proposed to increase the 4-coil MCR-WPT efficiency, but further challenges remain due to the turn technology complexity. A relevant and simple design solution is developed in the present paper that enables the optimization of Power Transfer Efficiency (PTE) by minimizing implementation cost. To achieve that goal, the transfer- and resonator-distances, TD and RD, respectively were optimized through theory, both circuit and 3-D electromagnetic (EM) simulations via 3-D modeling and experimentation. The validation PTE results obtained from analytic calculation, simulation and experimentation affirm that the maximum efficiencies of 94.10, 90.15% and 69.35% were obtained at optimal positions around RD = 7.5 mm and TD = 100 mm, respectively. The slight difference of the obtained PTE among theory and simulation with experiment is due to the setup instrument imperfection. The performed study is useful for the WPT charging systems, such as electronic sensors, wearable devices, and communication systems.

Design and Optimization of Four-coil Magnetic Coupled Resonant Wireless Power Transfer

2026-05-08

PIER C

Vol. 170, 66-77, 2026

doi:10.2528/PIERC26032302

download: 61

Multi-Objective Hierarchical Optimization Design of a Variable-Leakage-Flux Reverse-Pole Permanent Magnet Synchronous Motor with Vibration and Noise Suppression

Xiping Liu, Qianli Jia, Hongzhan Hu, Zhangqi Liu, Zhiguo Zhu and Jiao Guo

To address the issue of significant fluctuations in radial electromagnetic forces in variable-leakage-flux reverse-salient-pole permanent magnet synchronous motors (VLF-RSPMs), which make stable operation at high speeds difficult, this paper combines an analysis of existing VLF-RSPMs with a novel optimization method to propose a multi-objective hierarchical optimization design method for VLF-RSPMs, which incorporates vibration and noise suppression. First, the paper analyzes the radial electromagnetic force model, natural frequencies, and electromagnetic vibration model of the VLF-RSPM. Second, based on the optimization objective of vibration and noise suppression, parameters with high sensitivity are optimized first through sensitivity analysis. Subsequently, the modal characteristics, radial electromagnetic forces, noise, and stress of the optimized VLF-RSPM are analyzed in detail. Finally, an experimental VLF-RSPM prototype and a test platform for measuring radial electromagnetic force fluctuations are designed. The results demonstrate that the multi-objective hierarchical optimization design method ensures the operational reliability of the optimized VLF-RSPM, enabling it to meet the requirements for high-speed operation.

Multi-Objective Hierarchical Optimization Design of a Variable-Leakage-Flux Reverse-Pole Permanent Magnet Synchronous Motor with Vibration and Noise Suppression

2026-05-07

PIER C

Vol. 170, 57-65, 2026

doi:10.2528/PIERC26032006

download: 41

Study on Frequency Splitting and Segmented Tracking for High-Performance WPT Under Horizontal Offset

Junjun Li, Jialin Zou, Yao Zou and Zhongqi Li

Wireless power transfer systems suffer from frequency splitting and drift due to horizontal coil offset, which degrade both efficiency and output power. This paper derives a sixth-order equation to calculate resonant frequencies at the maximum efficiency point (Freq-MEP). The frequencies at the maximum power point (Freq-MPP) are determined by differentiating the output power with respect to the operating frequency. Both Freq-MEP and Freq-MPP are shown to vary with horizontal offset. Based on this analysis, a segmented frequency-tracking method is proposed to achieve simultaneous high efficiency and high output power under varying offset conditions. The effectiveness of the developed magnetic resonant WPT system is validated through numerical simulations and experiments.

Study on Frequency Splitting and Segmented Tracking for High-Performance WPT under Horizontal Offset

2026-05-06

PIER C

Vol. 170, 49-56, 2026

doi:10.2528/PIERC26032105

download: 43

Analysis and Optimal Design of a Novel Permanent Magnet Fault-Tolerant Vernier Rim-Driven Motor with Inclined Modulation Tooth

Defeng Zhao, Jingwei Zhu, Yaqian Cai and Anni Wang

To address the trade-off between torque density and power factor in conventional permanent magnet vernier rim-driven motors under material cost constraints, this study proposes a novel permanent magnet fault-tolerant vernier rim-driven motor with an inclined modulation tooth (PMFTVRDM-IMT). Unlike the conventional straight-tooth configuration, the proposed design introduces an inclination angle to the modulation teeth, thereby altering the air-gap permeance distribution pathway while preserving both the permanent magnet volume and overall motor envelope. Through magnetic field harmonic analysis, the underlying mechanism for the synchronous improvement in the torque and power factor was revealed: the inclined modulation tooth structure enhances the effective working harmonics while suppressing the ineffective harmonic components. To further optimize the motor performance, a combined approach of single-parameter scanning and multi-objective optimization was adopted, and the resulting performance metrics, such as the output torque and power factor, were systematically validated using the finite element analysis (FEA). The results indicate that, with modifications only to the modulation tooth structure, the proposed motor design achieves an approximately 15% improvement in the power factor and a 2.5% increase in the torque density, thereby substantiating the feasibility and engineering value of the inclined modulation-tooth topology in mitigating the low power factor issue inherent to vernier machines.

Analysis and Optimal Design of a Novel Permanent Magnet Fault-Tolerant Vernier Rim-Driven Motor with Inclined Modulation Tooth

2026-05-05

PIER C

Vol. 170, 38-48, 2026

doi:10.2528/PIERC25123005

download: 158

A High-Power, Low-Loss Single-Channel X-Band Waveguide Rotary Joint for Radar Systems with Ultra-Low Amplitude and Phase Variation

İsmail Şişman, Emin Polat and Tugba Haykir Ergin

In this study, a high-performance wideband I-type rectangular waveguide rotary joint (RJ) has been meticulously designed, simulated, and experimentally verified for deployment in X-band radar systems operating within the 9-10 GHz frequency range. The proposed RJ achieves superior radio frequency (RF) characteristics, including an insertion loss of less than 0.1 dB and a return loss exceeding -30 dB, making it highly suitable for critical applications that require minimal signal degradation. Unlike conventional rigid waveguide systems that restrict mechanical movement, the developed RJ enables full 360° rotation with negligible variation in both amplitude and phase, thereby ensuring continuous, stable operation in dynamic environments such as mechanically rotating radar platforms. Notably, the design achieves an amplitude and phase wobble (WoW) of only 0.005 dB and a phase fluctuation within ±3.2°, meeting the stringent performance requirements of modern radar and satellite tracking systems. In addition to RF characterization, the rotary joint has been subjected to high-power RF breakdown analysis using particle-in-cell (PIC) simulations to evaluate its resilience under extreme operational stress. High-power robustness was numerically assessed using PIC simulations, indicating stable operation up to 2 kW CW and 30 kW pulsed under the simulated conditions, without breakdown signatures. This performance is further supported by optimized choke structures that minimize discontinuity-related mismatch at the mechanical interface between stationary and rotating sections. The results confirm that the developed rotary joint is not only electrically efficient and mechanically reliable but also capable of sustaining stable RF performance under high-power and rotational conditions, making it a promising candidate for next-generation radar front-ends and high-power satellite communication terminals.

A High-Power, Low-Loss Single-Channel X-Band Waveguide Rotary Joint for Radar Systems with Ultra-Low Amplitude and Phase Variation

2026-05-04

PIER C

Vol. 170, 28-37, 2026

doi:10.2528/PIERC26021205

download: 75

Design and Experiment of Compact Rotary MCR-WPT Coils at MHz Band

Kunming Chen, Yanhong Li, Caiyun Dai, Guo-Qiang Liu, Chao Zhang and Guanchen Li

Aiming to meet the contactless power supply requirements of rotary equipment, this study investigates the coil design and performance of a small resonator for magnetically coupled resonant wireless power transfer (MCR-WPT) systems operating in the MHz band. Based on the series-series (S-S) WPT circuit topology, the influence of coil inductance on the transmission characteristics of the system was analyzed. By combining the inductance calculation formula for planar spiral coils, the geometric parameters of the coil were designed with the objectives of load power (P_RL) > 40 W and transmission efficiency (η_T) > 90%. The rationality of the designed parameters was verified by field-circuit coupled simulation, and the influence laws of the driving frequency and transmission distance on transmission characteristics were also analyzed. The coils were wound according to the designed parameters, and both static and rotary dynamic power transfer experiments were conducted. The simulation results show that the designed coil achieves a transmission efficiency of 94.783% at a transmission distance of 50 mm in the 1 MHz, which meets the preset design objectives. The results of the static experiment and the dynamic rotation experiment show that the overall operating efficiency of the system (η_dc-dc) is 84%. This study demonstrates the feasibility of the proposed coil design method, and the designed small coil can realize high-efficiency and stable wireless power transfer under rotary working conditions. The research findings provide a reference for the coil design and engineering application of rotary MCR-WPT systems in the MHz band and possess practical value for the contactless power supply of sensors in rotary electrical equipment operating in confined spaces.

Design and Experiment of Compact Rotary MCR-WPT Coils at MHz Band

2026-05-04

PIER C

Vol. 170, 15-27, 2026

doi:10.2528/PIERC26030706

download: 62

A Deadbeat Fault-Tolerant Control Strategy for PMSM Demagnetization Faults Based on an Improved Flux Linkage Observer

Yang Zhang, Wancheng Xie, Yang Gao, Jiahao Zhang and Moutao Li

To address issues such as reduced motor output performance and diminished load capacity caused by permanent magnet demagnetization in Permanent Magnet Synchronous Motor (PMSM), a super-twisting algorithm-based fault-tolerant predictive control strategy for demagnetization faults in PMSM is proposed. First, the improved super-twisting non-singular fast terminal sliding mode observer (IST-NFTSMO) is constructed to accurately observe the flux linkage and predict the current at the next moment. Based on the observed values, a deadbeat fault-tolerant predictive control (DFTPC) algorithm is built to compensate for the torque loss due to permanent magnet demagnetization, thereby achieving fault-tolerant control of the system. Second, a sliding mode controller based on a novel reaching law is designed, thereby overcoming the shortcomings of traditional control strategies in PMSM vector control systems, such as poor anti-interference capability and slow response speed. Finally, experimental results demonstrate that after a demagnetization fault occurs in the PMSM, the proposed method effectively improves the fault tolerance capability of the PMSM system while ensuring the dynamic response speed of the control system, thereby endowing the system with enhanced stability and robustness.

A Deadbeat Fault-Tolerant Control Strategy for PMSM Demagnetization Faults Based on an Improved Flux Linkage Observer

2026-05-03

PIER C

Vol. 170, 1-14, 2026

doi:10.2528/PIERC25120601

download: 99

Design Optimization of a Permanent Magnet Biased Fault Current Limiter via Pattern Search for High Efficiency and Reduced Material Use

Tirtha Sankar Daphadar, Tapan Santra and Amalendu Bikash Choudhury

This paper presents a useful design optimization methodology for a permanent-magnet-biased fault current limiter (PMFCL), aiming to achieve good fault current limiting performance with small magnetic materials and their losses. A physics-based magnetic circuit modelling approach is developed to update the nonlinear core saturation and permanent magnet biasing, enabling fast and reliable analysis of candidate designs. Additionally, a weighted multi-objective formulation is adopted to balance fault current mitigation, material volume, and loss minimization. The resulting optimization problem is solved by means of a deterministic pattern search approach, which enables efficient design space exploration without access to gradient information. The optimized configurations are validated using the finite-element simulations, and the robustness of the configurations under practical operating conditions is analyzed. The obtained results show a significant reduction of the magnetic material volume with the optimized PMFCL without compromising and, in certain cases, with an improvement of the function of fault current limiting against a baseline design. The research identifies technical configurations of design that are practical for real-world deployment. The combination of reduced material usage, passive operation, and better energy efficiency means the proposed PMFCL represents a reliable and sustainable solution for better protection of modern power systems, especially in areas where power systems are cost-sensitive and infrastructure-limited.