Although the high-speed train sets are equipped with fully enclosed aluminum alloy car bodies, the end passage areas lack metallic shielding, resulting in a complex electromagnetic environment. This paper takes the Fuxing Intelligent EMU (Electric Multiple Unit) as the research object and uses Maxwell simulation to analyze the low-frequency magnetic field distribution in the end passage under a 50 Hz eddy current field. It also investigates the effects of the 25 kV catenary traction current, rail return current, auxiliary system crossover cable current, and high-voltage system crossover cable current on the electromagnetic environment at the end of the train.

Maglev train has no contact with rail in high-speed operation, which is significantly different from traditional wheel-rail train. A crucial issue of the lightning overvoltage on maglev train is grounding characteristics, however, which has not been fully and thoroughly investigated. In this letter, the multi-path grounding of maglev train is analyzed. A new and advantageous circuit model for researching the grounding characteristics and impacts is demonstrated. And, an experiment of lightning injection has been designed to validate the proposed model.

Abstract To mitigate the failure risk of shipborne navigation RF front ends caused by high-power microwave (HPM) front-door coupling, this study focuses on the BeiDou/GPS L1 band and investigates a coordinated protection scheme combining antenna coupling analysis and a broadband high-power limiter. First, a standard narrowband HPM waveform is established, and a microstrip patch antenna is designed and simulated. The results show that within 1.57-1.58 GHz, the antenna achieves a VSWR below 2 and a peak gain of approximately 6.66 dBi, meeting navigation reception requirements. Under irradiation conditions of 30 kV/m field strength, 10 ns rise time, 100 ns pulse width, and a 1.575 GHz carrier, the induced peak voltage at the antenna port reaches about 620 V, corresponding to an estimated coupled power of 1,900 W, which far exceeds the tolerance of typical shipborne navigation receiver front-end components. To address this, a staged topology featuring a 3 dB hybrid coupler with power splitting and “PIN-diode hard limiting + Schottky-diode soft clamping” is proposed. GC4742-00 and CDF7621-000 are selected to balance high power handling with low-threshold, fast recovery. Simulation results indicate that the insertion loss is below 0.5 dB over 1.4-1.6 GHz; under 1,900 W injection, the output voltage is limited to a peak of 1.84 V and a steady-state level of 1.6 V; harmonic analysis further shows a limited output level better than 5.8 dBm. These results validate the proposed scheme’s effective over-power suppression for shipborne navigation receiver chains while maintaining compatibility with small-signal performance.

Aiming at the problem that insulation fault location in multi-branch cable networks of train DC medium-voltage power supply systems is disturbed by impedance mismatch at the injection end, this paper proposes an impedance matching method based on a resistance-capacitance composite coupling network to suppress false reflections and improve location accuracy. Firstly, the mechanism of multiple false reflections caused by injection-end mismatch is theoretically analyzed, and the expression of reflected waves and their influence on waveform superposition are derived. On this basis, an RC coupling network is designed to achieve effective matching between the measurement end and the cable characteristic impedance (about 97 Omega) within the 8-12 MHz frequency band, suppressing the amplitude of false reflections to less than 2% of the incident wave. Verification through MATLAB R2022b/ANSYS Q3D 2024R2 co-simulation and a 1:8 scaled experimental platform shows that the proposed coupling network reduces the absolute fault location error in a multi-branch network from 6.936 m to 0.188 m, decreases waveform distortion by about 40.8% and lowers the equivalent noise enhancement factor by about 55.2%. This study provides a reliable front-end matching solution for accurate fault location in complex cable networks, with clear value for engineering applications.

PurposeTo support the operational safety and lightning protection design of high-speed maglev railways, this paper quantitatively evaluates how suspension height and operating speed influence lightning susceptibility. It characterizes trends of the critical background electric field with respect to these two variables, tracks the evolution of surface hotspot distributions and identifies dominant attachment locations and their sensitivity.Design/methodology/approachA coupled procedure of “electrostatic field–aerodynamic flow field–scaled assessment” is proposed. The electrostatic model provides surface field-enhancement factors and their spatial distribution, while turbulent-flow simulations characterize near-wall density variations induced by speed. Under a unified leader height, a critical criterion based on a density-scaled breakdown field maps these two fields to a train-wise critical background electric field. Representative regions (nose, roof and bottom or tail) are used to build statistical metrics for hotspot migration and dominance with speed.FindingsIncreasing suspension height weakens electric-field coupling to ground, raises the critical background-field threshold and reduces the relative contribution of bottom and edge regions. At the same suspension height, a rigidly grounded train has a lower critical threshold than an electrically floating one. Within 0–500 km/h, the train-wise threshold decreases slowly with speed. Region-wise, roof-tail and bottom-mid sections show a decreasing trend with speed, while the nose stagnation point increases slightly; over the entire speed range, the dominant region remains the roof-tail section.Originality/valueWithin a unified framework, suspension height and operating speed affect lightning attraction through two distinct channels. Suspension height mainly modifies the threshold and hotspot distribution by changing geometric polarization, whereas speed alters discharge-initiation difficulty through aerodynamically induced density variations. The framework evaluates these effects separately and in combination, explaining the slow variation of the global threshold and the subtle evolution of hotspot locations and providing a physics-based reference for lightning protection design and operational safety assessment of high-speed maglev railway systems.

With the continuous development of urban rail transit, the problem of noise interference caused by the traction harmonic current of urban rail trains to the communication lines along the route has become increasingly prominent. To thoroughly investigate and effectively address this phenomenon, this study utilizes the Matlab/Simulink software platform to build a combined vehicle - network simulation model of the DC traction power supply system and the traction conduction system of a specific type of urban rail train, simulating the train's operating state under acceleration conditions. Based on the established model, the characteristics of the psophometric current at different distances between the train and the power supply station are analyzed, and the variation law of the psophometric current with the distance between the train and the power supply station is obtained. The modeling method proposed in this study can predict the psophometric current of DC - powered urban rail trains. It can also play an important role in the preliminary research stage of different vehicle - network systems in rail transit, providing a powerful simulation analysis tool for the optimal design and performance evaluation of the systems.

This paper presents a quad-band shared-aperture antenna operating in both microwave and millimeter-wave (mmWave) frequency ranges for 5G communication. The antenna integrates an upper-layer frequency-selective surface (FSS) combined with an electromagnetic transparent tri-band filtering antenna in microwave, and a lower-layer substrateintegrated waveguide (SIW) slot array antenna in mmWave operation. A stacked configuration is adopted to achieve quadband shared-aperture functionality. To ensure electromagnetic transparency in mmWave, the low-frequency patch is discretized using bandpass FSS elements and additional FSSs are added to the periphery to expand the electromagnetic transparency area. The mmWave section features a $7 \times 8$ SIW slot array antenna. Simulation results demonstrate that in the microwave bands, the antenna operates at $2.55 \text{GHz}, 3.5 \text{GHz}$, and 4.9 GHz with -10dB impedance bandwidths of $5.2 \%, 5.8 \%$, and 8.6 %, respectively, achieving peak gains of $7.42 \text{dBi}, 8.14 \text{dBi}$, and 8.99 dBi. For mmWave operation at 26 GHz, the antenna exhibits a 4.9 % 10 dB bandwidth and a peak gain of 21.9 dBi.

A novel conical beam antenna with dual band filtering response is proposed by utilizing a metamaterial (MTM). The dual band filtering characteristics are inherently derived from the MTM and achieved through the coaxial feed and the probe coupling. Meanwhile, the conical beam is realized by using the cylindrical probe within the antenna aperture. Notably, the antenna exhibits remarkable compactness: firstly, the transverse size of the MTM is only ~ λ1/7 or ~ λ2/5, where λ1 and λ2 are the free space wavelength of central frequencies of the MTM’s two modes, respectively. Secondly, extra filters are circumvented owing to the filtering performance of the MTM. To substantiate the aforementioned characteristics, the proposed MTM antenna is designed, fabricated, and measured. The measured results show a good agreement with the simulated ones, indicating that the proposed conical beam antenna has two operating bands around 3 GHz and 4.3 GHz, respectively. Additionally, the excellent filtering performance is confirmed by the out-of-band gain suppression level of ~ 30 dB outside the two passbands. It is feasible to use the MTM to develop the dual band filtering antenna with conical radiation.

The reliability of the Medium-Voltage Direct-Current (MVDC) power supply system is crucial for train operation, as it powers control, communication, and other critical onboard systems. Accurately locating insulation faults within this system can significantly reduce troubleshooting difficulty and prevent major operational losses. This study addresses a key challenge in applying Time-Domain Reflectometry (TDR) for fault location in single-core cables of IT systems: the incident-end impedance mismatch caused by the variable characteristic impedance of such cables, which fluctuates with installation distance from a ground plane. First, the mechanism through which this mismatch attenuates the primary fault reflection and generates secondary reflections is theoretically modeled. A resistive-capacitive (RC) coupling network is then designed to achieve bidirectional impedance matching between the test equipment and the cable under test while maintaining essential DC isolation. Simulation and experimental results demonstrate that the proposed network effectively mitigates the mismatch issue. In experiments, it increased the proportion of the primary reflected wave entering the receiver by over 30 percentage points and suppressed the secondary reflection by approximately 80%. These improvements enhance waveform clarity and signal strength, directly leading to more accurate fault location. The proposed solution, validated in a railway context, also holds significant potential for improving insulation fault diagnosis in analogous high-voltage cable applications, such as electric vehicle powertrains.

This work presents the design of a X-band circularly polarized varactor-tuned reflectarray antenna for high-power microwave applications. The antenna unit employs a varactor ($\mathbf{0. 5}$- 2 pF) to achieve 360° phase variation, enabling electrically controlled beam scanning. Circularly polarized radiation is generated through vertically oriented varactor pairs. The design incorporates a composite patch configuration, integrating a splitring resonator coupled to a cross-shaped element through a varactor, and adopts a multilayer architecture optimized for highpower microwave applications. Simulation of an $11 \times 11$ X-band reflectarray demonstrates a maximum gain of 23.21 dBi and 45 % aperture efficiency. The antenna achieves electronic beam scanning from 0° to 40° with an axial ratio below −3 dB and a power-handling capacity of approximately 11 MW under SF6 conditions. The antenna's circular polarization, beam scanning, and high power handling are considered promising for high-power applications.

To address the challenges of system failures and equipment damage caused by excitation inrush currents and overvoltages during no-load energization of high-speed locomotive transformers, a simulation model was developed utilizing PSCAD electromagnetic transient simulation software. This study establishes a no-load switching simulation model for rolling stock transformers within PSCAD, analyzing variations in overvoltage and excitation inrush current amplitudes across different phase angles. Additionally, it compares excitation inrush current amplitudes under varying residual magnetism conditions. A phase-selective control strategy is proposed, integrating the hysteresis characteristics of the transformer core. The model’s accuracy is validated against empirical data obtained from a city train. Employing the Jiles–Atherton hysteresis model, the residual magnetism of the transformer core is quantified. Based on measured data, a relationship curve between switching phase and residual magnetism is fitted, enabling calculation of the optimal closing angle through the phase selection procedure. This approach effectively mitigates overvoltage and excitation inrush current hazards, thereby enhancing the operational safety of the train system.

This study addresses the issues of high energy consumption and low efficiency in conventional electric heating snow-melting systems for railway turnouts. A novel system is proposed that integrates electromagnetic induction heating with traditional electric heating to optimise energy transfer pathways and enhance energy utilisation efficiency. The system enables dynamic adjustment of heating power, thereby supporting adaptive operation under varying environmental conditions. Through theoretical analysis, temperature field simulations, and experimental validation, the energy regulation mechanism and performance characteristics are examined. Results show that, under full snow-cover conditions, the proposed induction heating system reduces snow-melting time by 76.9% compared with traditional electric heating, while achieving a 29% efficiency gain under snow-free conditions. Steady-state temperature rise tests demonstrate close agreement between simulations and measurements: directional heat transfer efficiency improves significantly, with the average rail temperature decreasing by 8.5% and the air temperature in the working area increasing by 15%. Additionally, the system increases the ice-and snow-melting rates by 0.4 and 0.8 times, respectively, while reducing energy consumption by 30-40%. An optimised composite thermal structure further enhances heat utilisation. This study provides both theoretical and practical insights for advancing turnout snow-melting technology and its engineering applications.

A novel switchable frequency selective rasorber (FSR), featuring dual wideband absorption bands and an ultra-wide passband that can be switched to a reflective band, is proposed in this work. This design incorporates a lossy layer and a three-layer reconfigurable frequency selective surface (FSS). An ultra-wideband transmission can be achieved through the lossy layer by means of circular spiral resonators. The switchable function is utilized by a reconfigurable FSS with PIN diodes. Simulation results confirm the FSR's broad absorption from 1.44 to 2.39 GHz (49.6%) and from 5.45 to 6.64 GHz (19.7%). It also achieves an extensive passband with a 1-dB bandwidth of 47.78% (3.17 similar to 5.16 GHz) in the absorption-transmission-absorption (A-T-A) mode, which is the widest transmission band in existing designs. The passband is converted into a reflection band in the absorption-reflection-absorption (A-R-A) mode, showcasing the FSR's switchable characteristics. To validate these simulation outcomes, a prototype measuring 300 x 300 mm is constructed and measured.

A compact quad-band shared-aperture antenna is proposed for wireless communication in this letter. The antenna is designed by integrating a dual-band patch antenna working in lower frequency bands and a dual-band shared-aperture substrate integrated coaxial slot array antenna working in higher frequency bands into a common radiation aperture. The dual-band patch antenna is located above the dual-band shared-aperture antenna, and an air interlayer is introduced in the middle. Through shape and discretization design, the dual-band patch antenna can radiate waves in the lower bands and is electromagnetic transparent to waves in the higher bands. The dual-band shared-aperture antenna can radiate waves in the higher bands into free space and is almost unaffected by the dual-band patch antenna. Quad-band shared-aperture performance is, thus, achieved. The gains of the antenna are 7.4-7.7, 9.8-10.4, 17-18.5, and 18.7-19.5 dBi over working bands 2.55-2.62, 4.74-5.24, 26.5-27.4, and 37.4-38.6 GHz, respectively.

In this paper, a novel E-electric field sensor used for large dynamic range of the transient electric field measurement is designed. The E-electric field sensor includes an asymptotic conical antenna, a signal receiving circuit, an electro-optic modulation circuit and a circuit shielding shell. Firstly, the asymptotic conical antenna is modeled on the simulation software platform, and the better dynamic range is obtained by adjusting the length of the antenna. Its electromagnetic characteristics are simulated. The antenna meets the requirements of omnidirectionality and miniaturization, and it meets the test requirements of E-electric field sensor. Secondly, the sensor signal receiving circuit and electro-optical modulation circuit is designed on the simulation software platform. RC circuit is used to adjust the voltage induced by the antenna in the signal receiving circuit, which can meet the test requirements of high field intensity and large dynamic range. Optic modulation circuit to provide appropriate bias current for subsequent photoelectric conversion is designed. And then, the circuit shielding shell is designed, which is used to protect the back-end circuit, and its size is 10 cm × 10 cm × 10 cm. The simulation results show that the input dynamic range of the sensor is up to 67 dB, the measuring range of this E-electric field sensor is 50 V/m–100 kV/m, and the bandwidth is 10 MHz–1.5 GHz. The E-electric sensor can meet the needs of electromagnetic environment measurement of strong electromagnetic pulse.

Based on the application scenario of high-power electromagnetic environment monitoring, an ultra-wideband bowtie antenna with structure loading and resistance loading is designed. The two vibrators of the bow-tie antenna are printed on both sides of the dielectric substrate. The end of the triangular oscillator of the traditional bow-tie antenna is elliptically loaded first, and then the elliptically loaded oscillator is slits and loaded with resistances. This can not only effectively expand the bandwidth, but also reduce the antenna size. In this paper, the factors that have great influence on antenna bandwidth performance, such as slits position, slits width, resistance value, resistance position, are analyzed and optimized. The optimized antenna radiation characteristics, pattern characteristics and the maximum field intensity are simulated. The simulation results show that the VSWR of the antenna is less than 2 in the 2–21.7 GHz band, the relative bandwidth is up to 166%; the maximum acceptable incident field strength is 113.8 kV/m, which meets the application requirements of high power scenarios; in the working frequency band, the horizontal direction of low frequency band has good omnidirectional, while the horizontal direction pattern of high frequency band has distortion but omnidirectional as a whole; the overall size is 43 mm × 37 mm × 1 mm. Compared with other existing antennas, the antenna designed in this paper has advantages in miniaturization, ultra-wideband and high power handling capacity, which make it suitable for high power electromagnetic environment monitoring applications.

In response to the application requirements for researching array antennas with high-power capacity, high efficiency, and low profile characteristics, a high-power capacity and high efficiency open waveguide array antenna is proposed and designed. The antenna consists of a compact 32-way waveguide power distribution network, a 4×8 rectangular open waveguide unit, and a ceramic sealing radome. By designing the dimensions of the open waveguide and loading E-plane metal grating strip on the surface of the open waveguide, the electric field distribution of the radiation aperture surface is more uniform, and the radiation gain of the unit is improved. The step matching structure is used to achieve the dimensional transformation from the output port of the waveguide power distribution network to the interface of the open waveguide unit cell, while improving the impedance bandwidth of the system. The ceramic radome loaded on the array surface maintains the vacuum state inside the antenna, increasing the power capacity of the antenna. The optimized design of a 32-unit open waveguide array, operating at a center frequency of 4.3GHz, is aimed at meeting the application requirements for C-band high-power array antennas. Simulation results demonstrate that the antenna achieves a gain of 25.54dBi at the center frequency, an aperture efficiency of 93%, and a VSWR of 1.14. Within the frequency range of 4.22 ∼ 4.43GHz, the aperture efficiency remains above 90% while maintaining a VSWR below 1.5. With an overall profile height equivalent to 2 wavelengths at the center frequency, this antenna exhibits exceptional characteristics including high-power capacity (simulated as 192MW in vacuum), high efficiency, and low profile.

In this letter, a quad-band shared-aperture antenna with multibeam in millimeter wave (MMW) is proposed. The antenna is realized by integrating a microwave (MW) electromagnetic transparent tri-band filtering antenna with an MMW multibeam substrate-integrated waveguide (SIW) slot array antenna. By stacking the low-band (LB) and high-band (HB) antennas, the quad-band shared-aperture antenna is achieved. The LB antenna is realized by embedding a dual-band U-slot patch into a perforated patch, and the filtering function is achieved by introducing a stub-loaded resonator into the feeding layer. To achieve electromagnetic transparency in MMW, the LB radiator is discretized by bandpass frequency-selective surface cells. The HB antenna is formed by a 4 x 5 SIW slot array and a 4 x 4 stacked Butler matrix, which achieves four independent beams in MMW. For verification, a prototype is fabricated and measured. In the MW band, the antenna operates well at 2.55 GHz, 3.5 GHz, and 4.9 GHz, with peak gains of 6.8 dBi, 7.7 dBi, and 8.5 dBi, respectively. In the MMW band, the beam directions of the antenna at 26 GHz are +/- 14 degrees and +/- 44 degrees, with peak gains of 15.2 dBi and 14.1 dBi, respectively.