This paper presents a newly developed rod-electrode-type microwave plasma source (MPS), which is mainly composed of a panel mount coaxial connector, a self-made metal adapter with an inlet and outlet of working gas, a quartz tube as a flow path of working gas, and a metal rod-electrode. Microwave energy can be then supplied directly to the working gas from the sharp tip of the metal rod-electrode through the panel mount coaxial connector. To verify the validity of the rod-electrode-type MPS, a reasonable microwave power supply system is built to transmit the microwave power from a magnetron to the panel mount coaxial connector. The experiments demonstrate that the rod-electrode-type MPS can convert by autoignition argon (Ar) into plasma at atmospheric pressure. Moreover, the Ar plasma can be changed to dry air (Air) plasma or nitrogen (N₂) plasma by gradually replacing Ar with Air or N₂. The experimental results show that the rod-electrode-type MPS is potentially an available tool for gas processing at atmospheric pressure.

In this paper, a novel monopole broadband dual-band antenna design for wireless communication systems is proposed, with its fabrication and experimental validation presented. To significantly enhance impedance matching performance, the antenna employs a T-shaped feed slot resonant structure integrated with symmetric L-shaped radiating patches. It covers critical Sub-6 GHz bands (N41/N77/N78/N79) along with Wi-Fi 5 and Wi-Fi 6 spectrums. Notably, the N41 band, as a core 5G frequency band, possesses advantages such as wide bandwidth, strong penetration capability, and flexible deployment, rendering it ideal for urban coverage and high-speed transmission. Experimental results demonstrate that the antenna achieves a -10 dB impedance bandwidth spanning 2.43-2.72 GHz and 3.31-7.32 GHz, with a peak gain of 5.48 dB under omnidirectional radiation characteristics. Its compact design is suitable for miniaturized terminal devices, exhibiting high practical value in 5G Sub-6 GHz and multi-band wireless communication applications.

The permanent magnet brushed DC motor (PMDCM) features a simple structure and reliable performance, making it widely used in home appliances and automotive applications. To further optimize the output torque quality of the PMDCM, this paper proposes a concave-slot Halbach array magnet ring (CSHAMR) structure. First, a finite element model was established to analyze the electromagnetic characteristics of the motor. By comparing with the traditional Halbach array magnetic ring (THAMR), the superiority of the proposed structure for application in brushed motors was verified. Secondly, by defining the magnitude of the no-load back electromotive force (EMF) generated by a single-sided conductor within the interval ``γ'' , the optimization level of the CSHAMR structure for commutation performance was evaluated. The influence of concave slot parameters on motor commutation performance under different values was analyzed. Finally, a parametric model of the CSHAMR was established, and multi-objective optimization of the motor was performed based on the particle swarm optimization (PSO) algorithm. The results demonstrate that CSHAMR can effectively reduce torque ripple and cogging torque in PMDCM motors while improving motor commutation performance.

Highly-miniaturized MIMO antennas are very much desired for 5G-and-beyond hand-held devices as well as miniaturized stationary devices for WSN and IoT applications. In this paper, two compact two-port printed MIMO arrays, measuring 28 × 14 × 0.8 mm³ each, with and without isolation enhancement, are proposed. These arrays have nearly omni-directional radiation patterns over an extended operational bandwidth. The proposed designs feature an extended set of control parameters by which the desired performance could be achieved without compromising space and weight requirements or accuracy. They were fine tuned to provide an operational bandwidth about 4 GHz with relatively low starting frequencies of 2.7 and 3.3 GHz, respectively, allowing simultaneous WiFi, WiMax, 5G operation with a moderate gain and very high efficiency. Prototypes are manufactured and examined for impedance bandwidth, isolation, diversity, and radiation properties showing very good agreement with simulation results.

This study presents a structure design methodology to analyze the operational efficiency of a flux switching permanent magnet machine utilizing non-oriented electrical steel materials. First, iron losses of non-oriented electrical steel materials assembled by bonding and welding stacking methods ware tested, and the comparison results demonstrated that the bonded stator core exhibited lower iron losses than the welded stator counterpart. Then, the proposed non-oriented electrical steel material 35SW360 was implemented in the straighted-rotor core of flux switching permanent magnet machine, and the simulation results shown that both the amplitudes and harmonics of induced electromotive force with 35SW360 was almost identical to the standard non-oriented electrical steel material DW360_50. Finally, prototype flux switching permanent magnet machine with straighted-rotor and skewed-rotor including above two non-oriented electrical steel materials was manufactured and tested. Both the simulation analysis and hardware test results revealed that the flux switching permanent magnet machine with skewed-rotor achieved higher efficiency than the straighted-rotor design. Consequently, the proposed non-oriented electrical steel material 35SW360 and skewed-rotor design illustrate a potential solution for efficiency improvement of flux switching permanent magnet machine.

The burgeoning reliance on electronic devices in sectors such as aerospace systems and consumer electronics necessitates robust electromagnetic interference (EMI) shielding. Current challenges often involve balancing material performance with sustainability and cost-effectiveness. This study addresses these needs by exploring the use of recycled carbon fiber (rCF) in acrylonitrile butadiene styrene (ABS) composites for enhanced EMI shielding, contributing to more sustainable material development. We investigated the impact of different rCF treatments (untreated, chemically treated, and chemically-mechanically treated) on the mechanical properties (tensile strength, stiffness, flexibility) and EMI shielding effectiveness of these composites. Furthermore, the role of electron beam (EB) irradiation at 200 kGy in creating cross-linked structures to boost conductivity and shielding performance was thoroughly examined. Fabricated via melt compounding, the composites' electrical conductivity and EMI shielding capabilities were the main focus. Results show that the EB-irradiated composite with 30 wt.% chemically treated rCF achieved a peak electrical conductivity of 1.34 × 10^-8 S/m and an impressive shielding effectiveness of 46.13 dB. These findings offer crucial insights for developing high-performance, cost-efficient, and potentially sustainable rCF-filled ABS composites for advanced EMI shielding applications.

This paper presents the design of an absorptive metasurface suitable for complex-shaped targets, achieving precise control over electromagnetic waves, which has been experimentally validated. The metasurface, with a design thickness of only 0.27 mm, maintains sufficient absorption properties under appropriate curvature conditions to ensure the stealth characteristics of the coated target. Through simulation and experimental validation, this study demonstrates the metasurface's strong resonance characteristics near 11.26 GHz and a reduction of approximately 3 dB in far-field radar cross section (RCS) simulation. The experimental test results are almost consistent with the simulation results, confirming the metasurface's effectiveness in reducing the RCS of actual complex models. The research findings provide strong technical support for the radar stealth research of targets.

Quadrature 3-dB impedance-transforming transdirectional (TRD) couplers based on double-shielded coupled lines are analyzed and synthesized; design relationships are also presented. To verify proposed concept two couplers implemented with high-permittivity (higher than 10) dielectrics are designed, fabricated, and measured. The first TRD coupler features a suspended ceramic bar, and the second one features a meandering layout of the upper line on a high-permittivity dielectric overlay. Comparison of the proposed solutions with known ones shows that novel coupler designs have advantages in small dimensions and an extended bandwidth of operating frequency (about 1.5-2 times). The simulated results are in good agreement with the measurement data.

Spherical harmonics are classical analysis tools in many science and engineering domains. For analyzing the electromagnetic fields of antennas in the frequency domain, the mostly used formulation is the one proposed by Hansen. This article proposes an alternative solution, relying on spin spherical harmonics. On a sphere, the tangential components of the electric and magnetic fields are represented by means of harmonics of spin ±1. Then new closed-form relations are established between the spin spherical harmonics and the ones formulated by Hansen. A sampling theorem and fast transforms that are consistent with spin spherical harmonics are used. The radiations of spin spherical harmonics of order 1 are related to elementary dipoles and Huygens sources in circular polarization. Finally, numerical experiments are performed with a horn antenna and a GNSS antenna installed on an aircraft. They show that a very large radiating system with a band-limit of 2048 can be efficiently analyzed by means of fast spin spherical harmonic transforms, with a computation time of 2 minutes, approximately.

The misalignment between the transmitter and receiver coils in the wireless power transfer WPT systems causes a reduction in the power transfer efficiency (PTE). This manuscript presents a numerical and experimental study of a WPT with different sequences that compensate for the misalignment effects of WPT systems. Circular loops were used for the transmitter's source coil and the receiver's load coil. Then, a magnetic resonator coil has been added to the transmitter and receiver circular loops. The transmitter coil (Tx) has 4 turns and is connected to a 67 pF capacitor, and the receiver coil (Rx) has 14 turns and is connected to a 9 pF capacitor, which resonates at 13 MHz. The planner 5 × 5 spiral rings array of the metamaterial (MTM) was designed. The MTM unit cell has 5 turns and is loaded with an external 100 pF capacitor. Four scenarios are studied. The first one is the Tx and Rx coils in misalignment without MTMs, and the second one is by inserting the MTM plate in the middle space. Then, double plates are used in the middle, and finally, MTM plates are located behind the coils directly. The transmission coefficient S₂₁ is enhanced by -7 dB when the MTM plate is placed in the middle space between coils. Adding another layer of MTM results in an increase in coupling between coils and enhances the S₂₁ by -1 dB from the previous value. The PTE is improved from 32% to 63% in the instance of misalignment when MTM plates are behind coils. Finally, measurements are achieved and show acceptable agreement with the simulated results. This work could be helpful in biomedical implants where the locations of Tx and Rx coils are frequently changed.

This paper presents a numerical iterative approach to synthesizing multiband filtering functions that can realize equi-ripple in-band responses and enforce the same return loss (RL) level across all passbands. By iteratively updating the reflection zeros (RZs) and some additional transmission zeros (TZs), the multiband filtering function can be constructed to give an equi-ripple characteristic and ensure the same RL levels in all passbands. The advantages of the proposed method include that equal RL level in all passbands can be enforced, and the numerical stability is improved over existing methods. The proposed method can be used to synthesize symmetric or asymmetric multiband filter (MBF) responses with an arbitrary number of passbands. Two synthesis examples are provided. The first example is a tri-band filter (TBF) with an RL level of 23 dB. Its passband frequency ranges are (-1, -0.7), (-0.15, 0.15), (0.7, 1) rad/s, in the normalized frequency domain, and the numbers of poles in the three passbands are 5, 4, and 5, respectively. In the second example, a dual-band waveguide filter (DBF) with four poles in each passband is synthesized and designed. The frequency ranges of the two passbands are (11.8, 11.95), (12.085, 12.2) GHz. Both simulated and measured RL levels of the filter are 22 dB. The measured insertion loss 0.73 dB in the lower passband and 0.75 dB in the upper passband. The simulated and measured results are in excellent agreement with the theoretical response, thus verifying the proposed synthesis method.

Non-embedded uncertainty analysis methods are widely used in the field of electromagnetic compatibility (EMC). Their essence is to construct a surrogate model to simulate the actual electromagnetic simulation process and obtain the desired uncertainty simulation results through exhaustive sampling. However, when performing complex electromagnetic compatibility simulations, non-embedded uncertainty analysis methods face an inherent problem. This problem arises from the excessive number of deterministic simulations, which leads to computational inefficiency. In this paper, an active sampling strategy based on Bayesian optimization is proposed. By selecting the locations of deterministic simulation sampling points in a more reasonable manner, the overall number of sampling points required for the uncertainty simulation can be minimized, thereby improving the computational efficiency. Finally, the effectiveness of the sampling strategy proposed in this paper was verified using a typical parallel cable crosstalk example and a lightning electromagnetic pulse electromagnetic interference simulation example.

This paper presents a numerical approach for solving the magnetic diffusion equation using structure-preserving discretization methods, like Discrete Exterior Calculus (DEC) and Finite Element Exterior Calculus (FEEC). A detailed derivation of the DEC operators is provided, also their geometric foundation and relevance for discretizing differential forms on meshes. Furthermore, the paper includes an explicit introduction to the finite element exterior calculus framework, with a concise overview of the underlying functional spaces. The proposed formulations aim to preserve the topological and metric structure inherent in Maxwell's equation system. Numerical examples illustrate the stability and convergence of both methods, while also comparing their treatment of boundary conditions and discrete Hodge star construction which makes DEC and FEEC solvers spurious free and efficient useful for complex geometries.

In this paper, a highly compact half mode substrate integrated waveguide (HMSIW)-based self-quadplexing antenna is proposed, employing four quarter-mode SIW (QMSIW) radiating elements integrated with longitudinal slots. The antenna operates at four closely spaced resonant frequencies 3.68 GHz, 3.83 GHz, 4.04 GHz, and 4.17 GHz achieved by precisely tuning the slot dimensions. A minimum port isolation of 26 dB is maintained between any two ports, ensuring minimal mutual coupling. The proposed design exhibits a compact footprint of only 0.05λ₀², where λ₀ is the free-space wavelength at the lowest resonant frequency. The simulated and measured gains exceed 5.5 dBi across all four bands, with a radiation efficiency of approximately 85%. Owing to its compact size, high isolation, and efficient radiation performance, the proposed antenna is well-suited for the upper S-band (3.1-3.9 GHz) and lower C-band (4.0-4.2 GHz) which are widely allocated for fixed-satellite service (FSS) communications applications.

This study introduces a compact four-port UWB MIMO antenna featuring dual-band rejection capabilities aimed at suppressing interference from coexisting wireless services, specifically WiMAX at 3.5 GHz and WLAN at 5.5 GHz. The antenna employs an inverted C-slot etched into the radiator to achieve the WiMAX notch, while EBG structures are integrated to enable suppression of the WLAN band at 5.5 GHz. Fabricated on a low-cost FR4 substrate with dimensions 52 × 52 × 1.5 mm³ (ε_r = 4.5), the proposed design achieves high port isolation exceeding 15 dB across the 3.1-10.6 GHz UWB range. Simulated results show an operational bandwidth from 3 to 11 GHz, extending beyond 12 GHz in measurements, without the need for additional filters or decoupling structures. The antenna exhibits quasi-omnidirectional radiation patterns with a peak gain of 7.2 dBi and significant gain suppression at the notch frequencies (-1.5 dBi at 3.5 GHz and -1.2 dBi at 5.5 GHz). It maintains a VSWR below 2 across the UWB and achieves radiation efficiency above 90% outside the notched bands. The envelope correlation coefficient remains below 0.005, enabling a high diversity gain approaching 10 dB. The EBG structures effectively reduce mutual coupling, allowing a compact element spacing of just 2 mm (approximately λ/12.5 at 12 GHz). Both simulation and measurement results validate the proposed design's suitability for mitigating co-channel interference in UWB-MIMO applications, including satellite communications in the S/C/X bands and high-speed wireless systems.

This paper presents the design and implementation of a compact 4-port antenna element with high isolation for 5G sub-6 GHz applications. Four V-shaped patch elements are arranged orthogonally on a 1.58 mm thick FR4 substrate to mitigate mutual coupling in the proposed structure. A defected ground plane method is utilized to further enhance and optimize the characteristics of the antenna at the operating frequency. The antenna operates in the 3.15-4.1 GHz frequency range, providing a 950 MHz impedance bandwidth at -10 dB, making it suitable for mobile terminals within the 5G sub-6 GHz band. The orthogonal polarization results in isolation levels below -18.1 dB, making the antenna ideal for 5G handset communications. This high isolation is reflected in an envelope correlation coefficient (ECC) of less than 0.04, while the diversity performance is verified by a total active reflection coefficient (TARC) of less than -10 dB. The channel capacity loss (CCL) of the four-port antenna element is calculated to be below 0.1 bps/Hz at 3.5 GHz. The MIMO antenna was fabricated, and its measured performance closely matches the simulated results, confirming that the proposed MIMO antenna is well-suited for future sub-6 GHz cellular communications.

We present an eight-page in-depth study of a single-layer broadband reflectarray antenna operating over the 8 GHz to 12 GHz X-band. The array employs a dual-ring hex-slit unit cell and a physics-informed deep-learning (DL) surrogate model that reduces geometry optimisation time by ×120 compared with brute-force sweeps. The 30 cm × 30 cm prototype comprises 273 passive elements, delivers a 530° reflection-phase span, 27 dB peak gain, 56% aperture efficiency and 34.6 dB cross-polar discrimination. A residual network trained on 5000 HFSS datapoints predicts reflection phase with 0.9° MAE, whereas its inverse sibling outputs element radii in 10 ms. CST full-wave simulations and a preliminary S-parameter measurement corroborate the synthesis accuracy to within 0.25 dB. Comprehensive parametric, angular-stability and computational analyses provide guidance for extending DL-assisted reflectarrays to higher frequencies and reconfigurable architectures.

Severe pneumonia poses a significant threat to public health. Delayed diagnosis is a core challenge in treatment. This study uses two rapid, low-cost spectroscopic fingerprinting techniques - Raman spectroscopy and attenuated total reflectance Fourier transform infrared (ATR-FTIR) absorption spectroscopy - to analyze biofluids such as blood and bronchoalveolar lavage fluid (BALF). In contrast to our earlier work which combined infrared spectra with clinical biochemical test results, this paper focuses solely on the spectral data to validate a fast and label-free diagnostic method. We used a spectral transformer network (STNetwork) to perform AI-based classification of severe pneumonia from the spectral fingerprints of blood and BALF. While both modalities are effective, FTIR spectroscopy exhibits superior diagnostic precision (97.78% test accuracy) and stability (SD < 0.0139) for blood samples. BALF offers a unique window into the local lung microenvironment, and both metabolomic analysis and spectral fingerprint classification were performed. The classification results for BALF Raman spectra (enhanced with surface-enhanced Raman spectroscopy) gave a training accuracy of 96.71%±1.86% and a testing accuracy of 90.62%±3.95%, better than the classification results for BALF FTIR spectra. The present study provides a reliable technical foundation for developing rapid and high-accuracy screening solutions for severe pneumonia.

This paper introduces a deep learning assisted sensor for material classification based on two adjacent split-ring resonators unit cell sensor. This sensor operates in the frequency range from 7 GHz to 8 GHz. The sensor is designed to differentiate between different dielectric materials based on their reflection and transmission properties. A dielectric container is used to hold different samples. Reflection and transmission coefficients for different materials are used for classification between different dielectric materials. These materials are also characterized by using Dielectric Assessment Kite (DAK) for verification with the proposed method. The Dual Split Ring Resonator (DSRR) unit cell enhanced resonance characteristics facilitate the classification process for distinguishing different dielectric materials. The measured results of the proposed sensor exhibit a broad detection range, accurately identifying various samples based on their unique resonant frequency responses. The proposed sensor finds utility in industrial applications, identifying and categorizing various different dielectric materials. In addition, the proposed design is used to measure a mixture of two different materials with different volume mixing ratios. The measured samples are used to train a convolution neural network to predict the mixing ratio from the measured S-parameters. The combination of this sensor and the trained model is found to be an efficient tool that determines the mixing ratios of different samples in a fast way. This concept can also be useful to be applied on other types of sensors and other sensing parameters.

This paper proposes a novel and compact conformal fork-shaped microstrip patch antenna operating at 10.2 GHz for X-band wireless communications. It features a fork shaped unique radiating structure optimized for impedance matching, bandwidth enhancement, and compactness. Parametric studies confirmed optimal performance at feed width 3.5 mm and thickness 0.4 mm. An operating band from 9.31 to 11.88 GHz for S₁₁ <= -10 dB with a bandwidth of 2.57 GHz is attained. It exhibits a peak gain of 5.6 dB at 10.2 GHz with radiation efficiency 88.29%. To validate its suitability for flexible and modern wireless applications, conformal models are developed, and their performance is analyzed for metrics like operating band, radiation patterns, peak gain, and radiation efficiency. It is prototyped on a Rogers RT Duroid 5880 substrate, and experimental validation demonstrates strong correlation between simulated and measured characteristics.