A compact yet simple, printed monopole design targeted at providing multiband operation in the 2.4/5/6 GHz Wi-Fi 8 (2400-2484/5150-7125 MHz) bands and also the 5G new radio (NR79) (4.4-5.0 GHz) band and 6G upper mid-band in the 7.125-8.4 GHz range is demonstrated. The antenna is composed of longer and shorter radiating arms, as well as a matching stub that protrudes from the longer arm around the antenna port and extends toward the shorter arm. The two arms and the stub are all printed on a low-cost single-layer substrate. Four resonant modes of the antenna are excited, with the lower mode covering the 2.4 GHz band and the three upper modes forming a wide 7.4-dB return-loss bandwidth of about 4.3-8.6 GHz, covering the 5G NR79 band, 5/6 GHz Wi-Fi bands, and 6G upper mid-band. Additionally, the design can be fed by a commercially available coaxial cable, allowing the antenna to have considerable flexibility in installation within wireless devices.

This study presents a method which improves the accuracy of Preisach model that is able to reproduce the magnetic response of ferromagnetic material to change of magnetic fields, especially at higher frequency. The approach consists in extending an existing model and uses mathematical tools like combining a closed-form Everett function for hysteresis modeling with the Monte Carlo integration method to approximate the Preisach function, making calculations faster and more reliable. To find the best settings for the model, two optimization techniques are used: genetic algorithms (GA) and artificial bee colony (ABC). The model is tested by comparing its predictions to real-world experimental data, and it shows excellent accuracy and efficiency. Between the two techniques, GA performs better in terms of precision and reliability, making it a good choice for solving complex problems in modeling magnetic behavior.

The use of electromagnetic fields to preserve food items by inactivating microorganisms is gaining increasing popularity. Among the different electromagnetic treatments used for fruit juice preservation, Pulsed Electric Field treatment is a prominent method. However, in the Pulsed Electric Field treatment chambers used today, the current flow and energy dissipation within the juice are very high. These high currents cause unwanted electrochemical reactions inside the juice and also raise its temperature. This work introduces a method to prevent these by reducing the current flow with the help of an air gap inside the Pulsed Electric Field treatment chamber. A mathematical model of the proposed system was created, and the reduced current values were calculated. Simulations using COMSOL Multiphysics software were conducted to analyse the electric field distribution and the increase in juice temperature. The optimum value of air gap that can be provided inside the chamber without the risk of electrical breakdown was determined through simulations of electric field intensities and later confirmed through experiments. The effectiveness of the proposed system in inactivating microbes was assessed through microbiological experiments using Escherichia coli bacteria in watermelon juice. According to the experimental results, the proposed system successfully achieved bacterial inactivation with a low current value and without any measurable increase in juice temperature. To the best of our knowledge, there are very limited studies addressing the reduction of current flow within a Pulsed Electric Field treatment chamber through the incorporation of air gaps. In the future, this novel method for preserving fruit juices could prove highly beneficial to the food processing industry.

Long-range wireless power transfer (WPT) is difficult with unguided radio waves or magnetic coupling. In this work, a plasma-assisted quasi-parallel planar waveguiding medium is proposed for overcoming the transmission range issues. Method: A dielectric layer sitting on a conductive object or grid was used as a medium for WPT. At the transmitting end, a plasma ball shielded with a spark-gap activated hemispheric metal cap was used to ionize the air in the space, thereby forming the top cladding layer of the quasi parallel-plate waveguide. At the receiving end, the transmitted power was coupled out of the waveguide over the entire ultrasonic spectrum using Avramenko diode configurations. A Kretschmann-like configuration was used at both ends for conversion between a plasmonic current and the surface waves. Results: In the proposed experimental setups, the transmitted power was successfully harvested over a frequency range from near DC to 230 MHz, with the ratio of the received power to the transmitted power significantly surpassing the value predicted by the Friis' two-ray ground reflection model. Conclusion: WPT based on surface waves is technically feasible with the help of Kretschmann-like configurations.

We present a microstrip dual-frequency rectifier circuit, which includes a voltage-doubling rectifier circuit, a sector-shaped dual-frequency harmonic suppression network, and a Π-shaped dual-frequency impedance matching network. Four fan-shaped microstrip stubs were utilized to suppress the fundamental and higher-order harmonics in the two frequency bands. A microstrip line is employed to form a Π-shaped impedance matching network to achieve impedance matching in both frequency bands. The measured results show that at input power of 15 dBm, the rectification efficiencies are 50% and 43% at frequencies of 2.45 GHz and 5.80 GHz, respectively. This dual-frequency rectifier circuit can be applied to scenarios such as powering passive RFID tags and IoT sensors.

The problem of Radio Frequency (RF) jamming is a significant threat to any current wireless communication network, since a low-power source may seriously diminish or disrupt legitimate conditions of a transmission. Traditional methods of detection based generally on a fixed threshold or packet-level cues cannot be effectively sustained in the presence of adaptive and reactive jamming behavior as observed in real-world deployments. This paper introduces a system of RF signal monitoring and threat detection integrating frequency-domain feature extraction, supervised machine learning, and statistical signal characterization. Both time-domain (such as Received Signal Strength Indicator (RSSI) and Signal to Interference plus Noise Ratio (SINR) metrics and spectral quantities calculated with the Fast Fourier Transform (FFT) are being used to capture both temporary and persistent interference patterns. The hybrid ensemble approach in the form of Random Forest and XGBoost classifiers is implemented to achieve a balance among robustness, interpretability, and classification performance of various jammer types. Empirical testing with actual RF data demonstrates that the suggested method has an initial detection rate of 98 percent, and its performance does not degrade in the low signal-to-noise ratio regime. These findings imply that the combination of lightweight spectral analysis and ensemble learning is a feasible and scalable solution to real-time RF threat detection in dynamic wireless systems.

To enhance communication performance in mountainous environments, unmanned aerial vehicle (UAV)-assisted communication systems have emerged as a mainstream solution. Channel modeling for UAV-assisted communication is a critical research focus, confronting prominent challenges, including balancing computational efficiency and modeling accuracy. This paper proposes a hybrid modeling approach that combines ray tracing (RT) and the variable-step Fourier transform-based Split-Step Parabolic Equation (V-FSSPE) to address the issue. The proposed method fully leverages the strengths of RT in accurately calculating direct, reflected, and diffracted propagation paths, as well as the advantages of V-FSSPE in efficiently modeling long-distance and large-scale areas. A hierarchical model suitable for low-altitude UAV communication is thereby established. Simulation results demonstrate that, compared with traditional modeling methods, the proposed method in this study effectively balances accuracy and efficiency in terrain-dominated air-to-ground channels, making it suitable for millimeter wave (mmWave) communication and emergency communication network planning in terrain-dominated propagation environments. Since factors such as vegetation and atmospheric effects have not yet been incorporated, practical deployment requires case-specific corrections based on the actual environment. Nonetheless, this framework is expected to provide important theoretical references and foundational support for the design and optimization of communication systems in related fields.

Interrupted Sampling Repeater Jamming (ISRJ) is a typical intra-pulse coherent deceptive interference that poses a serious threat to radar target detection and tracking performance. This paper proposes an anti-jamming method that integrates a dual-modulated SSFA-MCPC waveform with a segmented mismatched filtering scheme. Based on the multi-carrier phase-coded (MCPC) signal, we apply random sub-pulse frequency agility and chaotic time-domain phase coding to design the SSFA-MCPC waveform. This design enhances the distinction between the radar signal and interference and improves the mutual masking among sub-pulses. To counter ISRJ, a segmented mismatched filtering algorithm is proposed. Specifically, a bank of sub-pulse matched filters is constructed to perform segmented pulse compression on the received echoes, and the Otsu algorithm is employed to adaptively identify jammed sub-pulses. Finally, a reconstructed mismatched filter is applied to suppress interference. Simulation results demonstrate that the proposed method does not rely on prior knowledge of the jamming parameters and can effectively suppress ISRJ under three different forwarding modes. Compared with existing methods, the proposed approach has lower computational complexity and shows strong potential for practical engineering applications.

The Fifth-Generation (5G) radio network consists of two spectrums: one millimeter-wave band (24-40 GHz) and the other below 6 GHz, which is also popularised as sub-6 GHz band. The spectrum of a sub-6 GHz radio network may be divided into three bands, i.e., low-band (below 1 GHz), mid-band (1-2.6 GHz), and upper mid-band (3.5-6 GHz). The low-band provides a good network coverage, and the mid-band offers a balance between coverage and capacity, whereas the high-band provides the super data capacity and speed. The service providers use combinations of different bands from these three segments of sub-6 GHz spectrum to deliver smooth 5G services. In this work, a novel design of a multiband Double Sided Printed Dipole Antenna (DSPDA) system is proposed that operates at least at one band in each segment of the sub-6 GHz spectrum. The design consists of two DSPDAs, a symmetric one and an asymmetric one, fed in series by a common line in a tree-like structure. The multiple bands are obtained by having fundamental resonant frequencies and their harmonics. All bands are predictable by the design equations. It also provides the flexibility of choosing any band of operation. The antenna is experimentally verified.

This comment addresses errors in the explicit expressions of the Ω matrix presented by Blankenship et al. (2025) [1]. We show that sign inconsistencies in the original formulation can lead to non-physical results, including the violation of energy conservation in passive lossless environments. We provide corrected formulas for the affected matrix entries and numerically verify that the corrected formulation restores physical consistency, with the total energy conserved to the displayed precision in the lossless benchmark.

This research paper presents a low-profile ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with enhanced isolation and wideband performance, employing polyimide as the substrate. The suggested configuration consists of two symmetric radiating elements incorporating rectangular and circular slots within a compact footprint of 36 × 21.1 × 0.1 mm³. To effectively suppress mutual coupling, a slot-based metamaterial-inspired defected ground structure (DGS) with a meandered profile is introduced between the antenna elements. In addition, inverted U-shaped stubs and optimally placed slots are integrated to form a stub-loaded decoupling network, further improving inter-element isolation across the UWB spectrum. The antenna exhibits resonant modes at 4.16 GHz (WLAN), 5.49 GHz (IoT and smart home applications), 7.54 GHz (satellite and point-to-point communications), and 11.61 GHz (high-resolution imaging and sensing), covering the 4-12 GHz frequency range. Predicted and tested outcomes present good agreement, with key MIMO performance parameters achieving Channel Capacity Loss (CCL) below 0.4 bits/s/Hz, diversity gain (DG) above 9.9 dB, Envelope Correlation Coefficient (ECC) below 0.005, and Total Active Reflection Coefficient (TARC) less than -10 dB. Owing to its compact size, wideband operation, and high isolation characteristics, the suggested antenna is a strong candidate for wireless area networks and emerging IoT-based sensing applications.

A direct-through three-level inverter topology based on center-tap inductance and its complex vector control strategy are proposed. This topology structurally avoids the direct short-circuit problem of the DC side capacitor, eliminates the need to set a dead zone in the drive signal, and eliminates the low-order harmonics introduced by the dead zone. For this direct-through inverter, the corresponding complex vector control strategy is studied. By establishing a full-frequency domain model of the system, the fundamental cause of the coupling of DQ-axis currents in the synchronous rotating coordinate system was analyzed. To address the issue of poor dynamic response caused by coupling, a complex coefficient controller was designed. By introducing imaginary parts into the controller parameters, the additional poles introduced by coordinate transformation were offset, achieving decoupling control of active and reactive currents.Simulation and experimental results show that, compared with the traditional real-coefficient PI controller, the proposed complex vector control strategy can effectively reduce the coupling degree of DQ-axis current, improve the dynamic performance of the system, and verify the correctness and effectiveness of the proposed topology and control method. This inverter topology features both high reliability and excellent output performance without increasing the number of power switch devices.

This paper proposes a dual-band class-F^-1 high-efficiency power amplifier with an integrated structure for harmonic suppression and fundamental matching. The fundamental matching network employed a dual-frequency coupler with open branches. This structure is partially reused for third-harmonic control by leveraging two open branches and two branch lines. By adjusting the characteristic impedance of the quarter-wavelength transmission line, the third-harmonic impedance is adjusted to a short circuit at both fundamental frequencies at the drain of the power amplifier. The second-harmonic control network consists of a quarter-wavelength open stub and a drain bias line loaded with a double spiral defected ground structure (DGS), which controls the second-harmonic impedance to an open circuit state at the drain, satisfying the class F^-1 harmonic conditions. A dual-band high-efficiency class F^-1 power amplifier operating at 2.6 GHz/3.4 GHz is designed and fabricated. The measured results show drain efficiencies of 73.5% and 74.3% at 2.6 GHz/3.4 GHz, with output power exceeding 40 dBm and gain above 10 dB.

Wide-stopband plasmonic filters are essential components in compact mid-infrared (MIR) photonic systems. This work proposes a geometrically tunable wide-stopband plasmonic filter based on a metal-insulator-metal (MIM) waveguide with dual resonator cavities. The optical response is numerically investigated using the two-dimensional finite-difference time-domain (2D FDTD) method. The influence of the resonator height H₂ and the inter-cavity distance D on the stopband characteristics is analyzed. The symmetric dual-cavity configuration enables effective control of the stopband bandwidth and central wavelength. The design achieves a significantly broadened stopband while maintaining compactness and high transmission selectivity, making it a promising candidate for integration into mid-infrared photonic and sensing systems.

CO₂ conversion is a central strategy for closing the carbon cycle and enabling sustain- able energy and chemical production through catalytic pathways. In this work, a descriptor-based, data-driven computational framework is employed to screen nanocatalysts for CO₂ conversion using density functional theory data reported in the literature. Key adsorption and electronic descriptors, including CO₂∗ and CO∗ binding energies, are analyzed to establish structure-activity relationships governing catalytic performance. Correlation and volcano-type analyses reveal that moderate adsorption strengths are essential for balancing CO₂ activation and product desorption, while excessively strong binding leads to surface poisoning and reduced activity. The results demonstrate that descriptor-guided screening can effectively rank catalyst candidates and provide rational design rules, without relying on new computationally intensive simulations. This framework offers a computationally efficient pathway for accelerating nanocatalyst discovery for CO₂ conversion.

To address the challenge of achieving both steady-state accuracy and fast dynamic response in permanent magnet synchronous motor (PMSM) systems equipped with LCL filters, this paper proposes a complex vector PI controller optimization method. The proposed approach extends the conventional real-axis PI control to the complex domain, enabling unified modeling of current decoupling and harmonic suppression. Based on this formulation, the response surface methodology (RSM) is employed to optimize the controller parameters. A quadratic response model is established through design of experiments (DOE), with steady-state error, dynamic overshoot, and harmonic suppression indices defined as optimization objectives to obtain the optimal parameter set. The core contribution of this work is the integration of a frequency-domain complex-vector model with a systematic multi-objective optimization framework using Response Surface Methodology (RSM) and Generalized Reduced Gradient (GRG) algorithms. This approach addresses the inherent coupling and resonance issues in LCL-filtered PMSM systems. Quantitative experimental results demonstrate that, compared with conventional tuning methods, the proposed strategy reduces the current settling time by 47.6% and suppresses torque overshoot by 92.8%, thereby achieving a superior balance between fast transient response and steady-state accuracy.

In this paper, an elliptical monopole antenna is modified and loaded with stubs and slots to improve filtering characteristics over tri-band operation. As the surface current is concentrated at the periphery of the monopole and decreases away from the feed, therefore, a slotted elliptical monopole is designed and sliced from the top. A rectangular strip is added at the top and center to create two symmetrical loops. A slot in each loop at a different position causes the antenna to operate over dual/tri-bands. A rectangular stub is added in the feed-line to improve the band-stop/filtering characteristics. The parameters of the structure are optimized to obtain S₁₁ ≤ -10 dB over 3.22-3.64 GHz, 5.53-6.03 GHz and 6.71-7.14 GHz for 5G, V2X, WLAN and Wi-Fi 6E applications. The three bands can be tuned independently. The compact 0.171λ₀ × 0.184λ₀ antenna, fabricated on 1.6 mm FR4 substrate (λ₀ is the free-space wavelength at 3.22 GHz), offers maximum S₁₁ of -0.9 dB and -4.9 dB, respectively, between the lower and middle bands and middle and upper bands. Minimum S₁₁ of -55 dB, -25 dB and -27 dB are obtained over the lower, middle, and upper bands respectively. The measured results validate the simulation ones.

This paper presents the ultraminiaturized implantable antenna based on a meander-line structure, specifically tailored for leadless pacemaker applications operating within the Wireless Medical Telemetry Services (WMTS) band of 1395-1400 MHz. The projected antenna has an ultraminiaturized volume of 3.25 mm³, surface area of 5 mm × 5 mm, and thickness of 0.13 mm. The substrate and superstrate were made of Rogers RO 3010 (ε_r = 10.2, tan⁡δ = 0.0035). Using a meandered line as the radiating element and including a shorting pin helps achieve impedance matching, reduces the overall antenna size, and improves the bandwidth performance. The proposed implantable antenna is validated using both homogeneous and heterogeneous heart phantoms. Experimental measurements were performed by embedding the antenna in minced pork tissue.; achieving a peak gain of -21.3 dBi and an impedance bandwidth of 360 MHz. Additionally, to ensure patient safety, Specific Absorption Rate (SAR) assessments were performed and the values are 202.52 W/kg (1-g) and 43.4 W/kg (10-g). With a 10 dB margin at 1.4 GHz, the results show that the antenna can successfully enable wireless communication at distances greater than 10 m.

This paper proposes a slot-loading-enabled compact ultra-wideband (UWB) planar antenna supported by circuit-backed modelling that targets defense communication systems. The antenna was realized on a compact footprint of 10 × 12 × 1.5 mm³, corresponding to an electrical size of approximately 0.29λ × 0.35λ × 0.043λ at the center frequency. Through the combined use of a modified circular radiator, strategically introduced slots, a stepped feed network, and a defected ground plane, the antenna achieves a continuous impedance bandwidth from 2.4 to 15 GHz. This corresponds to an absolute bandwidth of 12.6 GHz, a fractional bandwidth of nearly 145%, and a center frequency of 8.7 GHz, confirming the UWB operation. The antenna attains a maximum gain of 6.37 dB with a radiation efficiency reaching 89%. Stable radiation characteristics were observed, with dominant co-polarized fields and well-suppressed cross-polarization in both the principal planes. An electrical equivalent circuit provides physical insight into the multi-resonant behavior and enables efficient circuit-level validation. The measured results were in close agreement with the simulations, demonstrating the suitability of the antenna for compact UWB defense communication applications.

This paper focuses on enhancing the efficiency of wireless power transfer (WPT) using metamaterials (MTMs) only in the transmitter section, without modifying the receiver section. Power transfer efficiency (PTE) is the ratio of the actual power to the load resistance R_load that is transmitted to the load to the maximum available power at the source, V_s. Enhancing the PTE of a WPT system is essential, given the wide range of WPT applications. Magnetic MTMs can significantly increase the PTE. This research proposes a structure for the transmitter coil (Tx) and the receiver coil (Rx), incorporating the MTM slab, in a WPT system to enhance efficiency. The MTM was fabricated on a thin FR-4 substrate and positioned in front of and behind the Tx coil. Full-wave simulations show a clear improvement in coupling after adding the MTM plate. The transmission coefficient S₂₁ is increased by 0.4 when the MTM is placed in front of the Tx coil. When the two plates of the MTM were inserted, the S₂₁ improved by 0.2 compared to a single slab due to dielectric losses. In all cases, the magnetic field became more distributed and focused on the receiver side after the addition of the MTMs. The power transfer efficiency reaches 53.3% with double-layer MTMs at 12 MHz and a distance of 35 mm. Finally, the results of the measurements and simulations showed acceptable agreement, indicating that the proposed method is effective in overcoming reduced efficiency issues. The proposed design is suitable for various electronic applications, such as multiple-device charging pads.