This paper describes the design methodology of a compact multiband microstrip patch antenna intended for next-generation wireless communication applications. The proposed antenna operates over seven distinct frequency bands: 1.25-1.32 GHz, 2.30-2.44 GHz, 2.50-2.75 GHz, 2.92-3.25 GHz, 3.40-3.65 GHz, 3.70-4.23 GHz, and 4.70-6.0 GHz. These operating bands support a wide range of wireless services, including LTE, 5G communications, Wi-MAX, ISM applications, radar systems, and broadband wireless communications. Multiband performance is achieved through the incorporation of three strategically placed slits in the radiating patch along with a square split-ring resonator (SSRR). By adjusting the dimensions of the slits and the position of the SSRR, the operating frequency bands can be effectively tuned. The proposed antenna occupies a compact footprint of 40 × 40 mm² and consists of a radiating patch, a partial ground plane, and an SSRR structure. Simulation results demonstrate resonant frequencies at 1.3, 2.38, 2.66, 3.0, 3.5, 4.2, 4.9, and 5.7 GHz. Owing to its compact size, multiband capability, and simple structure, the proposed antenna offers advantages in terms of reduced cost, lower system complexity, and miniaturization, making it suitable for modern wireless communication systems.

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

To address the issues of narrow gain bandwidth and severe element coupling faced by traditional Fabry-Perot resonant antennas in phased array feed systems, this paper proposes a decoupling design method based on highly optimized resonant mode height. By analyzing electric field distributions and coupling mechanisms under multi-feed conditions, an improved resonator height calculation formula suitable for phased array feeds is derived, achieving mutual suppression of energy between reflected wave coupling and inter-element coupling. A 2 × 2 microstrip antenna array was employed as the feed source. Combined with a multilayer positive phase gradient partially reflective surface, a Fabry-Perot antenna prototype operating at 28 GHz was designed and fabricated. Simulated and experimental results demonstrate that compared to conventional designs, this antenna achieves a maximum gain at 28 GHz increased from 21.80 dBi to 23.15 dBi, with the 3-dB gain bandwidth expanded from 1350 MHz to 1730 MHz. This study provides an effective approach for achieving a broadband high-gain design in phased array-fed Fabry-Perot resonant antennas.

A wideband circularly polarized (CP) dielectric resonator antenna (DRA) with integrated harmonic suppression is proposed. The design transforms the original rectangular coupled slot into a branched configuration to perturb the electric field distribution within the dielectric resonator (DR) and ground plane, thereby obtaining wideband circular polarization characteristic. For harmonic suppression, a double-ended feeding structure integrated with a π-shaped stub and a transverse stub is introduced, generating four radiation nulls. Furthermore, a stepped-impedance feeding line is employed to extend the upper stopband bandwidth. A prototype is fabricated and measured; the experimental results and simulations are generally consistent. The antenna achieves a -10 dB impedance bandwidth of 40.2% (2.86-4.3 GHz), a 3 dB axial ratio bandwidth of 26.13% (3.06-3.98 GHz), an average gain of 5.3 dBi, and harmonic suppression of 2.7f₀ (where f₀ is the center frequency). The out-of-band suppression in both upper and lower stopbands exceeds 15 dB.

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.