A flexible ultra-wideband antenna is presented using a denim (jeans) textile substrate for wearable 5G and Internet of Things (IoT) applications. The antenna employs a coplanar waveguide (CPW) feed with a rectangular defected ground structure (DGS) etched in the ground plane to improve impedance matching. Bandwidth enhancement is achieved by introducing a nested U-slot in the radiating patch. The proposed design operates over the 1.28-6 GHz frequency range, providing an impedance bandwidth of approximately 4.72 GHz. The measured realized gain varies from 2.1 to 5.3 dBi, while the simulated radiation efficiency remains above 80% across most of the operating band. Good agreement between simulated and measured results confirms stable radiation characteristics, demonstrating the suitability of the antenna for wearable ultra-wideband and sub-6 GHz communication systems.

In this paper, a multiband patch antenna with harmonic suppression capability is developed for LoRa and GPS applications. The antenna configuration consists of a triangular patch as the primary radiator and a microstrip feed line as the excitation source. A parasitic element and a U-shaped slot are incorporated to generate the second and third resonance bands, while two stubs suppress the unwanted harmonics and improve impedance matching. The antenna is implemented on an FR-4 substrate (ε_r = 4.4), consisting of a main radiator measuring 84.5 mm × 92.45 mm, a parasitic element of 56 mm × 6.2 mm, a U-slot of 35 mm × 1.8 mm, and two stubs measuring 7 mm × 3 mm and 15 mm × 3 mm, respectively. The dimension of the antenna width and length are both 140 mm with a 50-Ω feed line of width 3 mm and length 19.5 mm. The bottom of the antenna contains a full ground plane. An extensive parametric study is conducted to optimize the antenna. The simulation and measurement results confirm that the antenna meets the -10 dB return-loss criterion throughout its operating frequencies with a bandwidth of 19 MHz (426-445 MHz) for the 433-MHz band, 13 MHz (916-929 MHz) for the 923-MHz band, and 19 MHz (1.559-1.578 GHz) for the 1.57-GHz band. The unwanted harmonics at 1.68 GHz, 2.00 GHz, and 2.67 GHz are successfully attenuated. The simulated current distributions, radiation patterns, and gain values for each band validate the antenna's multiband operation and harmonic-suppression capability.

This article presents a 12-element multiple-input multiple-output (MIMO) antenna system for fifth-generation mobile phones. To improve isolation, split-ring resonators are positioned adjacent to the radiating elements in the proposed design, which features a flower-shaped antenna radiator etched along the side frames of the device. The antenna system provides an isolation of over 15 dB between the elements with a wide operational band of 3.0-7.5 GHz. Simulations and experiments demonstrate that sublime presentations have an overall efficiency of 58%-78% across the operational band and an ECC of less than 0.05. Additionally, the impact of user's hand grip, plastic frame, and battery integration is analyzed. The robustness of the proposed design was confirmed by the alignment between the simulated and measured results.

The coupling of extensive metallic components within utility tunnels significantly complicates the earth-entry and dispersion pathways of cable short-circuit fault currents.This study focuses on a conventional three-compartment utility tunnel to guarantee steady and dependable operation of transmission lines. An integrated grounding system model with a concrete shell, vertical grounding electrodes, and grounding busbar bonding was constructed under various soil-resistivity conditions. The effects of bonding distance, vertical grounding electrode arrangement, and resistivity of the concrete shell on the grounding resistance, ground potential rise, touch voltage, and step voltage were methodically investigated by parametric simulations using CDEGS software. The findings indicate that an appropriate grounding grid spacing can significantly improve the electrical properties of the grounding system, whereas excessive density diminishes these advantages owing to the reciprocal coupling. The incorporation and deepening of the vertical grounding electrodes significantly diminished the ground resistance and ground potential rise. As the resistivity of the concrete shell increased, both the equivalent electrical parameters and surface potential gradient increased markedly. Research has shown that the interaction between the grounding network in utility tunnels and the adjacent soil influences fault-current dispersion pathways. This study provides a reference for optimizing the design of grounding systems for utility tunnels.

A circularly polarized (CP) millimeter-wave phased array antenna (PAA) is proposed for wide-angle scanning applications. The antenna is composed of radiating patches, coupling patches, and a ground plane. A single element consists of a centrally fed microstrip CP antenna with double arc-shaped slots, with a parasitic patch loaded on its top. A sequentially fed 2 × 2 subarray is constructed by arranging single elements in a specific orientation, and the central disc-ring structure is combined with the square ring patch structure based on the beam complementarity principle to broaden the beamwidth. Both simulations and measurements are performed on a 4 × 4 prototype array. The proposed antenna operates over a frequency band of 27.6-30.4 GHz, 3 dB AR bandwidth covers working bandwidth. When the beam scans to ±60°, the gain degradation relative to the boresight direction is only 1.1 dB, with the AR at the beam pointing angle maintained ≤3.5 dB. The proposed antenna boasts a compact size, facile fabrication process, and excellent wide-angle scanning capability, and it provides a novel design paradigm and practical solution for CP millimeter-wave wide-angle scanning PAA systems.

A multi-step deadbeat predictive control method for permanent magnet synchronous motors based on fuzzy adaptive particle swarm optimization (PSO) parameter identification is proposed to address the problem of performance degradation under parameter mismatch conditions. First, this method dynamically adjusts the learning factors of the PSO algorithm through fuzzy control, improving the convergence speed and stability of parameter identification. Secondly, this method can accurately identify key parameters such as stator resistance, inductance, and permanent magnet flux without the need for additional injection of excitation signals injections, effectively solving the problem of the under rank model under rank in traditional identification methods. The experimental results demonstrate that this method significantly improves the dynamic response speed and steady-state control accuracy of the system under parameter mismatch conditions, effectively suppresses speed fluctuations and current surges, improves current ripple characteristics, and provides a high-performance solution for high-precision driving scenarios such as CNC machine tools.

A dual adaptive neural network-based harmonic compensation algorithm is proposed to improve the low-speed machining accuracy of permanent magnet synchronous motor (PMSM) drives. First, the mechanism of harmonic current generation and its influence on torque ripple and speed fluctuation in PMSMs is analyzed. Second, the structure of the dual adaptive neural network is designed: the first network is used to extract harmonic current components in real time, and the second network dynamically generates corresponding harmonic voltage compensation signals to suppress current distortion, with the advantages of fast dynamic response and high compensation accuracy. Finally, the proposed method is verified on an experimental platform. The experimental results show that the 6th harmonic amplitude is suppressed from 0.094 to 0.016, and the 12th harmonic amplitude is reduced from 0.025 to 0.004, which is significantly better than the traditional compensation method. The proposed algorithm effectively reduces torque ripple and speed fluctuations, thereby improving the control accuracy and machining performance of the PMSM drive system.

This study proposes an improved output matching design technique based on a two-stage harmonic suppression network, with the core innovation being a hybrid matching mode combining microstrip lines and lumped-parameter components in the output matching. In the first-stage harmonic suppression network, a third-order Butterworth filter serves as the prototype. Utilizing the Richards transformation and Kuroda rule, it is converted into a cross-shaped microstrip line, achieving high-frequency matching while suppressing second-harmonic components. The second-stage harmonic suppression network employs two series-connected LC resonant circuits to suppress third- and fifth-harmonics, respectively. To broaden bandwidth and enhance circuit stability, an improved negative feedback structure based on a second-order Butterworth low-pass filter prototype is introduced. Practical circuit testing within the 0.4-1.2 GHz operating bandwidth demonstrated output power ranging from 40.1 to 41.3 dBm and drain efficiency exceeding 51.63%, robustly validating the effectiveness of this approach.

This article presents an enhanced-gain ultra-wideband (UWB) antenna with multiple notch responses to suppress the effects of coexisting wireless systems. The proposed antenna is developed in two stages. In the first stage, a reduced-ground U-shaped monopole with parasitic patches was designed to obtain a wide bandwidth between 3.02 and 10.76 GHz while maintaining a peak realized gain higher than 7 dB. In the second stage, selective frequency-rejection capabilities are tuned using split-ring structures (SRSs) for dual and higher-order notch responses. Two configurations are studied: dual-set SRS, which gives rise to low and high region notches centered at 5.73 GHz and 8.31 GHz, respectively, and higher-order SRS notch configuration providing a broad notch about 6.78 GHz with a 5.45% fractional rejection bandwidth. Parametric analysis indicated that the notch depth, notch bandwidth, and center frequency were independent and could be controlled via geometric tuning. The simulated results, supported by measurements from Keysight's PNA-X, corroborate the reflection coefficient, gain behavior, and notch performance; any deviations are attributed to variations experienced during the fabrication. The proposed approach achieves a UWB, increased gain, and flexible interference suppression, qualifying it for modern UWB communication systems that require a compact design.

A novel integration method of a polarization conversion metasurface (PCM) and an array antenna for radar cross-section (RCS) reduction is presented. This method combines the PCM with a slot array antenna operating at 11.5 GHz for reducing RCS. The metasurface is composed of polarization conversion units arranged in a checkerboard pattern, and each PCM unit cell is made up of two symmetrical fork-shaped structures. The polarization conversion units can achieve a polarization conversion rate of over 90% in the frequency band of 10.12-19.93 GHz (65%). The measurements demonstrate that the antenna attains over 10 dB RCS reduction in the frequency range of 9.9-20.7 GHz (71%). Meanwhile, the radiation performance of the antenna is effectively preserved.

Microwave heating, widely employed in the food industry, offers significant advantages due to its volumetric heating capabilities. However, its efficiency is often hindered by non-uniform heating patterns. This study aims to analyse heating patterns in a rectangular, single-fed domestic microwave oven, leveraging cost-effective methodologies. Theoretical analyses, electromagnetic simulations, and experimental measurements were conducted to characterise the resonant modes within an empty cavity and with a load. The mathematical computation of multiple mode superposition within the cavity was performed for two domestic microwave ovens. Mathematical and experimental analyses demonstrate a close agreement in results. The findings reveal that mode distribution, influenced by cavity dimensions, load properties, load placement, and magnetron characteristics, significantly impacts heating patterns. This study helps us understand that in spite of the dynamic nature of magnetron, it is important to superimpose multiple resonant modes prevalent within the cavity to understand influences on microwave heating pattern of any food materials.

With the rapid development of technologies such as Big Data, Cloud Computing, Artificial Intelligence (AI), and Internet of Things (IoT), there is an increasing demand for real-time computing and low-latency data transmission. Mobile Edge Computing (MEC) technology has been proposed to reduce data transmission latency and alleviate the burden on the core network, but MEC still faces the problem of limited computational resources and bandwidth in high-density device environments. To address these issues, this study proposes a joint optimisation energy-efficiency maximisation strategy for Intelligent Reflective Surface (IRS)-based Unmanned Aerial Vehicle (UAV) and Device-to-Device (D2D) collaborative Mobile Edge Computing (MEC) systems. The strategy integrates optimisation of task offloading decisions, UAV trajectory planning, computational resource allocation and IRS phase regulation to maximise the energy efficiency of the system. The highly coupled and non-convex optimisation problem is solved iteratively by designing a twoloop iterative optimisation framework combining Dinkelbach's algorithm with the block coordinate descent (BCD) method using the Lagrange multiplier method and the successive convex approximation (SCA) technique. Simulation results show that the optimisation strategy in this study significantly improves the energy efficiency of the system compared to the conventional scheme, especially in IRS phase optimisation and UAV trajectory adjustment.

This study proposes a novel π-type circuit topology designed to achieve broadband and flat negative group delay (NGD) characteristics. Featuring a simple structure composed entirely of passive lumped elements, the proposed design offers significant advantages in terms of ease of fabrication, low cost, and seamless integration into larger microwave systems. First, a comprehensive theoretical analysis was conducted to establish the operational principles and derive the design equations. We then systematically investigated the sensitivity of the circuit's performance to variations in individual component values, which provides crucial guidelines for practical implementation. To validate our theoretical findings, a physical prototype with compact dimensions of 32 mm × 35 mm was designed and fabricated. Experimental results demonstrate that at the center frequency of 107.5 MHz, the circuit achieves an NGD of -2.27 ns with an insertion loss of 19.5 dB. Notably, the circuit maintains a wide flat NGD bandwidth of 151 MHz, exhibiting a group delay fluctuation of merely 4.1% across the band. These results confirm the effectiveness and robustness of the proposed circuit for broadband microwave applications.

Sparse arrays have been extensively investigated for their capability to enhance degrees of freedom (DOFs). However, conventional nested array configuration is susceptible to strong mutual coupling (MC), while its achievable uniform DOFs (uDOFs) remains limited. To address these challenges, this paper proposes two optimized hierarchical nested arrays, designated as OHNA-I and OHNA-II. OHNA-I reconstructs the spatial arrangement of subarrays through a hierarchical shifting operation, effectively extending the continuous segment of the difference co-array (DCA). Building on this, OHNA-II further optimizes the subarray geometry via sensor displacement, achieving a better balance between uDOF enhancement and MC suppression, thereby maintaining higher uDOFs while reducing inter-sensor coupling interference. Numerical simulation results demonstrate that, under the same number of physical sensors, the proposed structures - particularly OHNA-II - achieve a greater number of uDOFs than existing classical sparse arrays. Furthermore, in scenarios with strong MC, the proposed structure exhibits superior robustness and lower root mean square error (RMSE) in DOA estimation.

This paper presents a fast and efficient modeling approach based on the volume integral method for the characterization of AC losses in high-temperature superconducting coils made of second-generation Rare-earth Barium Copper Oxide (ReBCO) tapes. Three modeling strategies are investigated and compared, considering the detailed multilayer tape configuration, the homogenized tape configuration, and the simplified single-layer superconducting tape representation. These approaches aim to evaluate the impact of geometrical and electromagnetic simplifications on the accuracy of the results while significantly reducing computational time. In particular, the homogenization of the electromagnetic properties of the tape is explored to accelerate simulations without compromising the accuracy of key physical quantities such as AC losses and current density distribution. The modeling results are compared to measurements.

This study proposes a broadband, wide-angle metasurface for bistatic radar cross-section (RCS) reduction by integrating a low-profile bent-line unit design with an Adaptive Binary Particle Swarm Optimization algorithm enhanced by Array Pattern Synthesis (ABPSO-APS). The optimized metasurface achieves over 10 dB of bistatic RCS reduction across 8.4-21 GHz (86.7% fractional bandwidth), with a peak reduction of 22 dB, outperforming conventional checkerboard, genetic algorithm, and particle swarm optimization layouts by 22.82%, 15.27%, and 7.91%, respectively. The design also exhibits angular stability up to 30° and polarization insensitivity under both TE and TM incidences, while maintaining an ultrathin profile of only 0.1λ (where λ is the wavelength at the center frequency). These results demonstrate its strong potential as a compact and efficient solution for advanced electromagnetic stealth and radar signature control applications.

Supplying battery-free power to wireless sensor systems (WSS) mounted on rotating shafts remains a major challenge due to limited installation space, low rotational speed, and the requirement for long-term autonomous operation. This paper presents a compact dual-rotor energy harvester (EH) based on multilayer printed circuit board (PCB) sheets, designed for powering WSSs installed on ship propulsion shafts. Stacked multilayer PCB coils forming a three-dimensional structure are arranged on both the inner and outer rotors to enhance magnetic flux linkage and power density. The experimental results show that the EH generates power levels up to 959 mW at a shaft speed of 300 rpm. The output power improved nonlinearly with increasing rotational speed, demonstrating its suitability for real-time monitoring applications. The proposed EH offers a promising solution for powering WSS in autonomous driving technologies, with the potential for further optimization and integration into various mobility systems.

This work presents a dual-band circularly polarized antenna array in which adjacent elements are excited with quadrature phase progression using a cascaded hybrid-coupler feeding network comprising one rat-race coupler and two branch-line couplers. Double-T monopole elements enable dual-band operation, achieving impedance bandwidths of 300 MHz (2.4-2.7 GHz) and 975 MHz (5.025-6 GHz) with corresponding axial-ratio bandwidths of 110 MHz and 525 MHz. The array provides peak gains of 9.19 dB and 9.49 dB with simulated radiation efficiencies of 90% and 87% in the respective bands. The array yields peak realized gains of 9.19 dBic and 9.49 dBic with simulated total efficiencies of 90% and 87% in the corresponding bands. Unlike sequential rotation or multilayer CP arrays, the proposed single-layer planar hybrid-coupler network ensures frequency-stable dual band circular polarization. An analytical formulation of the array factor and axial ratio sensitivity is provided to clarify the CP synthesis mechanism and its suitability for compact vehicular platforms.

The phase noise levels of the output signals provided by two CRLH (Composite Right-/Left-Handed) distributed oscillator configurations are measured and compared. The first CRLH oscillator configuration provides two output signals, drain-line and gate-line output signals, available at the ends of the drain-line and gate-line that are not used for connecting the oscillator feedback. The second CRLH oscillator configuration is obtained by adding a Wilkinson power combiner to the first configuration that sums the drain-line and gate-line output signals for a single-output signal, a combined output signal. The experimental results show that the best performance in terms of output power and spectral purity can be obtained for the single-output CRLH oscillator.

In this letter, a frequency and linear polarization(LP) reconfigurable antenna is proposed. The antenna consists of two pairs of printed dipoles as the primary radiating patches. By independently controlling the direction of flowing current using loaded PIN diodes, the dynamic reconfiguration of both frequency and linear polarization (LP) can be realized. In addition, a dual-band artificial magnetic conductor (AMC) reflector is added under the radiator, which can effectively reduce the antenna profile to 0.1λ₀ (12.4 mm, where λ₀ is the wavelength at low operating frequency). Both simulated and experimental results show that the proposed antenna can operate in four modes: 0° LP low frequency (2.36-2.77 GHz) state, 0° LP high frequency (3.25-3.68 GHz) state, 90° LP low frequency state, and 90° LP high frequency state. The antenna exhibits stable radiation patterns, with gain values of 7.56 dBi in the low frequency state and 8.03 dBi in the high frequency state. This antenna is suitable for ISM band applications, such as Wi-Fi (2.4-2.48 GHz) and Bluetooth (2.4-2.48 GHz), as well as TDD Band 42, meeting the requirements of modern wireless communication systems.