In this paper, an ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna covering the n77, n78, n79, and 6 GHz bands is proposed for 5G applications, which achieves the full coverage of the 5G NR (New Radio) band with a compact geometry. The antenna is fabricated from low-cost printed circuit boards, with the dimensions of 36 mm x 53 mm x 1.6 mm. The MIMO antenna has been designed with two positive octagonal antenna monopole elements, which feature triangular fractal slots and a defected ground plane. Each of these elements is excited by a microstrip feed, and the antenna operates within a bandwidth of 2.92-16.97 GHz, which encompasses the entire UWB frequency range. The utilization of a floor with T-shaped slots and T-shaped stubs serves to minimize the generation of coupling currents between the antenna elements, thereby achieving an isolation of in excess of 19 dB across the entire operating band and a figure in excess of 20 dB in multiple 5G bands. In addition, simulations and measurements show that the antenna has an envelope correlation coefficient (ECC) less than 0.005, a diversity gain (DG) more than 9.98, a total active reflection coefficient (TARC) less than -30 dB, and a channel capacity loss (CCL) less than 0.3 bit/s/Hz in the operating frequency band, with good gain and stable radiation characteristics. The designed antenna has the potential for significant applications in 5G wireless communications.

Current research on passive millimeter wave (PMMW) human security imaging mainly focuses on system optimization and image processing algorithms, with limited attention on simulation studies. This paper addresses this gap by developing a PMMW imaging simulation for human security screening. The study proposes a Multi-layer Brightness Temperature Tracing Method (MBTTM) to accurately calculate brightness temperature values across various scattering directions. The paper proposes a simulation model for microrough surfaces based on the rough characteristics of human skin in security check scenarios. It also presents a PMMW brightness simulation model for detecting hidden dangerous goods in hierarchical media. The model incorporates diffuse ray tracking and accounts for transmission phenomena when rays interact with penetrable surfaces. Finally, both simulation and experimental validation are conducted for human security scenes.Experimental results demonstrate the effectiveness of the proposed method in detecting concealed objects, with a detailed analysis of the impact of surface roughness, ray spacing, and concealment depth on imaging quality.

Taguchi method has been extensively applied in electromagnetic optimization. To further enhance the optimization efficiency of the Taguchi method, a surrogate-assisted Taguchi method employing dynamic reduced rates is proposed. The reduced rate of each design variable is proportional to its contribution percentage. Variables with higher contributions exhibit a larger reduction rate, which subsequently decreases the search step and enhances the exploitation and convergence of the Taguchi method. The Kriging model serves as a substitute for the real fitness evaluation in predicting the result of each experiment, with its feasible state determined by the average relative error of its predictions. This ensures the prediction accuracy while reducing the number of real fitness evaluations. The proposed algorithm is validated by the fact that the efficiency has increased at least twofold through four benchmark function tests. In the end, this algorithm is employed to synthesize the radiation pattern of an asymmetrical dipole array with 16 elements and to optimize the front-to-back ratio of the Yagi-Uda antenna.

In this paper, an integrated rectifying metasurface harvester with small dimensions, wide-angle incidence, and polarization insensitive characteristics is proposed. The proposed structure is assembled from a periodic unit cell, diodes, and loads, which makes the structure simple and less expensive to manufacture. The centrosymmetric design concept of the unit cell structure enables the proposed metasurface harvester to capture incident waves with arbitrary polarization angles and over a wide incident angle range of 60°. A 5 x 5 metasurface array was fabricated for real measurements. The results show that the measured efficiency is 62.07% near the operating band 5.8 GHz when the incident power is 15 dBm. When the polarization angle of the incident wave is changed, the efficiency remains essentially constant. As the angle of incidence changes, the efficiency shows a certain decrease, but it can still maintain an efficiency close to 50% near the operating frequency band. The proposed harvester can supply energy to low power devices as well as sensor nodes in IoT.

This article presents experimental measurements and theoretical calculations of the mass normalized extinction cross section (extinction efficiency) of hydrothermally synthesized copper nanofibers in the infrared spectral region (2-14) µm. The synthesized copper nanofibers have an average diameter of 40 nm, and the length of the fibers has been ultrasonically reduced to achieve the highest possible efficiency in the targeted IR spectral region. A peak extinction efficiency of ~30 M²/g is achieved with an overall efficiency greater than 10 M²/g across the remainder of the infrared window. Such high efficiency fibers make them of high interest for applications that require attenuation of electromagnetic radiation. To the best of our knowledge, this efficiency is the highest that has been reported in literature, and the synthesis procedure is simple and can be scaled-up for mass production of copper nanofibers.

In this paper, a six-order cross-coupled ceramic dielectric waveguide filter (CDWF) based on equilateral triangle resonators is introduced. It is composed of a regular hexagonal cavity, which is divided into six equilateral triangular blocks. The filter exhibits two transmission zeros outside the passband that ensure its out-of-band suppression greater than 45 dB. Measured results show that the insertion loss is less than 1 dB and the return loss more than 16 dB within the operating frequency range of 3.4-3.6 GHz. The ceramic dielectric used here has a dielectric constant of 20.3 and a thickness of 5 mm. Thus, it has the advantages of compact size and excellent frequency selectivity.

Generally, the array pattern synthesizing can be shaped by controlling the excitation amplitude and phase of the individual elements of the antenna array which they could be controlled either separately or jointly to provide most flexible solutions for the desired pattern shaping. In this paper, a new controllable trapezoid phase-only taper is proposed. In practical applications, phase-only tapers are more preferable than amplitude-only tapers due to their desirable advantages. The required pattern shaping with fulfilled user-defined constraints on the sidelobe peaks, beam widths, and steered nulls can be achieved by optimizing only the excitation phases of the trapezoidal taper. More importantly, the proposed trapezoidal taper offers the best tradeoff between the array directivity and undesirable sidelobe pattern. In addition, the element excitation amplitudes of the proposed phase-only trapezoid taper are made constant and equal to that of the original trapezoid taper function. Thus, it enjoys low array complexity. Moreover, the manipulated phases are assumed to be symmetric to further simplify the array feeding network. The genetic algorithm was used to optimize only the half number of the elements' phases. The results show that the phase-only trapezoid taper yields identical main beam shape to that of the amplitude-only trapezoid taper and much better than the other conventional tapers. Furthermore, it is found that the trapezoid phase-only method needs more variable elements than the trapezoid amplitude-only method to achieve almost the same performance. Thus, the complexity reduction percentage of the phase-only method is lower than that of the amplitude-only method.

In the present work, a dual-band four-port multiple-input multiple-output (MIMO) antenna based on an FR4 substrate is designed, which can work in the frequency bands of 5G n256/n77/n78/n79 and 6G system. The MIMO antenna is composed of four orthogonally placed monopole antennas. Multiple sets of L-shaped branches and cross-shaped branches are added to improve the isolation among the antenna elements. The measured isolation is below -20 dB, and most of them can reach -30 dB within the operational frequency spectrum. The actual measurement results reveal that the two impedance bandwidths of the antenna are 420 MHz (1.95-2.37 GHz) and 4050 MHz (3.2-7.25 GHz), respectively, which can encompass the n256 band for 5G-6G satellite technologies (1.98-2.01 and 2.17-2.2 GHz), 5G n77/n78/n79 (3.3-4.2/3.3-3.8/4.4-5.0 GHz) and 6G band (6.425-7.125 GHz). At the same time, the antenna features a peak gain of 7.4 dB. The ECC value is below 0.0015, while the DG value exceeds 9.9999, showing good diversity performance. The data reveal that the designed dual-band quaternary MIMO antenna has good applications in the fields of 5G satellite communication and 6G systems.

High-precision Direction of Arrival (DOA) estimation requires the use of a large-scale antenna array to achieve accurate results. However, the increasing number of antennas brings substantial challenges that hinder the practical implementation of DOA estimation in real-world engineering applications. The complexity and cost associated with deploying extensive antenna systems can be prohibitive. In contrast, digital metasurfaces offer a promising solution by dynamically manipulating electromagnetic waves. These advanced surfaces enable precise control over wavefronts while utilizing significantly fewer elements, leading to a more compact and cost-effective approach without sacrificing the high-resolution capabilities necessary for effective DOA estimation. This innovative technology not only simplifies the design but also enhances performance. To provide insights for future advancements in this field, this paper reviews the current research status of various DOA estimation techniques that integrate metasurfaces with conventional wave-direction estimation systems, highlighting their potential and applications in improving DOA estimation accuracy.

An ultra-compact isolator based on the integration of aluminum-substituted cobalt ferrite films with magneto-optical activity to a silicon microring resonator is suggested. The strong remanent magnetization of the employed magneto-optical material allows the operation of the device without any external magnetizing elements, and the device footprint is only 150 μm². A prototype chip has been fabricated using conventional processes compatible with the silicon on an insulator platform, and a maximum isolation ratio of 7 dB at the 1557.6 nm wavelength has been achieved. To the best of our knowledge, this is the most compact photonic isolator demonstrated to date, and it is suitable for all-optical circuits with extremely high integration density.

The proposed antenna system integrates advanced materials electromagnetic properties tuning to allow real-time steering to the antenna main beam direction. We explore a tuning mechanism based on changing the chemical potential differences (μc), through including a chiral single wall carbon nanotube (SWCNT) structure with a plasmonic resonance effect at the optical regime. Such change in the value of μc realizes a manipulation in the angular emission pattern change to enhance the beamforming capabilities to the desired requirements. This steerability provides substantial benefits for applications such as optical communication systems. The obtained results validate that the proposed nano-dipole antenna shows significant improvements over other traditional antennas in terms of size reduction with acceptable radiation efficiency, directivity, and tunability. The integration of the proposed design within next optoelectronic generations can floor the way to the compact, high-performance systems with enhanced capabilities for optical communication systems and photonic circuitry. This study presents a steerable plasmonic nano-dipole antenna with dynamic electromagnetic radiation control, designed for modern communication. The antenna operates across a wide frequency range, with a primary focus on the visible spectra 300 THz to 700 THz. By utilizing resonant plasmonic effects, the antenna achieves a radiation efficiency of 57% and a directivity of 4.5 dBi. We introduce a beam-steering mechanism that enables angular radiation steering up to ±25° from the central axis. Control mechanisms include electrical tuning via applied μc voltage from 0 V up to 1 V and optical tuning using laser excitation around 600 THz. Simulations confirm that beamwidth narrows from 30° to 10° at resonance, enhancing spatial precision. The validated results show a tunability of 200 THz in the operational wavelength, with a response S11 below -10 dB. These features demonstrate that the antenna operation has a potential for integration into next-generation optoelectronic devices, offering compact and efficient solutions for wireless communication, remote sensing, and optical imaging systems. This is achieved by leveraging the resonant interaction between surface plasmon polaritons and nano-dipole geometry, and we demonstrate the ability to achieve highly directional and tunable radiation across a wide range of frequencies, including visible and near-infrared spectra.

An exact analytical solution is obtained for the problem of finding the field of a linear electric current located near the interface between half-spaces filled with ordinary and perfectly matched double-negative media. To achieve this, a novel approach is introduced that, for the first time, enabled the correct analytic continuation of the function describing the field into the entire half-space filled with a double-negative medium. The analysis of this solution shows that the current source field, upon reaching the point of perfect focusing, passes through it and then moves off to infinity, rather than disappearing at that point, as claimed in earlier works.

To satisfy the demand for 5G communication to smartphone terminal antennas in element quantity and isolation, an eight-element broadband MIMO antenna system with high isolation is proposed in this paper. The antenna element consists of an L-shaped feed line and a rectangular slot with an open slot. Meanwhile, a stepped impedance tuning structure was integrated within the rectangular slot to optimize broadband impedance matching and expand the operational bandwidth. In addition, a Chinese character ``工''-shaped defective ground structure has been innovatively designed to reduce surface wave coupling on the ground plane, achieving an isolation level of over -15 dB. Furthermore, eight antenna elements and six defective ground structures are symmetrically distributed along the long edges of the substrate, with coupling feeding performed through the L-shaped feed lines. The proposed antenna system ultimately achieves an operating bandwidth of 3.4-6.5 GHz below -10 dB, with a total efficiency greater than 90% and an envelope correlation coefficient of less than 0.016. The stability of the system in overlay screen mode, as well as in single-handed and dual-handed smartphone operation modes, is also demonstrated to showcase its practical applications.

Since the traditional Delta-shaped motor is difficult to achieve the wide speed range while increasing the output torque, it cannot fully meet the complex working conditions of electric vehicles. This paper, from the driving conditions and the principle of variable leakage magnetism, based on the traditional Delta-shaped interior motor, designs a variable leakage flux permanent magnet synchronous motor with a segmented Delta-shaped rotor permanent magnet structure (VLF-DSPM). The permanent magnet is segmented into a magnetic bridge by a ferromagnetic material so that some magnetic lines do not pass through the permanent magnet but directly through the magnetic bridge to increase the d-axis inductance. A magnetic barrier is designed in the q-axis to achieve magnetic leakage in the high-speed region, thereby achieving a wide speed control range. In addition, since the utilization rate of the permanent magnet is reduced due to segmentation, the output torque is reduced. Therefore, transverse bar-shaped permanent magnets are added to increase the reluctance torque of the motor to achieve a higher resultant torque. The key parameters of this structure were then optimized, and finally the electromagnetic characteristics of the VLF-DSPM were studied using finite element analysis in comparison with a conventional Delta-shape interior permanent magnet (DS-IPM) synchronous motor. The results show that the VLF-DSPM has better flux control capabilities, higher output torque, a wider speed range, and higher efficiency and power factor.

To achieve high-precision synchronous control of multiple motors, this study utilizes a permanent magnet synchronous motor as a case study. It adopts a fuzzy internal model proportional-integral-derivative algorithm with integral separation for single-motor control. On this basis, the virtual spindle synchronization strategy of multi-motor synchronous control and the fuzzy control algorithm are further introduced to adjust the feedback torque compensation coefficient dynamically, optimizing the virtual spindle synchronization strategy. The results showed that in single-motor control, the dual closed-loop fuzzy proportional-integral control algorithm achieved a torque fluctuation error of 4 N.m when the load torque changed significantly. The fuzzy internal model proportional-integral-derivative control algorithm with integral separation had a relatively smooth adjustment process, and the maximum torque fluctuation did not exceed 1 N.m. In multi-motor synchronous control, the improved virtual spindle synchronous control strategy had a synchronization error of only 14.2 r/min between motor 1 and motor 2, as well as between motor 1 and motor 3. The single-motor and multi-motor synchronous control strategies used in the study have high control accuracy and response efficiency, which is conducive to improving the synchronization accuracy and coordination between motors. The improved strategy provides a reliable control scheme for industrial automation systems.

Synthetic aperture radar (SAR) ship detection plays a significant role in ocean monitoring. However, the current SAR ship detection methods face limitations in detecting small and dense ships. To address these issues, a novel SAR ship detection method based on multi-scale feature cross-fusion (MFCNet) is proposed in this paper. In the proposed model, a feature extraction network with a spatial fusion attention mechanism (FESNet) is designed to improve the capability of the backbone network in feature extraction. A multi-intersection spatial pyramid pooling (MISPP) module is proposed to expand the receptive field and enhance the semantic information. Furthermore, a feature cross-fusion network (FCFNet) is designed to comprehensively integrate features of different scales for enhancing SAR ship detection performance. Experimental results demonstrate that the proposed model achieves high detection performance on the SSDD and HRSID datasets, providing more reliable technical support for ship detection in maritime environments.

A novel frequency and polarization reconfigurable water patch antenna is proposed for radio communication in the UHF band. Based on theoretical analysis and simulation results, water is an ideal material for designing transparent liquid ground. Water enhances outstanding transparency, excellent aesthetics, and high optical stealth performance for a wider range of application scenarios. The entire structure is made with polyvinyl chloride material and distilled water, except for the feed structure. By filling different cavities with liquid water, six different operating states are obtained in 1.924-2.5 GHz (26.1 %), 1.67-2.33 GHz (33 %), 0.644-2.288 GHz (112.1 %), 1.975-2.54 GHz (25 %), 1.748-2.108 GHz (18.7 %), and 1.988-2.348 GHz (16.6 %), achieving frequency reconfigurability. The antenna can be flexibly switched between linear polarization (LP) and two right-handed circular polarization (RHCP) states. The results show that the 3 dB axial ratio (AR) bandwidth covers 1.93-2.08 GHz (7.5 %) and 2.06-2.132 GHz (3.5 %). The antenna achieves high optical transparency of 100 % and a peak gain of 7.97 dBi.

This work addresses a wideband dual-beam 1x4 phased MIMO array antenna with a hybrid coupler for Industrial, Scientific and Medical (ISM) bands applications at 2.4-2.5 GHz. We engineered, refined, and reduced the fundamental component utilizing the novel concept of an advanced curved quarter-wave impedance adapter, achieving a 50% reduction in size relative to comparable designs documented in the literature. The fundamental component operates at 2.45 GHz, including a narrow bandwidth of 26 MHz and a maximum gain of 7.21 dB. Subsequently, a lossless magic-T power splitter is employed to feed two identical miniaturized elements resulting in a compact 1 × 2 array antenna with miniaturized size and enhanced performance. The results obtained show that the miniaturized 1 × 2 array antenna resonate at 2.45 GHz with a narrow impedance bandwidth of 52 MHz, peak gain of 9.41 dB and a peak directivity of 9.48 dB at 2.45 GHz. To broaden the narrow bandwidth and to enhance gain, directivity and radiation coverage area, a 3 dB hybrid coupler is used to feed two identical miniaturized 1 × 2 array antennas resulting a wideband directional dual-beam MIMO phased 1 × 4 array antenna. The proposed dual-beam array antenna prototype has been designed and fabricated on a substrate Rogers RT/duroid 5880 with the following parameters: relative permittivity ε_r = 2.2, dielectric loss tangent of 0.0009, and total size of 240 × 136 × 1.56 mm³. The simulation results are corroborated by experiments that verified the proposed dual-beam MIMO array antenna which exhibits a high gain of 11.2 dB, effective adaptation, an expanded bandwidth of 1.22 GHz, in addition to its MIMO capability and the dual beams oriented at ±30˚, achieved through switching between the two input feed ports of the hybrid coupler.

Periodic optical structures, such as diffraction gratings and numerous photonic crystals, are one of the staples of modern nanophotonics for the manipulation of electromagnetic radiation. The array of subwavelength dielectric rods is one of the simplest platforms, which, despite its simplicity exhibits extraordinary wave phenomena, such as diffraction anomalies and narrow reflective resonances. Despite the well-documented properties of infinite periodic systems, the behavior of these diffractive effects in systems incorporating a finite number of elements is studied to a far lesser extent. Here, we theoretically and numerically study the evolution of collective spectral features in finite arrays of dielectric rods. We develop an analytical model of light scattering by a finite array of circular rods based on the coupled dipoles approximation and analyze the spectral features of finite arrays within the developed model. Finally, we validate the results of the analytical model using full-wave numerical simulations.

We have developed a hyperspectral laparoscope capable of hyperspectral imaging during surgery. Using this hyperspectral laparoscope, we acquired hyperspectral images of fresh lymph nodes during colorectal cancer surgery. By integrating an improved U-Net algorithm specifically tailored for hyperspectral imaging, we achieved a recognition accuracy of 94%. Our results demonstrate that the multimodal hyperspectral imaging system has a great advantage and potential in label-free intraoperative diagnosis of lymph node metastasis in colorectal cancer.