A compact antipodal Vivaldi antenna (AVA) integrated with circularly shaped loads and some elliptic slits etched in tapered slots is proposed in this paper. First, the elliptic slits etched in two tapered slots are employed for wideband application in X-band. Then, the value of max power capacity increasing from 0.47 MW to 0.82 MW is mainly due to two circularly shaped loads. Moreover, the size of the antenna is decreased to 0.44λ_middle × 0.42λ_middle. The configuration is measured to confirm the simulated results. Based on these, a novel antipodal Vivaldi antenna with compact size is successfully designed and applied in high-power field at X-band.

This study aims to improve the efficiency of constructing basis functions for solving the electromagnetic scattering problem of objects using the method of moments combined with compressive sensing and Krylov subspace. To this end, a region decomposition method based on a clustering algorithm is proposed to accelerate the construction process of Krylov subspace basis functions. First, the midpoints of the common edges of triangular pairs are used to form a clustered dataset. Then, the initial clustering center is set, and the processes of clustering center updating and regional decomposition of the constructed dataset are completed iteratively. Finally, each subdomain is expanded according to the average distance from data points to the clustering center to ensure the continuity of currents. The numerical computation results show that the proposed method can achieve significant time efficiency.

In recent years, uncertainty analysis has become a hot topic in the field of Electromagnetic Compatibility (EMC), and non-intrusive uncertainty analysis methods have been widely applied due to their advantage of obtaining results without modifying the original solver. Among them, the Surrogate Model Method has attracted widespread attention from researchers in the field of EMC due to its high computational efficiency and resistance to the curse of dimensionality. However, the issue of determining the convergence of the surrogate models seriously affects the computational efficiency and convenience of this method in practical applications. To address this issue, a convergence determination method for uncertainty analysis surrogate models based on Mean Equivalent Area Method (MEAM) is proposed in this paper. The complete convergence time of the Surrogate Model Method can be accurately determined through iterative calculation by this method, and the effectiveness of the proposed method is verified by calculating parallel cable crosstalk prediction examples from published literature. Finally, based on the proposed convergence determination method, the real-time convergence determination problem of the Surrogate Model Method is also preliminarily discussed in this paper, and by establishing a polynomial relationship, the real-time convergence of the Surrogate Model Method can be roughly determined.

Conventional sidelobe reduction methods such as analytical or parametric approaches and complex numerical optimization approaches were accomplished via specific tapering windows. Among all of the tapering windows, a rectangular window gives simplest array feeding network, narrower beam width, and highest directivity. The only drawback is its highest sidelobe level due to sharp edges at the array ends. In this paper, a simple trapezoid taper window, which is something between typical rectangular and triangular windows, is first suggested as a best compromise between uniform and non-uniform amplitude window functions. Then, it is further developed by making it adaptive or adjustable by including a number of controllable-amplitude elements in the linear edges of the trapezoid window. Thus, the proposed taper window becomes very flexible to accommodate different user-defined constraints. To find the optimal values of those controllable-amplitude elements, a genetic optimization algorithm is used to design and optimize the trapezoid window such that a desired sidelobe peaks and controlled nulls can be met while maximizing the complexity reduction as much as possible. The linear and planar antenna arrays are simulated to validate the superiority of the proposed taper window.

This work focuses on the design and implementation of a dual-wideband asymmetric square-shaped slot radiator with coplanar waveguide (CPW) feed for circular polarization (CP) characteristics. The proposed radiator has inward ground plane extensions in the form of square and rectangular strips on the diagonal corners of the slot. By optimizing the size of strips, a dual-band antenna with CP behaviour is obtained. The inverted L-shaped grounded strip improves axial ratio bandwidth (ARBW). The extended signal line terminated in a wide tuning stub significantly improves impedance bandwidth (IBW) and ARBW. The designed asymmetric slot radiator is fabricated using an FR-4 substrate material of dimensions 50 × 50 × 1.6 mm³. This antenna design gives flexibility to alter polarization sense at the dual frequency bands. Further, edge effects are analyzed through electric field distribution, and their impact on impedance and AR characteristics are studied. It is designed, fabricated, and tested, and shows right-hand circular polarization (RHCP) response at 3 GHz and 7.5 GHz in the +Z direction. The experimentally verified results show -10-dB impedance bandwidth (IBW) of 40.12% (range from 2.61 GHz to 3.92 GHz) and 40.21% (range from 6 GHz to 9.02 GHz), and 3-dB ARBW are 20% (range from 2.70 GHz to 3.30 GHz) and 40.21% (range from 6 GHz to 9.02 GHz) at the resonance bands. The experimentally measured and simulated performance parameters of the prototype are in close agreement. The proposed perturbed slot radiator is well suited for Wi-Fi 6E communication and remote sensing applications.

Inverse sliding spotlight synthetic aperture radar (SAR) is not as high as sliding spotlight SAR in azimuth resolution. Its azimuth resolution is constant, and it cannot meet the needs of multiple different azimuth resolutions. In order to solve this problem, a spaceborne inverse sliding spotlight SAR for nonuniform scanned scene is proposed. The design of the proposed inverse sliding spotlight SAR includes two parts: the design of the adaptive azimuth beam steering law and the design of the imaging algorithm. In the first part, the design of the adaptive azimuth beam steering law is based on multiple specific azimuth resolution requirements and the parameters of scanned scene. In the second part, the design of the imaging algorithm for the proposed inverse sliding spotlight SAR consists of three steps: filtering processing, phase compensation and upsampling processing, and image formation. Compared with the conventional inverse sliding spotlight SAR, the proposed inverse sliding spotlight SAR can achieve different azimuth resolution requirements for scanning targets at different positions in the scanned scene. Finally, the correctness of the proposed inverse sliding spotlight SAR is verified by simulation experiment and UAV SAR experiment.

The inherent nonlinearity and ill-posedness of inverse scattering problems (ISPs) make high-quality target reconstruction challenging. To mitigate some of the difficulties and achieve more accurate and stable reconstructions, a super-resolution imaging method by use of the orbital angular momentum (OAM) wave for solving high-contrast targets is proposed. By the interaction of OAM wave and the material of target, the multiple scattering could be enhanced, and more incoherent wave could be activated. Under the frame of the contraction integral equation for inversion (CIE-I) method, the OAM-inspired CIE-I inversion method (OAM-CIE-I) is introduced to achieve super-resolution imaging of high-contrast targets. OAM electromagnetic waves, generated from a two-dimensional uniform circular array (UCA), are used as the incident field into the imaging model. Orbital angular momentum diffraction tomography (OAM-DT) is used to obtain the initial value of the contrast function containing the super-resolution information, which serves as the initial contrast value for the CIE-I model. Despite the initial contrast value differing significantly from the actual target, it contains incoherent wave information, enabling super-resolution imaging through three optimization iterations. In virtue of the inversion solver of the CIE-I, the inversion ability of the OAM-CIE-I is significantly enhanced. In the comparisons from numerical simulation results with CSI, OAM-CSI, CIE, and OAM-CIE methods, the superiority of OAM-CIE-I is demonstrated.

Wearable technologies will be extremely useful in the future life. This research proposes a textile wideband coplanar Vivaldi antenna constructed from felt substrate and two distinct types of patches, shieldit and copper tape integrated with a wearable device. This study also altered the slope of the tapered slot on the antenna's front and side to see how it affected the bandwidth and directivity antenna performance. An IoT wearable device that was connected to a microcontroller via a DS18B20 body temperature sensor and a MAX30100 sensor for heart rate and oxygen level monitoring was paired with the textile antenna. Based on the simulation findings, it was discovered that a 1 mm thick felt substrate material combined with a copper tape patch produces a workable frequency range of 2.6 GHz to 8.7 GHz, a minimum S₁₁ of -44.93 dB at 3 GHz, and a fractional bandwidth up to 107%. According to the simulation results, the antenna's side and front tapered slots have an impact on directivity and return loss. Directivity at 3 GHz can be raised by 2.63 dBi, from 1.94 dBi to 4.57 dBi, by varying the Vivaldi antenna form on both sides of the patch. The data from the sensor was successfully conveyed by combining an IoT wearable device with a textile antenna. Thus, we deduce that the textile coplanar Vivaldi antenna is appropriate for Internet of Things applications.

A novel full W-band in-line waveguide-to-suspended stripline transition based on reversed single-sided fin-line structure is proposed. To achieve wideband mode conversion and impedance matching, a combination of an asymmetric antipodal fin-line and a reversed single-sided fin-line structure is employed. The electromagnetic (EM) wave undergoes a mode transition from TE10 mode to quasi-parallel plate waveguide(Q-PPW) mode through the asymmetric antipodal fin-line. Subsequently, the mode transforms into suspended stripline mode due to the reversed single-side fin-line structure. The proposed in-line transition achieves a wide bandwidth through a simplified structural design. To assess the performance of the proposed design, a back-to-back in-line transition operating at the W-band is fabricated and measured. The measured results of the back-to-back structure demonstrate that the reflection coefficient is better than -13 dB, and the insertion loss is less than 0.54 dB across the entire W-band (75-110 GHz). The advantages of the proposed transition, such as wide bandwidth and simple structure, render it highly promising for advanced millimeter-wave circuits and systems.

Near-field scattering of human targets in the view of a bi-static, radar-like sensor operating in the lower radiofrequencies is used as an alternative to traditional biometric identification systems. These radiofrequency-based human sensor systems have emerged as a promising solution to address privacy concerns, particularly those associated with audio and visual data that extract sensitive personally identifiable information. In this paper, we propose a novel method for privacy-preserving human identification using bi-static radar-like sensors. Unlike conventional radar systems that rely on echoes and reflections in the far field, our approach is based on the transmission of signals through and around users as they pass through a transmitter and receiver. Instead of the more commonly used linear or segmented swept frequencies, this work utilizes discrete swept frequencies to transmit and receive radiofrequency signals. We have examined the performance of seven machine learning models in terms of accuracy and processing time and found that the Extra Trees ensemble model produced the best results, with an accuracy rate of 94.25\% for a sample size of 31 individuals using an Intel(R) Core(TM) i5-10300H CPU @ 2.50 GHz processor.

In this paper, a compact 2 × 1 dielectric resonator antenna (DRA) array with circular polarization (CP) agility array is presented. The array is formed of two novel resonating elements, and each is composed of a pentagonal slot (PS) coupling a rectangular dielectric resonator (RDR). The proposed resonating element emits two degenerate orthogonal modes TE_δ11^x and TE_δ21^y, confirming the CP radiation performance. The proposed resonator is utilized to portray a 2 × 1 sequentially rotated (SR) array with the ability to alter the CP polarization orientation. The signal at the feeding network input splits into two paths with equal magnitudes and phase progression phase by means of Wilkinson power divider (WPD). To obtain the 90˚ phase shifting between the WPD output signals, a single branch-line coupler (BLC) is utilized. Considering the fact that the shifting orientation of the BLC output depends on which of the two BLCs is used as in input, the signal phase at the BLC can be controlled to yield a right hand circular polarization (RHCP) or left hand circular polarization (LHCP). To control the switching between the BLC output ports phase state, two PIN diodes are used at the BLC input ports. The 50 × 50 mm² archetype achieves a bandwidth of 5.17% with a maximum realized gain of 7 dBic and a polarization purity of 4.4%. The findings of the proposed array make it a decent candidate for application using a 5.8 GHz band.

Adaptive orthogonal frequency division multiplexing (OFDM) technology is used in OFDM systems for broadband power line communications to effectively increase the communication rate. Existing research is mostly based on the single-layer network state for the resource allocation, and the required rate is often a static preset value. When there are significant differences in the signal-to-noise ratios of the sub-carriers, the system cannot adaptively adjust the required resources according to the quality-of-service (QoS) demand and the actual network, resulting in the waste of communication resources or the inability to meet some user communication needs. In this paper, a cross-layer resource allocation model is established for the system's cross-layer resource allocation problem through the data mapping among the application layer, data link layer, and physical layer. In the MAC layer, according to the quality of service (QoS) requirements of electric power multi-service, the data packet waiting delay and the packet loss are mapped to transmission rate proportionality constraints of real-time/non-real-time users through the utility function. A physical layer resource allocation model based on proportional constraints is constructed, and then an improved genetic algorithm is used for the resource allocation. Finally, through the simulation experiments in a typical power line channel environment, it is found that the proposed algorithm improves the total throughput by 4%~6% over the existing two power line carrier resource allocation algorithms under the multi-service cross-layer resource allocation, and its proportional fairness is better. The proposed algorithm is able to maximize the system capacity while ensuring the QoS requirements, effectively improving communication quality.

Faulty elements (FEs) in a two-dimensional array (TDA) directly impact the performance and configuration of the coverage pattern due to the long operation of the antenna system. Therefore, the process of dealing with these failed elements, knowing their locations, and reducing their negative impact in practice is the main goal of designing a large TDA. In this article, three types of FE locations (faulty random elements, faulty clustered elements, and faulty subarray elements) are studied. Based on the genetic algorithm (GA), the damaged coverage pattern due to the presence of these failed elements is recalculated. The method relies on re-optimizing the amplitude-only weights of non-FE optimally while neglecting the the defective elements. Therefore, the entire TDA elements do not need to be redesigned again but rather rely on the working elements only. This gives great simplification for recalculating the coverage pattern. To further control the coverage pattern in terms of the main beam width in terms of the directivity (D), the first null to null beam width (FNBW) and the sidelobe level (SLL), a fitness function is added to the optimization process under specific constraints. Simulation results for different scenarios are presented to demonstrate the validity and effectiveness of the proposed approach for dealing with FE.

This research aimed to introduce multibeam quarter-cut Radial Line Slot Array (RLSA) antennas for the first time. These antennas are distinct from the multibeam full-circle RLSA due to the use of quarter RLSA, making it suitable for small devices. To achieve beams directed to the backside, an unconventional approach was taken by placing slots on the antenna's background. A technique comprising the deletion of specific slot pairs in the radiating element was introduced to balance the gain and beam shape. Furthermore, thirty-six multibeam quarter RLSA models were designed and simulated. The best model was then fabricated and measured to validate the simulation results. Consequently, the results showed the possibility of designing multibeam antennas with symmetrical beams in terms of gain, direction, and beamwidth, which were 6.23 dBi, 37˚, 145˚, and 34˚, respectively. The gain of 6.23 dBi was 3 dB less than the single-beam antennas, consistent with the theory of beam splitting. Additionally, antennas exhibited low reflection and a broad bandwidth suitable for Wi-Fi needs. Finally, the agreement between measurement and simulation validated the design of antennas.

In the design of wireless power transfer (WPT) systems for electric vehicles, minimizing magnetic leakage while maintaining high transmission efficiency is a challenging problem. To this end, a novel structure featuring dual transmitting coils and a ring-series magnetic shielding coil (RMSDT) is proposed to reduce magnetic leakage during system charging, thereby enhancing system safety performance. Additionally, the Particle Swarm Optimization (PSO) algorithm is employed to optimize system parameters, aiming to achieve high transmission efficiency while maintaining low magnetic leakage. To validate the effectiveness of the proposed design, a shielded WPT system for electric vehicles has been developed. Its performance is verified through a combination of experiments and simulations. The results demonstrate that the PSO algorithm significantly enhances transmission efficiency compared to traditional optimization methods. At an output power of 3.7 kW, the peak transmission efficiency exceeds 95%, representing an improvement of 4.63% compared to the conventional for-loop algorithm. Furthermore, the leakage magnetic field of the RMSDT structure in the target region is only 16.08 μT, which is effectively reduced by 41.8% compared to the conventional WPT structure and sacrifices only 0.21% transmission efficiency. In summary, this paper can provide some references to the safety and efficiency of electric vehicle WPT.

Arbitrarily shaped near field with arbitrary polarization is practical application requirements. Our previous work proposed combining the phase conjugation (PC) and planar tensor impedance modulated holographic metasurface (TIMHMS) for arbitrarily shaped near field with arbitrary polarization. This paper proposes to generate arbitrarily shaped near field with arbitrary polarization by cylindrical conformal TIMHMS based on PC and Blackman window function. For the first time to the knowledge of the authors, arbitrarily shaped near field with arbitrary polarization is generated by conformal TIMHMSs. As example, two cylindrical conformal TIMHMSs are constructed at 30GHz for rectangle-shaped near field: (LHCP, z = 100 mm) and (LP, z = 200 mm), where LHCP and LP are left hand circular and linear polarizations, respectively. Blackman window function is used to optimize the cylindrical conformal TIMHMS design for optimized field pattern efficiency and low sidelobe. The calculated, simulated, and measured results agree well, and validate the proposed design method for conformal TIMHMS. The designed conformal TIMHMSs have the advantages of high pattern efficiency 42.1%, flexibly shaped field patterns and polarizations, and low sidelobe (-15 dB). The design method does not need complicated calculations and can be used in the upcoming sixth-generation wireless networks with required shaped nearfield for Radio Frequency Identification, holographic imaging, biomedical applications, etc.

Single-photon sources with high repetition rates have been a focal point of modern research for decades. However, their application in underwater environments is significantly limited due to the absorption properties of water, which hinder the propagation of most optical wavelengths. This study addresses the challenge by reporting on-demand single-photon extraction suitable for underwater quantum communication. The use of plasmonic nanoantennas can significantly enhance the spontaneous emission of single-photon sources. Nonetheless, a primary challenge is the nanoscale guiding of emitted photons in underwater environments. To overcome this, a more sophisticated design is required to enhance photon emission and achieve momentum matching with water. Here, we present a topology-optimized design of underwater plasmonic nanoantennas to mitigate these limitations. The nanoantenna consists of an optimized gold pattern and a silicon nitride substrate. Consequently, the normalized extraction decay rate (γ_e⁄γ₀) can reach 4.02 at a wavelength of 517 nm, which is within the blue-green spectral range, when using an objective lens with a numerical aperture of 0.6 (cross-section angle of 26.7°). The proposed design approach for plasmonic nanoantennas is versatile and holds promising potential for various applications, particularly in advancing single-photon technologies for quantum communication.

Brain tumors are characterized by the fast growth of aberrant brain cells, which poses a considerable risk to an adult's health since it can result in severe organ malfunction or even death. Magnetic resonance imaging (MRI) provides vital information for comprehending the nature of brain tumors, directing treatment approaches, and enhancing diagnostic precision. It displays the diversity and heterogeneity of brain tumors in terms of size, texture, and location. However, manually identifying brain tumors is a difficult and time-consuming process that could result in errors. It is proposed that an enhanced You Only Look Once version 8 (YOLOv8) model aids in mitigating the drawbacks associated with manual tumor detection, with the objective of enhancing the accuracy of brain tumor detection. The model employs the C2f_DySnakeConv module to improve the perception and discrimination of tumors. Additionally, it integrates Content-Aware ReAssembly of FEatures (CARAFE) to efficiently expand the network's receptive area to integrate more global contextual information, and Efficient Multi-Scale Attention (EMA) to improve the network's sensitivity and resolution for lesion features. According to the experimental results, the improved model performs better for brain tumor detection than both the open-source model and the original YOLOv8 model. It also achieves higher detection accuracy on the brain tumor image dataset than the original YOLOv8 model in terms of precision, recall, mAP@0.5, and mAP@0.5~0.95 above, respectively, of 2.71%, 2.34%, 2.24%, and 3.73%.

Wireless connections in 5G technology are driving the rapid growth of intelligent transport systems and vehicle communications. Wireless channels are impacted by weather, which is most noticeable in millimeter wave bands. This includes rain, fog, snow, sand, and dust. 5G networks now support diverse applications with speed and quality. In an effort to enable the use of millimeter wave frequencies, a recent study examined the impact of dust and sand on 5G channels. This paper examines the impact of heavy and frequent rainfall, along with horizontal polarization, on the propagation of millimeter waves in urban and highway settings. Using theoretical and optimization techniques, the effects of rainfall attenuation, path loss, and connection margin are evaluated at various millimeter wave frequencies. Dependencies on rainfall rate, path variation, and operating frequency are shown by the simulation results. In urban and highway situations, mean path loss and error statistics are examined with and without rainy attenuation. It is observed that the particle swarm optimization approach achieves 94% accuracy in signal propagation, which will enhance the path loss, received power and overall system performance.

A compact UWB-MIMO antenna designed for sub-6 GHz, Ku-band, and millimeter-wave applications with UWB capabilities is proposed. The antenna design consists of two inverted L-shaped MIMO elements with slot etching, deliberately positioned on an FR-4 material substrate, measuring 36 × 18 × 1.6 mm³. Utilizing inverted L-shaped elements and prudently arranged slots on the substrate, the design achieves wideband characteristics. For enhanced isolation, interconnected rectangular slots with a fork shape are etched in the bottom layer, ensuring isolation of less than -25 dB between ports. The proposed design exhibits an impedance bandwidth of approximately 54% within the frequency range of 3 GHz to 40 GHz, making it suitable for sub-6 GHz 5G bands, Ku-band, and millimeter-wave applications. The advantages of compactness and low profile of the proposed design are best suitable for 5G, Ku-band, and millimeter applications with UWB capabilities. The proposed design is successfully fabricated and tested.