This paper presents a design of a half-mode substrate integrated waveguide (HMSIW) antenna for S-band frequencies using half-octagonal ring slots to achieve significant bandwidth enhancement. The proposed structure integrates a half-octagonal ring slot within the HMSIW cavity to enhance impedance bandwidth by exciting dual resonant modes - TE₁₀₁ and TE₁₀₂. The antenna achieves a measured fractional bandwidth (FBW) of 5.6%, corresponding to an operational range of 3.15 to 3.33 GHz, and a simulated FBW of 5.2% from 3.17 to 3.40 GHz. Compared to conventional cavity-backed SIW antennas, this configuration offers a 50% size reduction while maintaining stable gain between 3.1 dBi and 5.6 dBi and exhibiting a directional linear radiation pattern in the horizontal plane. The integration of dual-resonance excitation within a single compact HMSIW cavity represents a significant advancement in bandwidth enhancement for planar antennas. This design offers a feasible and efficient solution for modern wireless applications requiring miniaturized and compact size in S-band frequencies.

Microwave non-destructive testing (NDT), with its high sensitivity and non-contact advantages, is widely applied in the defect detection of non-metallic composite materials. However, conventional microwave NDT requires frequent mechanical repositioning to modify the detection area, significantly reducing the detection efficiency. To address this limitation,this paper proposes a reconfigurable spiral defect-ground structure (DGS)-based defect scanning sensor. The sensor incorporates multiple spiral DGS units and connects them in parallel with PIN diodes. By electronically switching the state of the diodes, the location of the electric field concentration is altered, thereby controlling the sensitive detection area without mechanical movement. Compared to the existing complementary split-ring resonator (CSRR) sensors, which have a unit detection area of 3 mm × 3 mm, the proposed sensor achieves an enhanced unit detection area of 15.5 mm × 11 mm. Additionally, relying on the unique structural characteristics of the spiral shape, the field distribution is more uniform, effectively reducing blind spots in detection. Experimental results demonstrate that the proposed reconfigurable spiral DGS-based defect scanning sensor can effectively detect defects in non-metallic composite materials.

An innovative four-port Coplanar Waveguide (CPW) Multi-Input Multi-Output Antenna (MIMOA) based on a Koch Curve Fractal (KCF) with high isolation is proposed in this article. The High Frequency Structure Simulator (HFSS) is used for performance analysis and parametric optimization. Initially, a KCF-based CPW-fed single-element patch antenna is designed, which is later transformed into a four-port MIMOA (FPMIMOA). The proposed MIMOA is fabricated on an FR4 substrate and offers a wide impedance bandwidth of 1.23 GHz (4.46-5.69 GHz), centered at 4.92 GHz. It exhibits excellent diversity performance, including a Channel Capacity Loss (CCL) of less than 0.4 bits/s/Hz, an Envelope Correlation Coefficient (ECC) below 0.004, a Diversity Gain (DG) greater than 9.8, a Mean Effective Gain (MEG) below 3 dB, and a Total Active Reflection Coefficient (TARC) less than -20 dB from port 1 to the other ports. It also demonstrates an isolation level of 28 dB across the operating band. Furthermore, the proposed MIMOA achieves a high radiation efficiency (η) of 94% and a gain of 3.14 dBi. The antenna has been fabricated and experimentally tested to validate the simulated results. This MIMOA is suitable for applications such as public safety, the 5G sub-6 GHz band (4.8-5.0 GHz), and the 5.2 GHz Wireless LAN (5.15-5.35 GHz).

This paper investigates the distribution of the electric field around a circular segmented diverter strip designed for lightning protection. This is accomplished by performing parametric analysis on various geometry parameters of the circular-shaped segmented lightning diverter strip and numerically calculating the electric field and crossover voltage using full-wave simulation. The results demonstrate that as the spacing between the segments decreases, there is a significant increase in electric field strength, reaching a maximum value of 438.22 MV m^-1, while the crossover voltage decreases from 2990.59 V to 744.35 V. An increase in the diameter of the segments is associated with a stronger electric field, with the maximum field strength reaching 300.36 MV m^-1, while in this case, the crossover voltage decreases from 1493.36 V to 1462.36 V. In contrast, the electric field increases as the segment height decreases, with no significant change in the crossover voltage. The study also analyzes the impact of curvature and different substrate materials on the electric field distribution and crossover voltage. Additionally, simulation results on the electric field distribution and capacitance calculations for various segments of the diverter are utilized to predict the probable location of the lightning attachment.

An ultra-compact four-port ultra-wideband (UWB) antenna with dual notches, which can reject the 5G (3.3-4.2 GHz, 4.8-5 GHz) and the WLAN (5.15-5.825 GHz), is designed. Four orthogonal antenna elements and some defected ground planes constitute the proposed antenna. A double T-shaped filter structure is employed on the radiation unit, which can generate a notch frequency band of 3.3-4.2 GHz. The complementary split resonant ring (CSRR) structure is created on the ground plane. It is intended to suppress the frequency band from 4.8 GHz to 6 GHz by adjusting the size and position of the slots. Finally, the measured -10 dB impedance bands are 4.2-4.8 GHz and 6.0-11.0 GHz. The isolation performance exceeds 17 dB across the operational bandwidth. Additionally, the ECC remains consistently below 0.06 (and below 0.01 within the 4.2-4.8 GHz and 6.0-11.0 GHz range). Furthermore, within the operational band, the efficiency exceeds 85%. The proposed antenna is applicable in civil communication, military, and medical fields.

User-centric cell-free massive multiple-input multiple-output (UC-CFmMIMO) networks require efficient uplink power control to ensure both fairness and spectral efficiency (SE). However, existing schemes such as fractional power control (FPC) struggle to balance minimum SE and total SE, especially in large-scale deployments. To address this, we propose a grey wolf optimization (GWO)-based power control scheme, optimizing power allocation to maximize minimum SE while also improving total SE. Simulation results in a 1 km × 1 km UC-CFmMIMO network with 50 access points (APs) and 10 user equipments (UEs) show that our method outperforms FPC and fixed-point algorithm in both fairness and SE. Specifically, it achieves a minimum SE of 1.37 bit/s/Hz (vs. FPC: 0.13 bit/s/Hz) and a total SE of 39.17 bit/s/Hz at 100 APs (vs. FPC: 36.77 bit/s/Hz). The proposed approach scales effectively with AP and UE densities, making it a practical solution for future UC-CFmMIMO deployments.

In order to solve the problem of transceiver array optimization for multiple input multiple output (MIMO) radar under the conditions of fixed number of array elements and aperture length, an improved adaptive genetic algorithm is proposed in this paper. The algorithm takes the joint transceiver beam of MIMO radar as the optimization target, and optimizes the positions of the array elements of the transmitting and receiving arrays by introducing new crossover and mutation operators and elite protection strategie, which effectively reduces the number of array elements, while maintaining the main flap gain and reducing the side flap level. The effectiveness and superior optimization performance of the proposed algorithm is verified through experiments, which has certain theoretical reference significance in MIMO radar design.

In this paper, a novel single-layer dual-band metasurface MIMO antenna suitable for high-density 5G base stations, satellite terminals and IoT devices is proposed. The antenna utilizes Characteristic Mode Analysis (CMA) to optimize the patch dimensions, achieving independent design for the low and high-frequency bands. It also suppresses surface waves through a ground triple-slot structure. Additionally, the antenna abandons the traditional coplanar waveguide (CPW) and innovatively adopts an H-shaped slot feeding structure. This groundbreaking design successfully eliminates the need for complex matching networks and multi-layer stacking structures. Simulation and measurement results show that the MIMO antenna achieves an isolation below -22 dB and envelope correlation coefficient (ECC) less than 0.0025 in two operating frequency bands (4.13-5.94 GHz with a relative bandwidth of 36%; 7.6-8.4 GHz with a relative bandwidth of 10%), with a peak gain of 10.75 dB. Additionally, the antenna exhibits a diversity gain (DG) greater than 9.9 dB, with aperture efficiencies of 72% (low-frequency) and 36.8% (high-frequency). Compared with existing designs, the MIMO antenna proposed in this paper shows significant improvements in isolation, bandwidth flexibility, and structural simplicity.

Chipless Radio Frequency Identification (CRFID) systems have emerged as a cost-effective and scalable solution for various identification and tracking applications. However, multi-tag classification remains a significant challenge due to overlapping signal characteristics and the absence of on-chip processing, which hinders accurate tag differentiation, increases interference, reduces classification accuracy, and necessitates advanced signal processing techniques for reliable identification. This study presents a novel machine learning-based approach utilizing a Classifier Chain-AdaBoost (CC-AdaBoost) model to improve multi-tag classification accuracy. Unlike conventional methods that rely on calibration or background subtraction, the proposed approach directly processes raw time-domain signals, enabling efficient and accurate classification of multiple tags simultaneously. The model is evaluated on simulated CRFID data, achieving an overall accuracy of 85%. Performance metrics such as accuracy, Hamming loss, Jaccard score, and F1-score are analysed to assess both overall classification performance and label-wise evaluation. Results indicate that CC-AdaBoost effectively differentiates tag classes, particularly excelling in high-confidence classifications while maintaining a balance between precision and recall. This study demonstrates the feasibility of CC-AdaBoost for real-world CRFID applications and suggests potential improvements for optimizing multi-tag recognition in complex environments.

This paper investigates the direct detection of glucose in the visible light spectrum using a spectroscopy method. The method, which detects glucose without the need for additional enzymes or reagents, is developed using a light-emitting diode, a photodetector, and a data acquisition card (DAQ) to form a simple spectroscopy system. The system, operating at wavelengths of 505 nm, 700 nm, and 840 nm, has been experimentally tested for performance characterization. The experimental results show that the 505 nm operating wavelength produces optimal performance, with a linearity range of 20-45 mg/dL, a linearity value of 0.8812, sensitivity of 1.1 mV(mg/dL)^-1, stability precision greater than 99%, and a limit of detection (LOD) of 12.72 mg/dL. At this wavelength, the developed system improves sensitivity performance by about 69% compared to previous reports. This enhancement provides an alternative operating wavelength for glucose detection with better sensitivity performance.

In this paper, a compact and highly isolated ultra-wideband (UWB) four-port multiple-input-multiple-output (MIMO) antenna design is proposed, employing coplanar waveguide (CPW) feeding technology. The antenna system is meticulously arranged on a 0.787 mm thick RO5880 substrate, occupying a footprint of 56 mm × 56 mm (1.5λ × 1.5λ). The design comprises four identically modified antenna elements orthogonally positioned. Each element consists of an Olympic ring-shaped radiating patch within a slotted frame and two fin-shaped ground planes with E-shaped slots. Additionally, a windmill-like decoupling structure formed by rotating stubs is introduced to further enhance performance. This layout not only optimizes the isolation between antenna elements but also enhances overall performance through its unique structural design, ensuring better signal stability and wider bandwidth. The antenna system achieves an impedance bandwidth ranging from 3.65 GHz to 13.95 GHz. A thorough examination was performed on various essential MIMO performance indicators, such as envelope correlation coefficient (ECC) and total active reflection coefficient (TARC). The findings reveal that the antenna exhibits outstanding performance in these aspects, with an ECC value under 0.0012 and a TARC value under -30 dB. These results underscore the considerable potential and high performance of the proposed UWB-MIMO antenna for diverse UWB applications.

The paper presents a microwave system operating at 4-5 GHz for brain tumor diagnosis. The proposed work presents a novel method to detect the presence of tumors by capitalizing on the variations in antenna response. To achieve highly precise and fast diagnosis, a high-gain antenna is placed on the surface of the skull. The gain and directivity of the antenna are enhanced by using a Frequency selective surface (FSS) array structure placed behind the antenna which directs the energy towards the human tissues for tumor detection purposes. By using the FSS array surface, there is a 4.3 dB increase in gain and a 4.2 dB increase in directivity. Simulations are carried out using a multi-layer skull model comprising Skin, Skull, and Brain. Our proposed work demonstrates that there is a variation of about 8 dB in S-parameters when a tumor of size 6 mm × 6 mm is placed in the brain area. Further, we have investigated the S-parameter characteristics using different shapes and sizes of tumors in the brain. The results show that variation in S-parameter characteristics can potentially be used to detect the presence of tumors in the human brain.

The RCS of a composite target composed of two geometries, namely elliptical cylinder plus elliptical cone, is calculated and analyzed in this paper. To get the RCS for the target shape, the RCSs of both the elliptical cylinder and elliptical cone are calculated and analyzed before and after coating them with a designed metamaterial. Matlab and CST Simulator are used to evaluate the performance and prove the effectiveness of the metamaterial coating in reducing the RCS of the composite structure, using specially created metamaterials. This search lowered RCS across a wide frequency range of 2 to 400 GHz, which is done through specially designed metamaterials.

In order to improve the power density and torque density of the fault tolerant permanent magnet vernier rim driven machine, a new type of fault tolerant dual-permanent magnet excited vernier rim driven machine is proposed. Permanent magnets are placed on the stator and rotor of the machine, and more working harmonics are modulated by the dual-modulation effect of the air gap permeability by the teeth of the stator and rotor, thus improving the output performance of the machine. Aiming at the problem of more optimization parameters, a new optimization design method combining multi-objective genetic algorithm with single parameter scanning algorithm is proposed to optimize the design of machine. Compared with the traditional fault tolerant permanent magnet vernier rim driven machine, it shows that the machine has better output performance.

This paper presents the design of a circular-shape microstrip patch antenna structure with nine circular Electromagnetic Band Gaps (EBGs), which have been arranged in a flower shape to increase the antenna gain and be more effective in detecting metals in river prawns. Test results show that the frequency of 1.50 GHz has the greatest effect on metal detection in river prawns. The circular microstrip antenna with the EBG structure is fabricated with a copper sheet and a thickness of 0.03 cm. The radiator patch has a radius of 1.615 cm, and the EBGs, with a radius of 0.8 cm, are arranged around a circular patch antenna structure. The substrate uses a mylar polyester film sheet that has a thickness of 0.05 cm; the dielectric value is 3.2; and the impedance bandwidth of the operating frequency range is 5.26% (1.48-1.56 GHz). This proposed antenna can increase the gain up to 43.76%, with a value of 5.19 dBi. In the application for detecting metal in river prawns, the distance for placing the Tx and Rx antennas to detect metal in river prawns is 6 cm. This circular microstrip antenna can detect metals ranging from 0.5 to 3 cm and above, with an average power value ranging from -12.38 to -18.84 dBm.

With the rapid development of modern communication technologies, the use of ultra-wideband (UWB) notch antennas in various communication systems has increased significantly. However, designing UWB notch antennas with traditional methods often involves high complexity and low efficiency. To address the challenge, a novel optimization method, named BOLGB-DE (Bayesian optimization-Light Gradient Boosting Machine-Differential Evolution), is proposed. First, the BOLGB model is selected as the surrogate model to establish the relationship between antenna design parameters and performance. Then, the DE algorithm is used to invoke the BOLGB surrogate model to achieve the antenna optimization objectives. Compared to the traditional method, BOLGB-DE method enables the reduction of electromagnetic simulations by 62% (from 1176 to 440 runs) and optimization time by 62% (from 22.8 hours to 8.6 hours). Finally, a UWB dual-notch antenna is designed using the BOLGB-DE method, featuring a dual-notch structure within the 1.9 GHz-10.1 GHz range. It achieves two notch bands (3.58 GHz-4.17 GHz for C-band downlink shielding and 5.12 GHz-5.38 GHz for 5G Wi-Fi interference suppression) while maintaining the target S₁₁ values greater than -7 dB. The design requirements are successfully met by the antenna, as confirmed by the measurement results.

The increasing demand for compact, cost-effective, and versatile antennas in modern wireless communication systems has inspired research into innovative multiband antenna designs. However, numerous existing solutions are insufficient in terms of size, bandwidth, or manufacturing complexity, particularly when they aim to incorporate multiple wireless standards within a compact device. To address this gap, this study proposes a miniaturized fractal antenna design measuring 15 × 11 × 1.6 mm³, fabricated on a low-cost FR-4 substrate. The proposed antenna is inspired by nature, featuring a flower-shaped patch and a defected ground (DGS) with a spiral pattern. It exhibits multiband behavior, resonating at six distinct frequencies: 1.79 GHz, 3.84 GHz, 7.34 GHz, 9.08 GHz, 11.44 GHz, and 14.6 GHz, making it suitable for various wireless applications, including GSM/UMTS (1.7-2.1 GHz), 4G/5G and radar (3.3-4.2 GHz), military radar and satellite communications (7-8 GHz), aviation and maritime radar (8.5-10 GHz), satellite communication in the Ku-band (10.7-12.7 GHz), and advanced radar and satellite uplinks (12-14 GHz). The fabricated antenna was tested, and the experimental results demonstrated a strong correlation with the simulated outcomes, confirming its practical applicability and effectiveness in multiband communication systems. The proposed fractal antenna stands out due to its compact size, multiband capability, and excellent performance, making it well suited for modern wireless applications.

With the growing use of radar sensors, particularly in surveillance applications, there is an increasing need for real-time target tracking, especially in areas such as counting people. This paper offers a detailed description of the hardware setup, which is paired with a proposed fusion algorithm and the multiple-target tracking (MTT) algorithm for online target tracking. The fusion techniques introduced in this work combine data from spatially distributed Texas Instruments mmWave radar sensors by utilizing the likelihood of radar measurements. These sensors measure the positions of the reflectors, which are then visualized through the Robot Operating System (ROS). To support real-time target tracking and people counting, a connection is established between the ROS network and MATLAB. Finally, the measurements are processed in MATLAB using the proposed fusion technique alongside the existing MTT algorithm to generate accurate target tracks, which also enable people counting.

Primary insertion phase delay (IPD) expression is obtained using the flat plate model with plane wave incidence, and it only considers the longitudinal phase shift in the free space. This causes errors in large curvature radome applications since the longitudinal distance that wave travels in flat plate cannot represent the actual distance. Therefore, the IPD expression for radomes with large curvature should be defined. Based on the ray tracing in the radome medium, a modified IPD expression with more accurate transmission distance for large curvature radomes is proposed. The proposed expression can be applied to radomes with arbitrary curvature. The correctness of our proposed expression is verified via a simplified fast radome analytical model. The results from the proposed expression show errors within 1.0° for the parabolic radome system. The proposed expression can be applied to optimize the performance of radome systems with large curvature. A reflector antenna radome system is employed for verification. Results show that using the modified IPD expression to optimize the reflector antenna can increase the system gain by 1.8 dB, reduce the side lobe by 7.6 dB, and narrow the beamwidth by 0.9°.

With the increasing interest in negative group delay (NGD) function for RF and microwave circuits, and sensing applications, techniques to fit multiple NGD bands in a single and compact structure can open new possibilities. In this work, a simple and innovative compact quadband NGD microstrip circuit is presented for all ISM bands between 2 GHz and 6 GHz. The circuit is composed of a base line (BL) coupled to the transmission line, which sets the lowest NGD band, and each additional NGD band is created by inserting stubs into the BL. The impact of each stub on the overall circuit is analyzed using parametric simulation. The design and tuning method of the coupled line used to achieve the NGD multiband function is described in detail. Through the insertion loss and group delay results, a well-fitted correlation is observed between the simulated and measured results, where the simulated transmission coefficient and group delay show NGD quadband response with center frequencies at 2.46, 3.49, 4.96, and 5.69 GHz with respective NGD bandwidth of 0.89%, 0.83%, 0.66%, and 0.97%, respectively, whereas the measured results present center frequency NGD deviation of less than 1%. In addition, the NGD quadband circuit prototype has a compact size 40.2 × 30.2 × 1.57 mm³. The measured NGD results are in good agreement with simulated ones.