This article introduces a compact design for a four-element MIMO antenna for millimeter-wave (mmWave) communications for specifically n261 band having range from 27.5 GHz to 28.35 GHz with a bandwidth of 850 MHz. The single antenna structure uses a rectangular patch having four diamond-shaped slots in the feed-plane. On the ground plane, a dumbbell-shaped slot is positioned below the rectangular patch. A Rogers RT/Duroid 5880 substrate with ultra-thin thickness is used in this design. The optimized design for four-port MIMO antenna has small size with dimensions of 20 mm × 19 mm × 0.254 mm. The MIMO parameters such ECC is less than 0.011, and DG is greater than 9.90 dB in the mentioned band, which are within tolerance limits. The isolation between neighbouring MIMO elements is also less than -19.5 dB.

This work investigates low-power electromagnetic energy harvesting at 2.4 GHz and 5 GHz using an elementary rectangular patch rectenna along with a step-up DC-DC boost converter. The receiving antenna is optimized to 50 Ω impedance by tuning parasitic ground plane stubs in the resonating frequencies. The return loss and gain of the proposed antenna are -30.19 dB, -31.02 dB and 2.45 dBi, 4.84 dBi at 2.4 GHz and 5 GHz respectively. A single-stage Greinacher voltage multiplier with a compact dual-band pi-model matching circuit is proposed as a rectifier. The rectenna is manufactured on an FR4 substrate, and the measured performance is in good agreement with the simulated results. The transformation efficiency of more than 40% is noticed in the wide input-power range from -12 dBm to 5 dBm. The maximum efficiency of 50% and DC output voltage of 1.57 V at 0 dBm input power with 5.1 KΩ optimized load resistance is noticed when the RF source and rectenna are 46 cm apart. The proposed rectenna with a DC-DC boost converter can drive the LED indicator and wall clock simultaneously. The prototype rectenna is suitable for energizing low-power sensor nodes in IOT and WSN applications.

Quantum emitters coupled to plasmonic nanostructures can act as extremely bright single-photon sources. Interestingly, the mode volumes supported by the plasmonic nanostructures can be several orders of magnitude smaller than the cubic wavelength, which leads to dramatically enhanced light-matter interactions and drastically increased photon emission. However, the requirements of a small mode volume for emission speed-up are always contradictory with a sufficiently large mode volume for efficient extraction, especially in a single architecture. Here, we report the design of a topology-optimized plasmonic nanoantenna to alleviate the above limitation which could greatly enhance far-field photon extraction. The plasmonic nanoantenna is composed of an optimized gold pattern and a silicon nitride substrate, with a nanohole in the center of the gold pattern. Our design is based on density-based topology optimization and is inherently robust to dimensions and fabrication errors. As a result, the normalized extraction decay rate (γ_e⁄γ₀) can reach 5.48 at a wavelength of 517 nm if an objective lens with a numerical aperture of 0.45 is utilized. Plasmonic nanostructures can be obtained with a small mode volume of about 5 × 10^-21 m³, while emission speed-up could still be achieved. The proposed method to alleviate the contradiction of plasmonic mode volume could brighten the prospects for future integration of single-photon sources into photonic quantum networks and applications in quantum information science.

To reduce large torque ripple in permanent magnet-assisted switched reluctance motors (PMa-SRMs), a novel direct instantaneous torque control (DITC) strategy with zero-voltage modulation is proposed in this paper, where a fixed-frequency pulse width modulation (PWM) is replaced by the conventional DITC hysteresis controller to optimize zero-voltage insertion time through zero-voltage decentralized modulation to minimize switching losses. Control intervals are then divided based on inductance and torque-to-current ratio (TCR) characteristics, with adaptive duty cycle adjustments to enhance torque tracking and reduce ripple. Additionally, the optimal turn-on and turn-off angles are determined by the dung-beetle-optimized back propagation (BP) neural network (DBO-BP) algorithm, which suppresses the torque ripple, lowers phase current peaks, and improves motor efficiency. The feasibility and effectiveness of the proposed method are validated by simulations and experiments with a three-phase 6/20 PMa-SRM.

Conventionally, the thinning process in antenna arrays was performed at the element level with random selection after examining all the possible combinations. Thus, the computational time of such thinned methods was relatively high. Reducing the undesirable high computational time is of great interest. In this paper, the thinning process is performed at subarray level rather than element level, thus, the computational time and array complexity were significantly reduced while minimizing the peak side lobe level (PSLL). The optimization process consists of two steps where in the first step the array elements are portioned into a number of nonuniform ascending subarrays, while in the second step some of the least significant subarrays were turned off. Moreover, two schemes were used to portion the array elements. The first one is based on portioning all the array elements into ascending subarrays. This is known as fully nonuniform ascending subarray configuration since the entire array elements were portioned into smaller unequal groups. The second one is based on portioning only part of the elements located at the sides of the array, while leaving the central elements individually without any partition. This is known as partially nonuniform ascending subarray configuration. The genetic optimization algorithm is used to find out optimally which subarrays need to be thinned (or turned off) by setting their excitation amplitudes to zero. The simulation results for a total of 100 elements linear array illustrate that the PSLL, in the full subarray configuration, can be minimized to more than -33 dB by thinning 5 subarrays and the complexity reduction percentage was 72% before thinning and it becomes 82% after thinning. On the other hand, the PSLL in the partial subarray configuration was reduced down to more than -30 dB by thinning 4 subarrays at each side of the array. In this case. The complexity reduction percentage was 52% before thinning, and it becomes 60% after thinning. The number of individual central-elements on both sides of the array was 26, and the number of subarrays on both sides of the array was 22. Furthermore, the idea of the thinned subarrays was successfully extended and applied to the two-dimensional planar arrays of 100 × 100 elements.

This work explores the potential of spoof surface plasmon polaritons (SSPPs) for effectively feeding high-frequency antennas operating in the extremely high-frequency (EHF) range. An innovative approach is introduced in this study to utilize SSPP to feed a dielectric rod antenna. The design incorporates a straightforward dielectric rod antenna fabricated using FR-4 material with a relative permittivity of 4.3. Compared to conventional tapered dielectric rod antennas and their corresponding feeding configurations, this design presents the potential benefit of achieving an improved gain of up to 16.85 dBi using a specific antenna length of 7.6λ₀. Through careful design optimization, we achieved impedance matching and directional radiation characteristics at a frequency of 7.3 GHz. To validate our design and assess its performance, we conducted simulations using the CST Microwave Studio. This study aims to demonstrate the effectiveness and practicality of the proposed dielectric rod antenna with an SSPP feed.

This paper proposes a variable flux leakage permanent magnet (PM) machine and investigates the impact of slot and pole number combinations on the electromagnetic performance of a variable flux leakage permanent magnet machine (VFL-PMM). The stator armature winding dq-axis magnetic circuit is designed to couple with the PM leakage magnetic circuit by the deliberate establishment of a leakage-guided magnetic barrier and a poly-magnetic barrier on the rotor side. The VFL-PMM with 12s10p-DL (double layers) fractional slot centralized winding (FSCW) serves as an illustrative example of global parametric modelling of the machine. The objective is to optimize the split ratio, average torque, torque ripple, and PM utilization of the machine to obtain the optimum amount of the machine. The relationship between the no-load, on-load characteristics, and variable flux leakage characteristics of 12s8p, 12s10p, 12s14p with double-layer FSCW and 12s10p with single-layer FSCW are studied comparatively. The machines are analyzed and optimized using 2D finite element analysis.

In this paper, a novel stacked wideband differentially feed antenna with dual polarizations is designed for base station. The circular parasitic patch deepens the resonance depth by slotting. Two linear dipoles are placed at ±45° under the circular parasitic patch to reduce the overall size of the antenna. The antenna introduces a cross-shaped differential feed to achieve high port isolation. Finally, the designed antenna is fabricated and tested. The test results show that the differential reflection coefficient |Sdd11| is more than 15 dB. The antenna achieves a differential impedance bandwidth of 53.1% (1.63 GHz-2.8 GHz). The isolation is greater than 42 dB over the entire operating bandwidth. The antenna also has a stable gain of 8.2±0.4 dBi and a half-power beamwidth of 65°±4°.

To address the issues of high current harmonic and power ripple in the traditional Finite Control Set Model Predictive Control (FCS-MPC) strategy for virtual synchronous generator system with quasi-Z-source inverter (qZSI-VSG), a double and triple-vector hybrid modulation model predictive control strategy is proposed. This strategy utilizes the inductor current sub-cost function to select the shoot-through state (ST state) or the non-shoot-through state (NST state). When NST state is selected, the voltage vector combinations in the double-vector and the triple-vector are initially established. Then, the voltage vector combinations are reduced from 18 groups to 6 groups by using the vector combination quick selection table. Subsequently, the duty cycle of each voltage vector is then determined based on the value of its cost function, and the voltage vector is re-synthesized. Finally, the predicted values of all control variables are calculated and substituted into the cost function for optimization. Experimental results show that the proposed strategy reduces 48.62% of current harmonic, 50% of active power ripple and 25.53% of capacitor voltage ripple compared to the traditional strategy, which effectively improves the system control performance.

In order to effectively reduce the loss of the filter, decrease its size, and improve its frequency selectivity, a miniature filter unit has been proposed. This unit offers enhanced frequency selectivity and facilitates adjustment of the center frequency. The filter unit is constructed by embedding a serpentine microstrip resonator in the upper metallic surface of a half-mode substrate-integrated waveguide (HMSIW). The center frequency of the filter unit is considerably lower than the cutoff frequency of the HMSIW, which contributes to the miniaturization of the filter. The center frequency of the filter unit can be adjusted solely by modifying the dimensions of the microstrip resonator, while the dimensions of the remaining components can be maintained at a constant value. A transmission zero has been incorporated into the upper resistance band with the objective of enhancing its frequency selectivity. A second-order filter with a center frequency of 3 GHz is accurately designed using this filter unit. The results demonstrate that a miniaturized filter with the desired center frequency and excellent performance can be rapidly achieved using this filter unit, which has potential applications in the 5G (sub-6G) band.

Optical materials whose permittivity becomes negative for certain wavelength ranges, so-called plasmonic materials, have been widely used for biochemical sensing applications to detect a wide variety of analytes from chemical agents to protein biomarkers. Since many analytes are or contain nanoscale objects, they interact very weakly with light. Thus, light confinement is a key to improving sensitivity. Using metal or plasmonic nanostructures is a natural solution to confine light and boost light-matter interactions. As there are several different optical sensing schemes, such as refractometric sensing, fluorescence-labeled sensing, and vibrational spectroscopy, whose operating wavelength spans from ultraviolet to mid-infrared wavelength regions, some plasmonic materials are superior to others for certain wavelength regions. In this article, we review current progress on alternative plasmonic materials, other than gold, silver, and aluminum, used in biochemical sensing applications. We cover a wide variety of plasmonic material platforms, such as transparent conductive oxides, nitrides, doped semiconductors, polar materials, two-dimensional, van der Waals materials, transition metal dichalcogenides, and plasmonic materials for ultraviolet wavelengths.

In order to meet the current demand for 5G smartphone antennas, this paper introduces a six-port dual-band multiple-input multiple-output (MIMO) antenna designed for 5G smartphones. Based on multimode, the antenna achieves multiple band coverage in a limited space, making it of significant practical value in 5G cell phone antenna applications. The antenna features a structure comprising a modified L-shaped patch antenna, a gun-shaped slot in the ground plane, and two small stubs extending from the metal ground. This configuration creates a multimode antenna that is excited by two coupled feed loop modes and two slot modes. The feeder strips, which have been enhanced with L-shaped slots, form tuned branches, enabling the co-excitation of multiple modes. The MIMO system can operate within the frequency range of 3.3-3.8 GHz and 4.4-7.5 GHz (S₁₁ < -6 dB), covering the 5G communication bands including n78 (3.3-3.8 GHz)/n79 (4.4-5.0 GHz) and the LTE Band 46 (5.15-5.925 GHz). Additionally, the antenna exhibits an envelope correlation coefficient of less than 0.18, antenna efficiency ranging from 60% to 93%, and isolation between adjacent antenna elements better than 12.9 dB.

Sparse arrays have the technical advantages of large equivalent aperture, high degrees of freedom (DOFs), and low mutual coupling leakage. In this article, a novel symmetric sparse array, termed as symmetric shifted coprime array (SSCA), is proposed for the localization of both the far field and near-field of sources. It can be generated in two steps. Firstly, the second subarray of the traditional coprime array is shifted by a appropriate distance, and secondly, the entire array is flipped. By translating, the proposed array provides increased DOFs and enhanced ability to resist heavy levels of mutual coupling. Meanwhile, the symmetric structure of the array can be ensured by flipping to solve the parameter estimation of mixed fields. We provide an analytical expression for the proposed array and also derive its DOFs and weight functions. The first three weight functions of SSCA are equal to 2, indicating that the SSCA improves the ability to resist mutual coupling. Numerical results show that the proposed array is superior to existing sparse arrays for both direction of arrival (DOA) and range estimations.

Conventional hairpin band-pass filters (BPFs) typically have poor stopband performances. Therefore, this paper proposes a BPF with a center frequency of 24 GHz that employs a novel hairpin-coupled structure. An enhanced hairpin-coupled resonator topology is also introduced to improve the stopband suppression characteristics. Specifically, the proposed resonator and filter are configured through a hairpin structure and source-third resonator coupling, which afford a miniaturized size and coupling of the transmission zeros. Then, an equivalent circuit model is simulated to conduct loss analysis of the millimeter-wave (mm-wave) BPF, and the corresponding analytical parameters and result data are extracted. Furthermore, fast synthesis is achieved for the high stopband suppression mm-wave filter. The compact BPF developed is fabricated using the quart glass process, with the corresponding measurements revealing that the insertion Loss (IL) is less than 4.5 dB, and the return loss (RL) exceeds 9 dB within the passband. Meanwhile, the stopband suppression at 20.6 GHz and 28.6 GHz can reach 43 dB and 35 dB, respectively. Those advanced performances demonstrate the promising prospect of the proposed filter for its application in biological radar life feature monitoring.

A compact ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with four stopbands is designed and experimentally investigated. By the method of coating, various T-shaped structures and split-ring resonators (SRRs) are used for suppressing the mutual coupling and introducing the band-notched characteristics, respectively. The actual design has an overall size of 46 × 37 × 1.57 mm³ across the whole UWB spectrum from 2 to 22 GHz except stopbands from 3.47 to 3.83 GHz, 5.2 to 5.85 GHz, 7.19 to 7.84 GHz, and 8.15 to 8.6 GHz, which prevent the interference of Microwave Access (WiMax), wireless local area network (WLAN), satellite downlink and satellite communications band (ITU 8 GHz) bands, respectively. Besides, the isolation of the most operating frequencies is higher than 20 dB, and the antenna obtains a fairly stable radiation pattern and gain, as well as a lower envelope correlation coefficient (ECC < 0.005). Additionally, using the antenna inserted in name badge of the doctor, the chance of infection will be greatly reduced. Ultimately, the proposed MIMO monopole antenna has a potential application in the medical domain.

Communication blackout is a serious threat to aerospace engineering. Over the past decade, the terahertz (THz) technology has been considered an effective solution to the blackout problem. However, it is currently unclear that how the size of the vehicle affects the conditions of the THz communication channel within the plasma sheath. In this study, a numerical hypersonic hydradynamical model is introduced to investigate the relationship between THz signal attenuation in the plasma sheaths and the size of the vehicle. The analysis shows that the size of the vehicle significantly influences the structure of the plasma sheath. The thickness of the plasma sheath increases linearly with the size of the vehicle. The maximum electron density in smaller vehicles shows unstable fluctuations, attributed to variations in size causing changes in the flow velocity and mass density, resulting in the variation of pressure distribution. Additionally, with the increase of plasma sheath thickness, the attenuation coefficient of THz signals increases linearly. Therefore, for the vehicles of large sizes, the designs that minimize the thickness of the plasma sheath, such as shaped configurations, are helpful to mitigate the communication blackout.

This paper presents a compact 3-port multiple-input multiple-output (MIMO) antenna for 5G wireless communication, covering the 2.6 GHz, 3.5 GHz, and 4.8 GHz bands. Three orthogonal modes (TMsub>10, TMsub>01, and TMsub>20 modes) are excited to realize tri-band operation and high isolation simultaneously. Using characteristic mode analysis (CMA), dual-slot structures and I-shaped patches are introduced to block coupling path, and the isolation is improved. Simulated and measured results show that the proposed antenna operates in the frequency bands of 2.57 to 2.64 GHz, 3.4 to 3.5 GHz, and 4.8 to 4.9 GHz with isolation better than 20.6 dB. In addition, it can be calculated that Envelope Correlation Coefficient (ECC) (<0.06), Diversity Gain (DG) (>9.99 dB), Total Active Reflection Coefficient (TARC) (<-10 dB), and Channel Capacity Loss (CCL) (<0.45 bits/Hz/sec) are in acceptable level, implying excellent diversity performance and data transmission quality. It is worth noting that the evolution of the antenna is entirely based on the CMA, which greatly simplifies the design process. The antenna has the advantages of high isolation, compact structure, easy processing, and low cost, positioning it as a compelling candidate for integration into 5G wireless communication systems.

This paper addresses the high-frequency signal transmission problem of high-speed differential lines on four-layer printed circuit boards (PCBs). It establishes a mathematical model of high-speed differential lines in conjunction with modified Kron's methodology (MKM), a nontraditional circuit modeling method. The article builds the model through diakoptics of differential lines, then generates the corresponding topology maps, and finally creates the model through tensorial analysis of the network (TAN). The differential line model is simulated and optimized by HFSS. This paper mainly analyzes the influence of differential line spacing and grounding vias on the signal transmission of differential lines. Secondly, it analyzes the problem of multi-group differential line arrangement based on the above work. Finally, the experimental results obtained are consistent with the simulation ones.

In this paper, a novel decoupling strategy for a MIMO antenna is proposed. This MIMO antenna system consists of two symmetric inverted L shaped antenna elements. To improve the isolation between radiating antenna elements, split ring arrays, neutralisation line and ground slots are employed. The MIMO antenna operates at 6.27 GHz. Neautralization line aids in cancelling the coupling by introducing reverse coupling. Ground slots introduce band-stop characteristic to nullify the coupling effect, and split ring array blocks the electromagnetic coupling reaching the other antenna element. The isolation parameters |S₁₂| and S₂₁ obtained are less than -21 dB. The diversity parameters envelope correlation coefficient and diversity gain are investigated. Envelope correlation coefficient is within acceptable limit. These diversity parameters indicate that good diversity performance is achieved by the proposed MIMO antenna. Measured results are in good agreement with simulated ones. The suggested antenna is appropriate for many wireless applications, including IEEE 802.11 and 802.16 standards, as we deal with the sensitive environment.

Wireless power charging technology has been developed rapidly and is extensively utilized for electric vehicle wireless charging due to its numerous over plug-in charging. The electromagnetic bio-safety of the human body in charging environment has become a significant public concern. To address this issue, this paper employes the finite element analysis method to assess the electromagnetic safety of crucial organs in a typical charging environment. Firstly, human-vehicle models in various typical postures were constructed in COMSOL, and the spatial distribution of electromagnetic fields in the critical organs was calculated in a 7.7 kW, 85 kHz charging environment. Subsequently, the electromagnetic radiation dose of each organ was calculated and compared with the ICNIRP standards. The results indicated that the electromagnetic radiation dose received by different organs is influenced by both the electromagnetic parameters and position of the organs. When the human body is positioned flat in the car, the electromagnetic radiation exposure to various organs is at its highest. Additionally, the maximum radiation dose for each organ is significantly below ICNIRP standard in a low-power wireless charging environment, supporting the commercial adoption of wireless charging technology for electric vehicles.