An eddy current damper for an optimized rotation magnetized direction (RMD) permanent magnet thrust bearing (PMTB) was analyzed in this paper. Initially, optimization of critical design variables was performed for a particular bearing volume for maximum force as well as stiffness. Then, generalized curve fit equations were established to obtain a correlation between different geometrical parameters concerning the outer diameter and airgap. Furthermore, the axial force of the optimized RMD configuration calculated using mathematical model was validated using the results of FEA in ANSYS. Finally, finite element simulation was performed to evaluate the damping forces generated by an eddy current damper (ECD) for an optimized thrust bearing. Analysis has shown that eddy current dampers can improve system damping.

Wideband designs of a U-slot cut square microstrip antenna using bow-tie and H-shape ground plane profiles are proposed on an electrically thinner substrate. The modified ground plane optimizes the input impedance at patch resonant modes on the thinner substrate, which yields wider bandwidth. Against the conventional ground plane design on substrate thickness > 0.06λ_g, the bow-tie shape ground plane offers 0.03λ_g reduction in total substrate thickness, 10% increment in the bandwidth with a peak broadside gain of 6.1 dBi. The design methodology to realize a similar configuration as per a specific frequency spectrum is presented, which yields similar response.

This article proposes an approximate analytical formulation to calculate the low-frequency magnetic shielding of a rectangular metallic box, with all walls perforated periodical holes. The solution is obtained by the combination of two submodels: the finite conductivity box with the holes covered and the perfect conductor box with the holes present. The first submodel represents the diffusion effect of magnetic field penetration through the conducting shell, and the second one denotes the aperture effect of magnetic field leakage through the holes. The total shielded magnetic field is the superposition of these from the two submodels. For the diffusion effect, an existing empirical formula based on the shape factor is used. To solve the second submodel, we employ two approximate methods: the method of images and the surface-impedance method. The method of images models each hole in the walls as an equivalent magnetic dipole and its images based on Bethe's small aperture coupling theory. A PEC box is first considered. Comparisons with finite element simulations show that the method of images has better accuracy than the surface-impedance method. Then, a cubic aluminum box of 0.2 m in length is treated, which verifies that combining the two submodels can produce results in good agreement with finite element simulations for frequencies up to 10 MHz. In addition, the dependence of the shielding effectiveness on frequency is also analyzed.

An original application of stopband (SB) type negative group delay (NGD) electronic function is introduced. The unfamiliar SB-NGD circuit is designed with RLC-network lumped passive topology. The SB-NGD circuit is exploited to operate as a true-time delay (TTD) device for smart dual-beam phased array design. The two-port passive topology for designing an SB-NGD circuit constituted by an RLC-network is described. The theory and design method of the employed SB-NGD passive circuit are detailed. The microwave theory of the SB-NGD topology is elaborated from S-matrix modelling. The SB-NGD canonical form is innovatively introduced in function of the expected specifications. The synthesis design equations allowing to determine the R, L and C component values in function of the NGD specifications are formulated. The SB-NGD behavior is verified by comparison of calculated and simulated S-parameters from two different proofs-of-concept (POC). Illustrative results with a very good agreement showing SB-NGD behavior are observed around the arbitrarily chosen central frequencies f₁ = 0.7 GHz and f₂ = 1 GHz over a bandwidth of 50 MHz. The design principle of TTD-based smart dual-beam is described. The dual-band SB-NGD circuit is designed to operate as a dual-band TTD device with fixed delays at t₁(f₁) = 357 ps and t₂(f₂) = 875 ps, respectively. A radiation pattern showing the smart dual-beam steering operating system at f₁ and f₂ frequencies is discussed.

In recent years, topological states in photonic artificial structures have attracted great attention due to their robustness against certain disorders and perturbations. To readily understand the underlying principles, topological edge modes in one-dimensional (1D) system have been widely investigated, which bring aboutthe discovery of novel optical phenomena and devices. In this article, we review our recent advances in topological edge modes. We introduce the connection between topological orders and effective electromagnetic parameters of photonic artificial structures in band gaps, discuss experimental demonstration of robust topological modes and their potential applications in wireless power transfer, sensing and field of optics, and give a brief introduction of future opportunities in 1D topological photonics.

This paper proposes a novel asymmetric interior stator topology for torque enhancement and torque ripple reduction in external rotor switched reluctance motor (ERSRM). The new topology and operational principle are first investigated using a simplified linear model. Then, the parametric model of the ERSRM and the comprehensive sensitive analysis that evaluates the influence of each design variable on optimization objectives are presented. Thirdly, the optimal design is selected from the Pareto front which is generated by NSGA-II (fast non-dominated sorting genetic algorithm) and validated by finite element analysis. Finally, the optimal prototype motor is manufactured, and experimental results confirm the validity and superiority of the optimized design.

This paper presents an alternative solution for detecting breast cancer through planar antennas. The designed antenna electric parameters are the best gain for tiny radiation elements, along with the suitable characteristic impedance and bandwidth focusing on a specific application. Antennas are deployed nowadays to provide access to the detection of malignant tumors. That solution coexists with those in the hospitals (X-ray Mammography, Biopsy, Ultrasound, and Tomography), as breast cancer is a worldwide health concern because many women die yearly. Unfortunately, none of these methods are efficient as microwave imaging techniques. In terms of rapidity, efficiency, sensitivity, and accuracy, a small microstrip patch antenna operating at the Industrial, Scientific, Medical (ISM) band (5.72-5.82 GHz) is proposed in this paper for early breast tumor screening. Designed from the High-Frequency Structure Simulator (HFSS), the rectangular microstrip patch-antenna of 12x12x1 mm³, etched on an FR4 HTG-175 dielectric material (relative permittivity of 4.4 and 0.02 of loss tangent) has been simulated, prototyped, and experimentally measured with ZVA50 Vector Network Analyzer (VNA). The defective ground structure technique has been used to achieve the goals of the final prototype. The proposed antenna has 51.22 dB of return loss, 230 MHz of bandwidth, with a radiation efficiency of 82% and a gain of 1.45 dBi at the resonance frequency of 5.73 GHz. Simulation results have been well-concluded through different tumor positions on the breast to take comprehensive precautions. Furthermore, a comparison with other antenna designs has been made. Due to the available laboratory equipment, the suggested work focused on the research part.

A high-efficiency interaction circuit for Ka-band klystron has been proposed based on a novel internal coupling cavity. Driven by a 25 kV, 5 A pencil beam, the interaction circuit can produce a peak output power of 38.4 kW at Ka-band, and the electronic efficiency is 30.7%. The electromagnetic properties of the unequal slot multi-gap cavity and internal coupling cavity have been studied and compared. The internal coupling cavity demonstrated a higher coupling coefficient and characteristic impedance than the unequal slot multi-gap cavity, which can improve the circuit efficiency. Stability and pattern analysis have been performed on the output cavity. A four-gap output cavity has been designed. Simulation results show that there is no mode competition and oscillation in the output cavity. The corresponding beam optics has also been designed to produce the required beam. Compared with the existing work, the interaction circuit can produce almost twice the output power with the same beam voltage and Brillouin focusing magnetic field. The efficiency is also improved by 6 percent.

This article proposes a 4-port MIMO antenna for 5G mid band application resonating from 4.5-5.1 GHz which comes under n79 band, an FR1 5G NR band used in smart phones. The first design involves a single-element microstrip patch antenna with a diamond shaped slots and partial ground structure of size 30 × 43 × 1.6 mm³. Using this single element antenna as reference, a 4 port MIMO antenna is presented which operates at 4.9 GHz resonance frequency with proper spacing, resulting in much improved isolation between the elements. The proposed 4 port MIMO antenna is designed and fabricated over a commercially available low-cost FR-4 substrate having a relative dielectric permittivity of 4.4 and thickness of 1.6 mm. The W × L dimension of this MIMO antenna is 56 × 56 mm². Simulation of the S-parameters and radiation pattern of all purposed designs is performed using the CST studio suite, and test results of the return loss are presented using the Keysight N9916A 14 GHz vector network analyzer. Antenna gain is 3.8 dB, and efficiency is 87% with a low (less than 0.1) envelope correlation coefficient (ECC) between any two radiating elements, paired with a positive diversity gain (DG), indicating that the proposed antenna is well designed. As a result, the proposed antenna is an excellent candidate for deployment in 5G networks.

We study three comb-line antennas to increase the bandwidth for a 3 dB axial ratio criterion. Each antenna comprises linear radiation elements with loops and a coplanar feedline above the ground plane. First, we analyze a reference antenna with a straight feedline using the method of moments. Next, the straight feedline is transformed into a round one for a sequential rotation technique. It is found that the antenna has an increased bandwidth of 30%, which is three times as wide as that of the reference antenna. Last, we propose a novel antenna with a straight feedline. It is revealed that the antenna shows a 3 dB gain drop bandwidth of 29% (40% for the axial ratio bandwidth). The simulated results are validated by experimental work.

A rigorous solution is presented for description of the plane electromagnetic wave diffraction by two parallel slots in a perfectly conducting screen of finite thickness, placed before a dielectric layer, operating as a receiver of radiation in the near zone. The field in this layer is studied for the case of small obstacle dimensions being of the order of the wavelength. It is shown that the best spatial resolution of images from two slots in a dielectric layer is reached together with their optimal focusing, which can be determined by the method proposed earlier for one-slot diffraction.

This paper demonstrates a compact two-port multi-input multi-output optical nano-antenna with polarization diversity. The proposed antenna consists of a silicon-based radiating element that explores the possibilities of using a highly efficient dielectric resonator over the conventional metallic antennas at THz regime The specific position of the Gaussian pulse excitation generates the 90° phase difference between the field components travelling across the edges of the silver nanostrip feedlines. This generates the orthogonal field components which results in the achievement of circular polarization. Furthermore, any deviation in the excitation position at the port disturbs the field components resulting in linear polarization. This approach provides the polarization diversity using different excitation positions at ports. Considering the analytical stage of this proposed work, the detailed design guidelines and analysis are also discussed. The antenna provides circularly polarized radiations having 6.78% of 3 dB axial-ratio bandwidth and linearly polarized response using the optimized feeding positions at the respective ports for obtaining the polarization diversity performance. The isolation of more than 15 dB is maintained between the ports over the entire operating passband of the antenna. The proposed antenna with the optimized dimensions can be utilized for the optical C- and L-band applications.

For the research of 5G NR band mobile phone bezel antenna, this paper proposes an 8-Element Multiple-Input Multiple-Output (MIMO) handset bezel antenna design for 5G New Radio (5G NR) bands. Moreover, the MIMO antenna's array is implemented by loading 8 identical antennas (Ant1-Ant8) into the metal bezel of the smartphone to form an 8-antenna array for a sub-6 GHz 8×8 MIMO system. In this setting, each antenna unit is a slot antenna type consisting of a Chinese character ``卫''-shaped slot, as well as a 50 Ω micro-strip feeder; note that a satisfactory impedance matching is achievable in the upper-frequency band by loading a tuning stub on the feeder. The proposed 8-element antenna array covers 5G new radio (NR) band including N77 (3.3-4.2 GHz), N78 (3.3-3.8 GHz), N79 (4.4-5.0 GHz), and a Wi-Fi (2.4 GHz) band with a 10 dB impedance bandwidth. It is important to note that in addition to exhibiting ideal antenna efficiency and envelope correlation, the isolation between adjacent array elements is >10 dB, and the peak gain is 3 dBi. In summary, the influence of the user's hand on the antenna is analyzed to ensure the robustness of the MIMO antenna system in practical applications.

Thinner substrate designs of square and circular microstrip antennas using fractal variations of U-shape and half U-shape slot cut ground plane are proposed for circularly polarized response. The 1st, 2nd, and 3rd order fractal variations of slots on the ground plane are studied. The fractal slot cut variations degenerate patch fundamental mode into dual orthogonal resonant modes, and an optimum spacing between them yields circularly polarized characteristics. Amongst all the designs, circular microstrip antenna using the 1st order fractal U-slot design yields optimum result. It offers axial ratio bandwidth of 60 MHz (2.14%) with a broadside radiation pattern and peak gain of 5.5 dBi, on a substrate of 0.02λ_g thickness and patch area 1.44λ_g. Against the reported designs, the current work presents a low profile single patch circularly polarized configuration.

This study presents the generation of a scalable model based on measurement aided numerical calculations for MiMCap (Metal-Insulator-Metal Capacitor) structures with a 0.25 µm SiGe-C BiCMOS technology. Various MiM capacitor structures with several different area and peripheral sizes are fabricated in an in-house developed BiCMOS process. A set of fix-size models and a generic scalable model are developed based on numerical EM calculations. The validity of the constructed model is verified with the measurement results. The model includes the breakdown voltage ratings which are also extracted through the measurements. The model, EM simulations and measurement results are in good agreement.

This paper presents a new compact dual-band bandpass filter (BPF) with a stub-loaded resonator structure that can independently change its operating band to support GSM and WiFi applications for modern wireless communications. A short-circuit stub with a metal through hole is placed into the symmetrical resonator together with a pair of step impedance stubs and a pair of uniform open-circuit stubs. Inside the resonator, the open stubs fold in on themselves, minimizing the circuit for integration with other parts and enhancing the selectivity of the filter. Even-odd mode theory can be employed to investigate the circuit because of the resonator geometric symmetry. The first and second operational frequency bands can then be built using the calculated odd and even mode frequencies to match our requirements. The manufactured experimental dual-band filter is compared to the simulation results, and the statistics revealed good agreement. The calculated structural measures 0.13λ_g × 0.1λ_g.

Through wall radar imaging and detection applications are growing significantly. However, the target response is usually accompanied with a strong clutter which veils the target detection. In this paper, a new algorithm is proposed for clutter reduction and target downrange correction in through wall monostatic radar imaging. The proposed algorithm arranges the received radar signals in a matrix and then splits this matrix to frames. The frames are individually processed and filtered in frequency domain, then they are returned to time domain and merged together in a new matrix. The final step is enhancing the target response via a matched filter. The proposed algorithm performance is evaluated by target to clutter ratio (TCR), signal to clutter ratio (SCR), and downrange target position error (DTPE) in three different simulated scenarios. The simulation results exhibit the proposed algorithm capability in both removing the clutter and adjusting the target downrange to be with an evident appearance and accurate position. In the most complicated scenario which consists of two separated walls and a target behind them, using the proposed algorithm improves the performance in terms of TCR, SCR and DTPE by 49.7 dB, 70.7 dB, and, 7.6% respectively.

This paper presents a narrow notch band, flexible, wearable ultra-wideband antenna built on a jeans substrate. Prior to designing the antenna, the dielectric properties of the jeans substrate are experimentally investigated. The effects of antenna shape and substrate loss characteristics on resonant performances are discussed with reference to the notch characteristics. The proposed antenna is shaped like a cumulative rugged element, with two identical legs. The investigation of the designed antenna shows the operating frequency ranges (S₁₁ ≤ -10 dB) in 2.4-4.2 GHz and 5.86-10.7 GHz bands with notch properties in telemetry/mobile communications (4.4-4.99 GHz) and WLAN (5.15-5.85 GHz) band. Additionally, the prototype is investigated under on-body conditions. Measured results are also included for the validation of the designed prototype.

In this manuscript, a miniaturized Multi-Input Multi-Output (MIMO) antenna with dual-notch characteristics is designed for Ultra-Wideband (UWB) indoor positioning system. The proposed UWB MIMO antenna has a compact size of 35*35 mm² with four orthogonally placed antenna elements on the print circuit board (PCB) with FR4. Each radiating element utilizes the combination of a rectangle and an irregular pentagon, and etches two inverted L-shaped slits to generate two notches in WLAN (5.00 GHz-5.82 GHz) and X-band (7.11 GHz-8.20 GHz). On the grounding planes, the rectangle grounding units are modified into L-shaped branches, on which stepped open-circuit slots and right-angled triangle truncations are etched to broaden the impedance bandwidth. Furthermore, three equidistant rectangular decoupling slits are etched to improve the isolation. The measured results are in good agreement with the simulated ones, which shows an impedance bandwidth of 116.68% (2.96-11.25 GHz) with isolation better than 17 dB. The antenna also has excellent characteristics of good radiation characteristics, total active reflection coefficient (TARC), diversity gain (DG>9.99), low envelope correlation coefficient (ECC<0.005) and channel capacity loss (CCL<0.4 bits/sec/Hz), which can be used in portable UWB-MIMO indoor positioning system.

This paper presents a novel reverse salient pole flux controllable permanent magnet (RSP-FCPM) motor topology, and the motor rotor is reasonably designed to have reverse salient pole characteristics and flux controllable characteristics. After selecting the design variables for the RSP-FCPM motor using sensitivity analysis, a multi-objective genetic algorithm is applied for multi-objective optimization. The optimized RSP-FCPM motor is simulated and compared, and the results show that the optimal RSP-FCPM motor has better flux weakening capability, wider speed range, and constant power output area. it can solve the problem of difficult flux changes of the conventional interior permanent magnet motor, and other electromagnetic performances are also more advantageous. To confirm the reliability of the rotor structure during operation, a stress analysis of the rotor is performed, and the results show that the rotor structure can fully withstand high-speed and high-temperature conditions and can operate safely and stably. It also has more advantages in noise performance, which has great prospects for application in the field of electric vehicles.