This research extends the theory of binomial array antennas. A closed-form expression for the half-power beamwidth of the array factor of an array antenna is presented. The expression is correct for the ratios of element spacing to wavelength greater than or equal to one quarter. Also, exact equations for determining the half-power beamwidth for main-beam steering are derived. A comparison with an approximate formula for the half-power beamwidth of binomial array antennas is carried out.

In the paper, a wideband circularly polarized (CP) filtering antenna is proposed, which is composed of four bent Vivaldi elements excited with sequential-rotated feeding technique. Since the Vivaldi element has the advantages of high gain and wide bandwidth, it is selected as the radiation element. On this basis, two cross slots are etched on the Vivaldi antenna to increase the gain at lower frequency band, and bent method which has less effect on the overall performance is applied for lowing the profile of the antenna. To realize filtering characteristic, the quadrature four-feed network consisting of one modified miniaturized filtering rat race coupler (FRC) and two compact wideband quadrature couplers is utilized as the sequential-rotated feeding for the Vivaldi elements. Design procedures of the Vivaldi antenna, the modified filtering FRC and the quadrature four-feed network are given. For validation, a prototype is fabricated and measured. Results show that more than 60% fractional bandwidth (FBW) is achieved under the criterions of more than 10 dB return loss and less than 3 dB axial ratio. Within the AR bandwidth, the gain is in the range of 7.5 dBic~10.1 dBic. Out of the operation band, the gain sharply decreases to be lower than -5 dBic with a rectangle coefficient (|Normalized Gain_-10-dB/Gain_0-dB|) of 1.25, which indicates good filtering performance.

A novel miniaturized high-gain Vivaldi antenna printed on a thin substrate is proposed for operation as multi-band antenna for millimeter-wave applications. The present work proposes a novel geometrical design of the Vivaldi antenna that is printed on the opposite faces of a thin dielectric substrate. The antenna has compact size, and its dimensions are optimized to enhance the performance regarding the bandwidth of impedance matching, gain, and radiation efficiency. To maximize the gain within a desired frequency band, each arm of the Vivaldi antenna is loaded by a ring-shaped parasitic element. The results of the parametric study for antenna design optimization regarding the enhancement of the impedance matching bandwidth and the antennas gain are presented and discussed. Also, it is shown through parametric study that the size and location of the parasitic rings can be optimized to enhance the antenna gain over the desired frequency range. The multiband operation of the proposed Vivaldi antenna is explained in view of the multimode operation that is illustrated by the distributions of the surface current on the antenna arms and the electric field in tapered slot. A novel microstrip line/parallel-strip line balun structure is proposed for feeding the balanced Vivaldi antenna and to achieve wideband impedance matching. The proposed Vivaldi antenna is fabricated and subjected to performance evaluation through measurements. It is shown that the antenna impedance is matched to 50 Ω over the four frequency bands: 22.0-27.7 GHz, 32.0-37.5 GHz, 41.5-46.6 GHz, and 51.7-56.7 GHz. The corresponding bandwidths are 5.7, 5.5, 5.1, and 5.0 GHz, respectively with percent bandwidths of 23%, 16%, 11.6%, and 9.2%, respectively. In spite of its compact size, the achieved values of the maximum gain are 6 dBi, 9 dBi, 11.4 dBi, and 12 dBi over the mentioned frequency bands, respectively. Also, the corresponding values of radiation efficiency are 98%, 97%, 95%, and 93%, respectively. The proposed Vivaldi antenna is fabricated and subjected to measurement for experimental investigation of its performance. The measurement shows good agreement with the simulation results.

A novel flexible printed monopole antenna with a windmill-shaped fractal design, which is fed by co-planar waveguide (CPW) is presented in this manuscript for ultra-wideband (UWB) applications. By integrating a modified windmill-shape fractal into the conventional irregular hexagonal-patch, the antenna achieves a significantly wider impedance bandwidth extending up to 156.6% across the frequency band of 1.37-11.25 GHz. Additionally, increasing the number of the windmill-shaped fractals leads to the emergence of further resonances. The overall dimensions of the designed antenna are 50 × 70 × 0.2 mm³, and it boasts an impressive bandwidth-dimension ratio (BDR) of 4457, showcasing exceptional efficiency in utilizing its compact size. The maximum gain reaches 4.8 dBi, while the radiation efficiency attains an impressive 98%. The modified windmill-shape fractal antenna design leverages the multifractal concept, providing monopole antennas with enhanced flexibility in controlling resonances and bandwidth. This manuscript offers a comprehensive presentation and discussion of the process used to improve the impedance bandwidth, shedding light on the antenna's exceptional performance and capabilities.

Circularly polarized gap-coupled designs of corner truncated square microstrip antenna in 2400 MHz frequency spectrum are presented. The gap-coupled design on thinner substrate (~0.036λ_g) yields axial ratio bandwidth of 113 MHz (4.697%) whereas that on thicker substrate (~0.13λ_g) yields axial ratio bandwidth of 471 MHz (19.24%). Both the designs exhibit broadside radiation pattern with a peak gain above 7 dBi, thus satisfying the requirements of WLAN and Bluetooth applications. Simulated results have been experimentally verified, which show close agreement.

In this paper, reactive impedance surface metasurface (RIS-MS) and negative refractive index metasurface (NRI-MS) are used to design a wideband, high gain, circularly polarized slot loaded patch antenna (SLPA) for 5 GHz WI-FI applications. The RIS-MS is utilized to improve the antenna's bandwidth. It is composed of 6×6 metallic circular patches that are periodic. To improve bandwidth, the RIS-MS is placed between the SLPA and ground plane of a conventional antenna. A metasurface lens composed of 6×6 periodic NRI metamaterial unit cells enhances the gain of the antenna. The NRI-MS superstrate is positioned at the optimal height above the conventional antenna. A prototype of the proposed antenna has been fabricated and measured experimentally. The prototype has an impedance bandwidth (IBW) of 21.7% (5.12-6.37 GHz), a 3-dB axial ratio bandwidth (ARBW) of 18.2% (5.19-6.23 GHz), and a gain of 13.5 dBic.

A design of a series-fed antenna array without beam deterioration using miniaturized bandpass filters (BPFs) is proposed. The BPFs are connected behind branches of series feed network (SFN) to compensate the varied phase slope of paths, resulting in constant phase difference between elements across the bandwidth. Hence, the beam deterioration versus frequency is removed. The closed-form equations of the phase slopes for BPFs are deduced, and thus they can be designed quantitatively for phase slope balancing. The proposed SFN has advantages of compactness, simplicity, and low loss. For validation, an 8-element antenna array is designed and measured. The gain and sidelobe level are 12.2-12.39 dBi and 11.67-12.65 dB within the bandwidth of 5.2-5.8 GHz. As comparison, the gain and sidelobe level are 12.85-13.77 dBi and 7.18-12.75 dB using conventional feed network. Therefore, the designed antenna array has stable radiation pattern including beam direction, sidelobe level, and gain.

This paper presents a simple approach for evaluating the complex magnetic permeability of the steel fibers used in concrete according to frequency. The approach utilises the eddy current non-destructive evaluation method, where the electrical impedance is measured using a precision LCR meter and computed using a magneto-harmonic model solved in Py-FEMM software. Initially, the electrical conductivity of the steel fiber is measured using a two-contact DC method. Then, the inverse problem method is applied to identify the complex magnetic permeability. This is achieved by iteratively minimising the difference between the calculated and measured impedances using a simplex optimization algorithm. The proposed approach offers a non-contact, non-destructive, fast, and efficient procedure to evaluate the complex permeability. The obtained results provide valuable insights into evaluating the distribution of steel fibers in concrete.

The research on landslide displacement prediction can help the early warning and prevention of landslide disasters in mining areas. In view of the problem that BP neural network is prone to local convergence, and considering that the network trained based on time-series cumulative displacement may produce large errors in prediction, this paper proposes a method combining displacement increment and CS-BP (Cuckoo Search-Back Propagation) neural network to predict landslide displacement. Compared with the conventional landslide displacement prediction methods, this method uses displacement increment instead of the commonly used cumulative displacement as the network input data, and selects the CS algorithm with few parameters and easy to implement to optimize the BP network to construct the prediction model, and predicts the corresponding amount of displacement change at the next moment by the historical landslide displacement increment. Combined with the measured data of three feature points of a mine in Xinjiang, China, obtained by the micro-deformation monitoring radar, the displacement prediction accuracy of the proposed model on the three measured data sets is compared with the prediction accuracy of the BP, GA-BP (Genetic Algorithm, GA), and FA-BP (Firefly Algorithm, FA) network prediction models based on cumulative displacement and incremental displacement, respectively. The experimental results show that this method achieves superior performance with an average root mean square error of 0.3261 and an average mean absolute error of 0.2785 across the three feature points, outperforming the other models, and holds promising applications in disaster prevention and control work.

This article presents a miniaturized octa-port high gain multiple-input-multiple-output (MIMO) antenna loaded with an electromagnetic band gap (EBG) layer for the use in 5G wireless communication applications. Each resonator of the presented antenna is comprised of a rectangular-like patch with truncated side edges and a partial ground plane. A layer of EBG unit cells is introduced underneath the antenna elements to increase the gain and restrain the surface wave effects, obtaining improved isolation amongst the resonating elements. The -10 dB impedance bandwidth of the prospective antenna with EBG is 12 GHz (21-33 GHz), and it provides isolation of >28 dB. The peak gain of the EBG-backed antenna is 17 dB. The presented mm-wave MIMO antenna offer decent diversity proficiency metrics like envelope correlation coefficient (<0.36), diversity gain (~10 dB), and total active reflection coefficient (-24.75 dB). The overall size of the octa-port MIMO antenna is 27.2 mm × 27.2 mm. The presented MIMO antenna could be used for n257/n258/n261 mm-wave bands.

In standard measurement methods such as NSA 94-106, the low-frequency magnetic shielding effectiveness of a shielding enclosure is tested using the near field of loop antenna. Under this near-field configuration, there is no analytical or closed-form solution for volumetric shielding like box/cavity except for planar shielding like a sheet of infinite extension. Exploring the correlation between volumetric shielding and planar shielding can provide simple prediction methods for volumetric shielding based on planar shielding. As a taste to this end, this article explores the difference between the shielding effectiveness of a double-sheet cavity and a single sheet under the NSA 94-106 standard. We derived the exact solution in integral form for electromagnetic fields inside the cavity and calculated the curves of shielding effectiveness on the frequency with different sheet material, thickness, and sheet-to-sheet distance. The results show that when the distance from the receiving antenna to the back sheet is greater than the diameter of the loop antenna, the results of a double-sheet cavity tend to be consistent with a single-sheet configuration. When the distance is less than the diameter, the difference between the two depends on material type and sheet thickness.

A novel microstrip loop-type resonator with four resonant modes is proposed in this letter. The resonator is formed by a loop-type microstrip line loaded with four shorted stubs. It has a symmetrical structure, thus the odd-even-mode method is adopted to implement the resonant analysis. The novelty of the proposed resonator lies in two aspects. One is that its resonant frequencies can be adjusted in a more flexible way. The other is that its resonant modes have a uniform electromagnetic field distribution, which is beneficial for the excitation of resonant modes. For the purpose of demonstration, based on the novel resonator, a single-band bandpass filter with four transmission poles and a dual-band bandpass filter with two transmission poles in each passband are constructed. Additionally, source-load cross coupling is introduced, and several transmission zeros are generated in the stopband, which improves the out-of-band performance greatly. The designed single-band filter has the central frequency of 2.4 GHz and fractional bandwidth (FBW) of 4.5%, and the dual-band filter has the central frequency of 1.8/2.4 GHz and fractional bandwidth of 2.0%/2.5%. The two bandpass filters are designed, fabricated, and measured. Agreement between the simulated and measured results verifies the effectiveness of the proposed resonator and filters.

Using realistic classical models of microscopic electric-charge electric dipoles and electric-current (Amperian) magnetic dipoles, it is proven that the Einstein-Laub macroscopic electromagnetic force on a macroscopic-continuum volume of these classical dipoles equals the sum of the microscopic electromagnetic forces on the discrete classical dipoles in that volume. The internal (hidden) momentum of the discrete Amperian magnetic dipoles is rigorously derived and properly included in the determination of the macroscopic force from the spatial averaging of the microscopic forces. Consequently, the Abraham/Einstein-Laub rather than the Minkowski macroscopic electromagnetic-field momentum density gives the total microscopic electromagnetic-field momentum in that volume. The kinetic momentum is found for the volume of the macroscopic continuum from Newton's relativistic equation of motion. It is shown that the difference between the kinetic and canonical momenta in a volume of the macroscopic continuum is equal to the sum of the ``hidden electromagnetic momenta'' within the electric-current magnetic dipoles and within hypothetical magnetic-current electric dipoles replacing the electric-charge electric dipoles in the classical macroscopic continuum. To obtain the correct unambiguous value of the force on a volume inside the continuum from the force-momentum expression, it is mandatory that the surface of that volume be hypothetically separated from the rest of the continuum by a thin free-space shell. Two definitive experiments performed in the past with time varying fields and forces are shown to conclusively confirm the Einstein-Laub/Abraham formulation over the Minkowski formulation.

High Frequency Transformer (HFT) acts as the key element of a Solid State Transformer (SST), which is a mandatory equipment in smartgrid system. SST replaces power frequency transformer by providing control and communication in power system. The design of an HFT matching the design of conventional distribution transformer is done in this paper. It is done by developing an iterative algorithm using Brute Force technique. The optimum design is selected by taking minimization of total owning cost as objective function. The algorithm takes eight design variables and four design constraints for shortlisting the optimum design. The optimum design developed is validated in finite element analysis software. The multi-physics analysis of the design is done by interconnecting electromagnetic, mechanical, thermal, and power electronics components of the system. The analytical and numerical analysis follow the same pattern by conducting a case study on the design of HFT with ratings 1000 kVA, 11 kV/415 V, three phases.

A broadband high gain antenna based on metasurface is proposed in this paper. The antenna consists of two layers, the lower layer is a square dielectric plate of 64 mm × 64 mm fed by aperture coupling which brings resonance frequencies closer to each other to improve bandwidth. The upper layer is a substrate of the same size, and the substrate is covered with a metasurface composed of 4×4 triangular slots. The impedance bandwidth is expanded by introducing the metasurface from 6.7% of the single-fed antenna to 23.8%, and the overall height of the antenna is 7 mm. The antenna is excited by an aperture coupled structure consisting of a microstrip line on the back and a narrow slot etched on the ground surface. The impedance bandwidth of the proposed antenna is 23.8%, ranging from 4.8 GHz to 6.1 GHz. The peak gain at 5.6 GHz is about 11.2 dB, and the gain is relatively stable throughout the entire operating frequency band. An antenna prototype is made, and the measurement results verify the design's correctness.

An analytical modeling method for heterojunction bipolar transistor (HBT) is proposed in this paper. The new neuro-space mapping (Neuro-SM) model applied to DC, small signals and large signals simultaneously consists of two mapping networks, which provide the additional degrees of freedom.Sensitivity analysis expressions are derived to accelerate the training process. When the non-linearity of device is high, or the response of the model is complex, the weights in the proposed model are automatically adjusted to address the accuracy limitations. The proposed modeling method is verified by measured HBT examples in DC, smallsignals and largesignals Harmonic Balance (HB) simulation. The modeling experiments of the measured HBT demonstrate that the errors of the proposed Neuro-SM model are less than 2% by matching combined DC, small-signal S-parameters and large-signal HB data, which are less than the errors of the traditional Neuro-SM model and the coarse model. The proposed analytic Neuro-SM model fits the response of the fine model well.

A novel substrate-integrated waveguide (SIW) dual-mode cavity bandpass filter with loaded defected ground structure (DGS) is proposed. The SIW dual-mode cavity operates in two modes, TE₁₁₀ and TE₁₂₀, and the field distribution of the TE₁₁₀ mode is altered by installing a metal perturbation aperture in the middle of the cavity to bring its resonance frequency close to that of the TE₁₂₀ mode, thus forming a bandpass filter with two resonance points in the passband. A DGS structure is embedded at the ground level of the SIW to introduce a transmission zero in the high-frequency rejection band, thus improving the rejection performance of the filter for the high-frequency rejection band. The simulated and measured results show that the center frequency of the filter is 3.75 GHz; the 3 dB bandwidth is 0.3 GHz; the relative bandwidth is 8%; the return loss is less than -15 dB; and the insertion loss in the passband obtained from the simulation is about -0.35 dB, while that obtained from the measurement is 0.4 dB lower than that of the simulation, and the filter has a transmission zero near the high-frequency stopband of 6 GHz, which enables the high-frequency parasitic passband to move away from the passband of the filter. Except for the passband, all other signals in the Sub-6 GHz band can be effectively suppressed by the filter. This design combines the SIW dual-mode cavity with the DGS structure to design the filter, which can realize the flexible adjustment of bandwidth and transmission zero point, and the design method is simple and innovative. The filter can be applied to the 5G n77 frequency band, which has certain application value.

A parameter identification method based on an improved hunter prey algorithm is proposed to address the issues of poor accuracy and speed in traditional permanent magnet synchronous motor parameter identification methods. By using the Fuch infinite folding chaotic strategy to evenly distribute the initial individuals to enrich their diversity and using the golden sine algorithm to optimize the population search path, the algorithm's local development ability and global search ability are improved. The reasons for the dead time effect of the inverter are analyzed, and the input voltage is compensated for through the rotation coordinate method. SIMULINK simulation and physical experiment indicate that the improved algorithm has faster rate of convergence and higher recognition accuracy than the unmodified algorithm, and can effectively identify motor parameters. On this basis, adding dead time compensation effectively eliminates partial harmonics of the phase current and suppresses the occurrence of zero current clamping phenomenon. Compared with the situation without dead time compensation, the identification error of the four parameters has decreased from below 4.23% to below 2.21%.

This paper presents the design of a planar tunable Negative Group Delay (NGD) circuit with low reflections. A pulse-shaped stub inscription on the signal strip of a microstrip line generates a negative group delay, which can then be tuned to a desired value by varying the resistance inside the inscription. Poor reflection characteristics are inherent in such circuits, and a conventional solution like a simple impedance matching circuit compromises the overall NGD performance for a reduced reflection loss. Here, we have included a novel impedance-matching network loaded with absorptive elements at the input/output ports to avoid any reflections from the circuit, while maintaining its NGD behavior and compactness. The measured results validate the proposed design with -5 ns GD at 3 GHz with less than -10 dB reflection loss over the whole NGD bandwidth of 228 MHz at 3 GHz.

The quantum illumination radar uses pairs of entangled photons to enhance the detection sensitivity of a reflecting target. In this paper, we worked on a quantum illumination radar using a pair of entangled photons in polarization in the microwave frequency range in the atmosphere. We studied the quantum information evolution modeling the propagation of a photon in the atmosphere while building two binary decision strategies for the QI radar. We focused on the quantum information evolution showing that the quantum discord representing quantum correlations beyond entanglement could represent an interesting resource to explore for the subject of quantum radar. In addition, we made an approximative estimation of the entanglement survival distance in the atmosphere. Results showed that an optimization should be found to favour the survival of quantum correlations or the signal-to-noise ratios calculated with the binary decision strategy.