As a noninvasive imaging technique for the interior of objects, Electrical Impedance Tomography (EIT) is widely used in many fields of biomedicine. Sparse reconstruction algorithms have made major breakthroughs in the field of image reconstruction in recent years. The K-SVD algorithm is an adaptive dictionary signal sparse representation algorithm, which could improve the reconstruction accuracy. However, the parameters in the K-SVD algorithm are fixed, which cannot match all the measurement data of EIT very well. Moreover, the K-SVD algorithm adopts a greedy algorithm in the sparse coding stage, which has high computational complexity. In this study, an electrical impedance sparse imaging method based on DK-SVD (deep k-singular value decomposition) was designed. It provides the corresponding optimal model parameters for each set of measurement data through the method of multi-layer perceptron (MLP) network training, thereby improving the imaging quality. At the same time, the iterative soft threshold algorithm (ISTA) is used in the sparse coding stage to improve the convergence speed. The reconstruction results show that compared with the K-SVD algorithm and Total Variation (TV) algorithm, the reconstruction error of the DK-SVD method is smaller, and the irregular and sharp inclusions can be accurately reconstructed. Image artifacts are also greatly reduced.

The design procedure for UWB balun realized in the microstrip technology is proposed in the paper. The procedure applies Artificial Neural Network which corrects the dimensions of the approximate design found by appropriate scaling of the dimensions of the prototype. The scale coefficients for longitudinal and transverse dimensions of microstrip lines are determined from electromagnetic modeling based on transmission line equations. The scaling procedure of radial stubs is also proposed. The design procedure was verified experimentally for exemplary balun with radial stub.

Robust optimization design of brushless electrically excited synchronous machines (BEESMs) is a problem that has received extensive attention. The increase in finite element calculation cost due to the increase in the number of motor parameters is one of the main problems faced by optimization. In this paper, a robust multi-objective optimization design method of BEESM based on an improved hill-climbing algorithm is proposed. All design parameters are divided into three subspaces according to the sensitivity by the sensitivity analysis method combined with Kendall's rank coefficient, thereby reducing the consumption required for FEM calculation. The screening problem of Pareto frontier solutions is solved by an improved hill-climbing algorithm. The candidate points to be optimized are screened through the improved climbing algorithm, and only the candidate points located on the Pareto frontier will be optimized, which ensures the high performance of the candidate points. Based on the noise problems that may occur in actual production and processing, the candidate points are robustly analyzed, and the optimal design is screened out. The robust optimization design method proposed in this paper can reduce the computational cost and improve the robustness of the motor based on improving the performance of the motor.

The design and analysis of a dual-band two-port multiple-input-multiple-output (MIMO) antenna with high isolation suitable for fifth-generation (5G) and wireless local area network (WLAN) applications are introduced in this paper. On the top of the substrate, the proposed antenna element is mainly composed of a defected circular ring with an L-shaped strip, an F-shaped stub, and an L-shaped stub. The bottom of the substrate comprises two rectangular defected ground structures and a neutral line with two Y-shaped stubs. The antenna isolation structure is employed to minimize the coupling between antenna elements, which is larger than 15 dB. The overall dimension of the proposed two-port MIMO antenna is approximately 45 mm × 45 mm × 1.59 mm. The measured -10 dB impedance frequency bands include 3.28-3.72 GHz and 4.44-5.92 GHz, which can cover 5G (3.3-3.6 GHz and 4.8-5 GHz) and IEEE 802.11 a/ac/ax (5.15-5.35 GHz and 5.47-5.85 GHz). The measured efficiency is greater than 60% and 55% at the lower and higher frequency bands. The measured peak gain ranges from 4 dBi to 5.8 dBi in both operating frequency bands. The proposed MIMO antenna is feasible for the 5G and WLAN applications.

In this paper, a compact triangular-shaped multiband Antenna is proposed for linear as well as circular polarization. The proposed Antenna is well-suitable for Wi-Max, C-band, and X-band applications. 2.4 GHz is very well suitable for RFID applications. The antenna is excited with a feed of variable width at one corner of the main patch. The parametric analysis has been done for feed width, slot cutting on the ground, and tapering cut at both remaining corners of the main patch. Circular polarization is achieved due to a tapering cut. It achieved circular polarization at 2.4 and 9.8 GHz and linear polarization at 4.31 and 6.75 GHz. The structure shows an impedance bandwidth of 2.13-3.02 GHz and 4.01-10.00 GHz. The measured peak gain is achieved to be 3.66 dB. A good agreement is found between simulated and experimental results.

A novel quad-band bandpass filter (BPF) consisting of two deformed W-shaped microstrip Stepped-Impedance Resonators (SIRs) with different dimensions is proposed. The W-shaped SIRs are miniaturized from E-shaped SIRs, and each one of the SIRs generates two passbands, and thus four passbands centered at 3.18 GHz, 4.51 GHz, 5.46 GHz, and 8.43 GHz with fractional bandwidth of 6.7%, 9.1%, 8.4%, and 8.2% were obtained. Compared with the basic SIR structures and E-shaped structures, the effective area of the miniaturized SIR is reduced by more than 60% and 20%, respectively. The operating frequency bands can be determined by switching the diodes that are connected to the cross coupling lines of the two SIRs. The improved design can be used for 5G and other applications.

A super wideband antenna is proposed to operate in the frequency band 2.2-22 GHz. The antenna has two planar arms printed on the opposite faces of a three-layer dielectric substrate. Each arm of the antenna is capacitively coupled to a circular ring near its end to increase the impedance matching bandwidth. The dielectric substrate is customized to fit the shape of the antenna arms and the parasitic elements to reduce the dielectric loss. The substrate material is composed of three layers. The upper and lower layers are Rogers RO3003^TM of 0.13 mm thickness, and the middle layer is made of paper of 2.3 dielectric constant and 2.7 mm thickness. The antenna is fed through a wide band impedance matching balun of a novel simple design. A prototype of the proposed antenna is fabricated to validate the simulation results. The experimental measurements are in good agreement with the simulation results, and both of them show that the antenna operates efficiently over the frequency band 2.2-22 GHz with minimum radiation efficiency of 97% and maximum gain of 5.2 dBi. The antenna has a bandwidth to dimension ratio (BDR) of 1755.

The formulation of a matrix-vector product with linear complexity for layer-coupling is discussed in the context of scattering by periodic dielectric scatterers embedded in a layered medium and formulated as a spectral-domain volume integral. It is shown how a traditional formulation in terms of reflection and transmission coefficients can be modified to arrive at an algorithm of linear complexity if used as a matrix-vector product. The computational performance scheme is demonstrated for stacks in which scattering objects are distributed over hundreds of layers.

A planar UHF RFID tag antenna with a hybrid nested slot and T-match network is presented. A novel T-match network in a nested slot is introduced to have superior conjugate impedance matching between tag antenna and the semiconductor microchip. Size curtailment is acquired by means of exploiting the T-match network branches and the feeder strip line. Moreover, expanding the nested slot area and increasing the T-match branch length modify the electrical length and increase the antenna inductance. Thus by utilizing the arm of matching network and feeder, conjugate impedance is achieved in accordance with the semiconductor chip at 865 MHz. A surpassing UHF tag with volume 120×60×1.6 mm³ (0.346λ×0.173λ×0.0046λ), with outstanding 10-dB return loss of 12 MHz has been flourishingly demonstrated, and it is able to obtain a detection range of 13.9 m. This tag antenna composition is simulated with respect to 4 W EIRP reader.

A novel ultrawideband (UWB) antenna with a single parasitic U-type element is reported to exhibit dual-band notch peculiarities. A slotted radiator and a novel defected ground structure (DGS) comprise the proposed antenna, which has a bandwidth of 2.9-11.75 GHz (121%) in the UWB spectrum. By etching a single inverted U-shaped parasitic element on top of the DGS, two rejected bands at the downlink of X-band (6.8-8 GHz) and the uplink of X-band (9.7-11.3 GHz) applications are achieved. The proposed antenna is printed on an FR-4 substrate with a compact size of 24×28 mm², has a gain fluctuation of 1.4-5.7 dBi, and a peak radiation efficiency of 92.3%. The suggested antenna is a viable candidate for downlink and uplink X-band notched UWB applications owing to the excellent agreement between its measured and simulated results.

This paper aims to model and analyze planar antennas for high frequencies using an iterative wave design procedure (WCIP). The formulation adopted in the method allowed determining a basic equation for the interaction of linearly combined electromagnetic fields with the incident and reflected waves in various dielectric media over a discontinuity. In this paper, we design a broadband terahertz patch antenna using graphene. We propose to design a new numerical tool to model the implementation of graphene to achieve an efficient and flexible antenna. The design methodology started with the design of a compact conventional microstrip antenna for 118.87 GHz, and the antenna was then miniaturized using rectangular slots. Based on the simulation results, the suggested structure antenna with a slot can offer great characteristics in terms of broadband performance and frequency reconfiguration using various voltages on the graphene. The antenna provides frequency bands f_r1 = 118.7 GHz, f_r2 = 120 GHz, f_r3 = 123.36 GHz, f_r4 = 128.27 GHz, f_r5 = 131 GHz and f_r6 = 132.8 GHz with a bandwidth is Δf_r1 = 9.5 GHz, Δf_r2 = 3.66 GHz, Δf_r3 = 4 GHz, Δf_r4 = 3.23 GHz, Δf_r5 = 3.401 GHz, Δf_r6 = 3.01 GHz and uniform radiation patterns, the value of VSWR between 1 and 2 for different chemical potential value respectively μ_c = 0.1 eV, μ_c = 0.2 eV, μ_c = 0.3 eV, μ_c = 0.4 eV, μ_c = 0.5 eV, μ_c = 0.6 eV using polyimide with a dielectric constant of 3.5 and a loss tangent of 0.008. In addition, we studied the effect of different substrate materials (Arlon and Duroid 5880). The simulation is performed using a new WCIP equation, and the validation is performed by comparison with the finite integration method in technique (FIT). A comparison of the computation time is presented in this paper.

A dual-band flexible monopole antenna for wearable applications is presented. The antenna structure is built based on Tree-shaped fractal geometry. The suggested antenna is printed on Rogers RT5870, a semi-flexible material with a relative dielectric constant and loss tangent of 2.33 and 0.0012, respectively. According to the results, the proposed antenna achieves dual impedance bandwidth ranging from 1.72 GHz to 1.88 GHz for the lower band and 5.1 GHz to 5.33 GHz for the upper band. The simulated results show that the fractional impedance bandwidths and realized gains of the antenna are 8.9/4.8%, and 1.47/5.67 dBi for the 1.81/5.2 GHz, respectively. The antenna's performance under various bending scenarios has also been demonstrated at both resonant frequencies. The overall size of the proposed antenna is about 45×41×0.25 mm³. The antenna shows good performance to be a candidate for wearable applications.

In this paper, an innovative machine learning (ML) approach for the prediction of the output power generated by photovoltaic (PV) plants is presented. Toward this end, a two-step learning-by-examples (LBE) strategy based on support vector regression (SVR) is proposed to learn the complex relation among the heterogeneous parameters affecting the energy production of the power plant. More specifically, the first step is aimed at down-scaling the weather forecasts from the standard air temperature and the solar irradiance to the local module temperature and the plane-of-array (POA) irradiance. Then, the second step predicts the output power profile given the down-scaled forecasts estimated at the previous step. The advantages and the limitations of the proposed two-step approach have been experimentally analyzed exploiting a set of measurements acquired in a real PV plant. The obtained results are presented and discussed to point out the capabilities of the proposed LBE method to provide robust and reliable power predictions starting from simple weather forecasts.

A design of a modified bow-tie slot loaded wideband antenna using a Substrate Integrated Waveguide (SIW) cavity is proposed in this paper. The simple bow-tie slot perturbs the current distribution of the TE₁₂₀ mode, which generates two hybrid modes, namely odd TE₁₂₀ and even TE₁₂₀ modes at 9.6 GHz and 10.8 GHz respectively, but the achieved bandwidth is only 500 MHz (5.2%). To increase the bandwidth, a short rectangular slot is incorporated at the middle of the bow-tie slot, which moves the hybrid odd TE₁₂₀ mode to 10.2 GHz, near even TE₁₂₀, which helps to achieve a wide bandwidth of 1.1 GHz ranging 9.9 GHz-11 GHz (10.5%), and also it exhibits a unidirectional radiation pattern. The proposed antenna is fabricated for experimental validation of the modified bow-tie slot antenna. The measured value of bandwidth is 1.1 GHz from 10.1 GHz to 11.2 GHz (10.3%) with a consistent gain of 6.25 dBi, and the variation between co-pol and cross-pol is maximal. Because of the wide bandwidth, high gain and compactness, the suggested antenna is suitable for satellite, radar, and all practical wireless applications of X-band frequencies.

A high performance substrate integrated waveguide (SIW) slotted array antenna with low sidelobe level and optimum gain at 28 GHz is designed, and experimental results are presented with simulated data. In order to achieve a low sidelobe level, Chebyshev power coefficients in the form of slot displacements are applied to the SIW array antenna. A MATLAB program has been written to find these slot displacements. This work entails investigating and designing the optimum microstrip to SIW transition over the Ka-Band, designing a 1 x 8 slotted SIW array antenna, and finally applying the Chebyshev power coefficients to the slots of the 1 x 8 SIW array antenna. The fabricated prototype of a 1 x 8 SIW slotted array antenna is tested, and its performance is studied in terms of gain and half power beam width (HPBW), compared with simulations. The measured results of the 1 x 8 slotted SIW array antenna at 28 GHz have a |S₁₁| of better than -20 dB, a gain of 13 dB, and an HPBW of 17˚. The overall dimensions of the design at 28 GHz are 7.143 mm x 51.8 mm x 0.254 mm (0.667λ_o  ×  4.84λ_o ×  0.023λ_o = 0.0766λ_o³ mm³).

This article proposes a compact dual-band circle-shaped implantable antenna for scalp and skin implantation applications. The proposed antenna covers the 1.395-1.432 GHz Wireless Medical Telemetry Service (WMTS) band and 2.4-2.48 GHz Industrial, Scientific, and Medical (ISM) band with a compact volume of 0.0000017λ₀³. The antenna maintains a realized peak gain of -24.5 dB and -20.6 dB, respectively, at 1.43 GHz and 2.44 GHz. Moreover, the gain pattern of the antenna is in the off-body direction which is a desirable feature for implantable scenario. It also depicts stable responses under different implantation scenarios. Moreover, the via free configuration is an advantageous feature of the proposed antenna in the context of fabrication complexity. Furthermore, a holistic design approach is considered with integrated components for device-level architecture. The resonance behavior of the proposed antenna structure is also analyzed by developing a conceptual equivalent circuit model. The evaluated specific absorption rate (SAR) complies with the regulated human safety standard. The biotelemetry link capability is also evaluated through the link margin (LM) calculation of the proposed antenna and is able to establish a communication link at a range of 4.5 m distance.

In this work, the mask-constrained synthesis of domino-tiled phased arrays is addressed. By exploiting tiling theorems and theory, optimal and sub-optimal methods for the synthesis of domino arrangements and the corresponding excitations that minimize the deviation of the radiation pattern from a user-defined power mask are presented. A set of numerical examples, carried out with full-wave simulators and concerned with different aperture sizes and various mask shapes, is reported to assess the effectiveness, limitations, and ranges of computationally-admissible applicability of the proposed methods.

In order to solve the problems of high THD (total harmonic distortion) of air-gap magnetic density, large cogging torque and low power density of permanent magnet (PM) hub motor, a built-in tangential and radial PM combined-pole hub motor is proposed in this paper. The magnetic field provided by tangential PM is the main magnetic field, and the magnetic field provided by radial PM plays an auxiliary role in regulation, which can effectively improve the air-gap magnetic density of the motor, reduce the THD of back electromotive force (EMF), and weaken the peak value of cogging torque. Based on the equivalent magnetic circuit method, this paper analyzes the magnetic circuit of the motor, deduces the leakage magnetic flux coefficient, and reduces the leakage magnetic flux by optimizing the structure of the motor. Finally, the prototype is manufactured and tested to verify the effectiveness of finite element analysis. The results show that the designed PM hub drive motor has low THD of back EMF and good sinusoidality of waveform under no-load condition, and good output performance.

In order to effectively improve filter selectivity and out-of-band rejection level, a multi-cavity two-mode dual-passband filter operating in X-band is proposed. By designing a suitable circuit topology, the bandpasss of the filter are formed using TE₂₀₁ mode in the substrate integrated waveguide (SIW) cavity and the TE₁₀₁ mode in the half mode substrate integrated waveguide (HMSIW) cavity. In addition, incorporating a T-slot structure in the dual-mode SIW cavity can add additional transmission zeros (TZs) and improve the filter selectivity while achieving miniaturization. The center frequencies of the two passbands are 8.67 GHz and 11.52 GHz, respectively. The inter-band isolation is better than 65 dB with three transmission zeros and maximum insertion loss of 0.48 dB and 0.31 dB, respectively. The proposed filter has a compact structure, low insertion loss, high-frequency selectivity, and the measured results agree with the simulated ones.

High torque and power generating capability of double-stator axial flux switched reluctance motor (DSAFSRM) makes it superior to conventional and segmented rotor switched reluctance motors. Despite its significant feature, the ripple in developed torque still limits the usefulness of DSAFSRM for widespread industrial application. This paper proposes anj 8/6/8 pole DSAFSRM with modification in rotor pole shape to reduce torque ripples in respective model. The respective phase windings of the upper and lower stators are excited externally by preparing the circuit in Maxwell software. Each rotor tooth is constructed with two types of slots with different levels of air gap to change the inductance profile. Firstly, the design of a conventional DSAFSRM has been presented; thereafter, some geometric modifications in the rotor tooth have been suggested and investigated to obtain a lower torque ripple at 1200 rpm in proposed DSAFSRM. The efficacy of the proposed motor is investigated through finite element method (FEM) based analysis and also by comparative analysis with other types of switched reluctance motors. It can be inferred from the simulation results that the torque ripple is significantly reduced by 111.16% in the proposed DSAFSRM compared to the conventional DSAFSRM. However, the efficiency of the proposed DSAFSRM (73.87%) is slightly less than the conventional DSAFSRM (74.65%).