To rapidly simulate the forward electromagnetic scattering of multiple obstacles, we propose a new forward scattering prediction model, which can effectively simulate the propagation of electromagnetic waves in a large-scale environment, accurately calculate the scattering of multi-scale structures, and realize multi-region parallel computation. Specifically, the proposed model consists of an obstacle region and a large-scale environment region. To make the model consistent with the real scene quickly and accurately, the time-domain parabolic equation (TDPE) and the discontinuous Galerkin time-domain (DGTD) method are employed to simulate the propagation of electromagnetic waves and the scattering of obstacles, respectively. At the same time, each region is equivalent to a linear time-invariant (LTI) system, and the transfer function of each system is calculated by the discrete Laplace Z-transform to realize multi-region parallel computation. This model can simulate the propagation of the electromagnetic wave in multiple obstacles more quickly under large-scale background than the existing obstacle forward scattering model. Numerical results demonstrate that the proposed model is effective in terms of accuracy and runtime performance.

In this paper, a novel flexible antenna for the new ISM band is proposed. A multi-objective optimization based on DDEA-SE is performed to optimize the antenna bandwidth and gain. The proposed optimized antenna has a 4 dB maximum realized gain and 50% maximum radiation efficiency on the ISM band. A fractal structure is used in this design to achieve a multi-band antenna. The bandwidth of this antenna covers several 5G bands. This multi-band antenna is fabricated on a cotton substrate. This antenna has a small dimension which makes it suitable for 5G applications. The bending tests are performed, and both simulation and measurement results show the good performance of the proposed antenna.

A compact bandpass filtering antenna operating at 5.1 GHz is introduced. The radiation layer makes up of a U-shaped patch and a trident resonator. The U-shaped patch is both the antenna and the last stage of the filter, which is excited by the insertion coupling part of the trident resonator. To improve the impedance matching and lower stopband suppression, a defective ground structure (DGS) is used. The dimension of the antenna is 0.36λ₀×0.36λ₀×0.01λ₀ (λ₀ is the wavelength at 5.1 GHz) without a complex external feed structure, which has enough bandwidth, a good frequency skirt selectivity, and a flat passband response. The measurement results manifest that the impedance bandwidth is 110 MHz, and the peak gain is 3.88 dBi. In addition, the filtering antenna also has a sharp roll-off rate and a satisfactory level of out-of-band suppression in the stopband.

Exact solutions to Maxwell equations with topological charge based on a modification to Brittingham's single cycle pulses are analyzed demonstrating that they have finite values of energy, momentum and angular momentum. Moreover, the ratio of angular momentum to energy is bounded due to the dependence of the mean frequency on topological charge. We have also analyzed the skyrmionic texture of the electric and magnetic fields showing that it is possible to obtain skyrmionic numbers higher than one for the magnetic field by means of a superposition of pulses with different topological charges and null skyrmionic number.

The limited space of the substation contains a lot of electrical equipment and voltages ranging from hundreds to several thousand volts, resulting in a complex electromagnetic environment in the substation. As the deployment of 5G base stations increases in substations in China, the power-frequency magnetic field in substations will cause problems, resulting in a location problem. This paper develops a circuit model for converter stations, and presents a calculation method that considers the geomagnetic permeability, 3-phase transmission mode, and erection direction influences. The correctness of the calculation method in this paper is verified by comparing the simulation results and calculation results of the substation model. The deployment conditions of 5G base stations in the substation are analyzed according to the national standard of the requirement and measurement methods of electromagnetic compatibility for mobile telecommunications equipment Part 17: 5G base station and ancillary equipment.

⋅A p-adaptive discontinuous Galerkin time-domain method is developed to obtain high-order solutions to electromagnetic scattering problems. A novel feature of the proposed method is the use of divergence error to drive the p-adaptive method. The nature of divergence error is explored, and that it is a direct consequence of the act of discretization is established. Its relation with relative truncation error is formed which enables the use of divergence error as an inexpensive proxy to truncation error. Divergence error is used as an indicator to dynamically identify and assign spatial operators of varying accuracy to substantial regions in the computational domain. This results in a reduced computational cost compared to a comparable discontinuous Galerkin time-domain solution using uniform degree piecewise polynomial bases throughout. Numerical results are presented to show performance of the proposed divergence error based p-adaptive solutions. It is shown that an accuracy similar to that of uniformly higher order solutions is obtained in terms of the scattering width, using fewer degrees of freedom.

A deep learning linear sampling method (DLSM), composed of linear sampling method (LSM) and a convolutional neural network (CNN) of U-Net, is proposed to restore shape of multilayered scatterers with cylindrical or rectangular cross section. Simulations over random samples with different geometrical parameters are used to verify the efficacy of the proposed method.

In this paper, we present an efficient numerical method to calculate the frequency and time responses of the field scattered by an object buried between two random rough surfaces for a 2-D problem. This method is called Generalized PILE (GPILE) method because it extends the PILE method which considers only two surfaces or an object buried under a surface. The GPILE method solves the Maxwell equations rigourously by using a simple matrix formulation. The obtained results have a straightforward physical interpretation and allow us to investigate the influence of the object buried between the two rough surfaces. We distinguish the primary echo of the upper surface, the multiple echoes coming from the lower surface and those arising from the object. The GPILE method is applied to simulate the Ground Penetrating Radar (GPR) signal at nadir. The resulting time response helps the user to detect the presence of the object buried between the two random rough surfaces.

Photonic integrated circuits (PICs) and microwave integrated circuits (MICs) have been widely studied, but both of them face the challenge of miniaturization. On one hand, the construction of photonic elements requires spaces proportional to wavelength, and on the other hand, electromagnetic compatibility issues make it challenging to reach high-density layouts for MICs. In this paper, we review the research advances of miniaturized PICs and MICs based on surface plasmon polaritons (SPPs). By introducing SPPs, miniaturized photonic elements at subwavelength scales are realized on PICs, which can be used for highly integrated interconnects, biosensors, and visible light wireless communications. For MICs, since the metals behave as perfect conductors rather than plasmonic materials at microwave frequencies, plasmonic metamaterials are proposed to support spoof SPPs. Spoof SPPs possess similar characteristics to SPPs and can be used to realize high-density channels on MICs. Moreover, combining the latest theoretical research on SPPs, future tendencies of SPP-based MICs are discussed as well, including further miniaturization, digitization, and systematization.

To improve the performance (low torque ripple, high average torque and high efficiency) of the external rotor switched reluctance motor (ERSRM), a preference multi-objective optimization framework for design and control of an ERSRM based on CD-NSGA-II (Chi-square distance fast non-dominated sorting genetic algorithm) with gradient targets is investigated. Firstly, the structure of the ERSRM is introduced, and the comprehensive sensitive analysis that evaluates the influence of each design variable on optimization objectives is presented. Secondly, the initialization of population, cross-mutation method and sorting method of conventional NSGA-II are improved. Then, the practicability of this method was proved by standard test functions. Finally, the NSGA-II and CD-NSGA2-II are combined with the visual basic script (VBS) script to optimize the ERSRM, respectively. Finite-element analysis results confirmed the validity and superiority of the optimized design.

Benefit from the high resolution, penetrating and all weather advantages of millimeter-wave (MMW) imaging, MMW imaging plays an important role in remote sensing, security inspection, navigation, etc. Among the MMW imaging systems, synthetic aperture imaging radiometer (SAIR) utilizes aperture synthetic technology to achieve higher imaging resolution, but the perception information is insufficient, resulting in poor image quality. In order to improve the image quality of passive SAIR MMW image effectively, we propose a novel multichannel depth convolutional neural network (MDCNN) in this paper. Aiming at the characteristics of original MMW images with more noise in low-frequency information and less features in high-frequency information, wavelet transform is incorporated into the MDCNN to obtain the high and low frequency components firstly. Then, dense residual block and skip connection technology are adopted to denoise and enhance target information in the four independent channels respectively. Finally, high quality MMW images are synthesized by inverse wavelet transform. The simulation results show that the reconstructed images of MDCNN have better image quality (such as image contour and texture details) than other deep learning-based methods.

In order to obtain the analytical expression of the position of sparse array sensors under the condition of a given total array sensor number, a sparse array design method based on direct-connection of 4 uniform linear arrays (DCUA4) is proposed. By using the only known parameter of the total array sensor number, the sensor number and spacing parameters of four subarrays are obtained by mathematical operation, then the four subarrays are directly connected to realize the design of sparse array. It is proved that the aperture of the sparse array is large, and there are no holes. Because all the sensors are allocated to four subarrays, the number of small spacing sensor pairs in the array is controlled The performance of the proposed array is simulated based on the spatial smoothing MUSIC (SS-MUSIC) algorithm. The simulation results show that the proposed DCUA4 can produce a large virtual array aperture, realize high-precision direction of arrival (DOA) estimation under underdetermined conditions, and resist the influence of low mutual coupling.

The growing interest in collision avoidance automotive radar systems in K-band necessitates the development of dedicated antenna systems with 45˚ inclined linear polarization (LP). In this letter, a 45˚ inclined LP array antenna with Taylor distribution is proposed, designed, and fabricated.

Broadband differences interferometeric analysis of a three-layer planar polymer optical waveguide is proposed and optimized to detect the concentration of hemoglobin in blood. The dispersion characteristic and cutoff film thickness of proposed waveguide are obtained by matching the field at various boundaries. The obtained cutoff film thickness for TE₀ and TM₀ modes is 0.09 µm, 0.1 µm at operating wavelength 400 nm, and 0.19 µm and 0.23 µm at operating wavelength 800 nm, respectively. The effective refractive indices of TE₀ and TM₀ modes are obtained at two considered wavelength i.e. 400 nm and 800 nm, and hence the difference of their propagation constant is calculated. It is observed that the propagation constant of these modes decreases with the increase of wavelength. Also, the difference of propagation constant attains its maximum value at certain wavelength and decreases either side of this wavelength. The interference maxima signals at output are considered as sensing signal. The maxima of interference signals, close to the maximum value of propagation constant, are shifted sufficiently with the change in cover refractive index. The maximum sensitivity 3.8 nm/RIU is obtained in the proposed broadband differences interferometeric analysis of waveguide at film thickness 300 nm. Hence, at this film thickness the sensing signal changes by 0.68 nm/g/L of hemoglobin concentration in blood.

This article presents a circularly polarized (CP) dual lens (DL) antenna with high gain and wide axial ratio (AR) bandwidth for automotive radar applications. Proposed antenna system provides low AR and scan loss over a wide angular range. It consists of a linearly polarized (LP), wide band, aperture coupled planar feed antenna, an extended hemispherical lens and a planoconvex lens with thin parallel plates and air slabs. In-lens polarizer mounted to the flat surface of the planoconvex lens converts LP wave to CP state. Fundamental design rules to obtain CP is defined. A CP DL design in low dielectric permittivity material (ε_r=3) is introduced. It achieves simulated efficiency that varies between 75 and 82% within the 77-81 GHz automotive radar band. AR is below 2.2 dB for all scan angles up to 25˚. Realized gain at boresight radiation is 25.6 dBic at the center frequency. 0.85 dB scan loss is observed at ±30˚ scan angle. A frequency-scaled prototype has been fabricated by additive manufacturing process with fused deposition modeling, and the concept is proved by the experimental results in 22-28 GHz band.

In this paper, a rectangular embedded dual band Electromagnetic Band Gap (EBG) structure at frequencies 2.45/5.8 GHz useful in industrial, scientific, and medical (ISM) band for various wearable applications is proposed. The main intent of this work is to design a dual band EBG to reduce specific absorption rate (SAR). The unit cell which is a part of the EBG structure is formed using a rectangular patch. It has a U shaped rectangular slot and a stretched strip with a rectangular patch at end. EBG unit cell simulation is accomplished by solving eigen mode problem in High Frequency Structure Simulator (HFSS). EBG structure has to be suitably designed and fine tuned for specified band stop property to reduce surface waves. It must improve front to back ratio (FBR). With placing antenna on human body, frequency detuning occurs which is undesirable thus emphasizing the need of improvement in impedance bandwidth. This improvement can be achieved by a suitable design of EBG structure. In this work, the proposed EBG structure is integrated with a dual-band monopole antenna at frequencies 2.45/5.8 GHz for wearable application. The evaluation of antenna performance on a four layer body model is carried out. Simulations are used to demonstrate EBG array structure effectiveness for the reduction of Specific Absorption Rate (SAR) on the four layer body model. Computed SAR values for tissue in 1 g and 10 g are within standard prescribed limits. It is concluded that the proposed dual band antenna is appropriate for wearable applications. Proposed EBG array is fabricated and integrated with a twin E-shaped monopole antenna. The measurement of reflection coefficient, radiation pattern, and transmission coefficient of fabricated EBG array is carried out. The measured and simulated results show good agreement. Antenna performance in the event of bending condition and on-body condition is assessed.

With the development of communication technology, people's requirements for information transmission rate are getting higher and higher. Compared with the previous sub 6G frequency band, terahertz communication has a larger bandwidth and a higher rate. This paper studies the influence of azimuth angle of arrival (AoA) and azimuth angle of departure (AoD) on the received signal strength in the 220 GHz-320 GHz frequency band, as well as the influence of the signal passing through different obstacles, different dry humidity and material thickness on the signal power.

A novel metamaterial-based circular patch multi-input multi-output (MIMO) antenna is designed with a `C'-shaped defected ground structure for high isolation. A 4 × 4 mm<sup>2</sup> unit cell for a ring resonator has been designed and exhibited double negative material (DNG) properties from 1.0 to 2.92 GHz and 13.68 to 17.67 GHz and Mu negative material (MNG) from 4.70 to 13.67 GHz. The proposed antenna structure is designed by embedding the ring resonator-based meta-structure to a circular patch antenna and fabricated with dimensions 0.245λ<sub>0</sub>×0.409λ<sub>0</sub> (15×25 mm<sup>2</sup>). The proposed antenna operating at 8.50 to 14.23 GHz for X and lower Ku bands is used in the Unmanned Arial Vehicle (UAV's) applications. The spacing between elements is 0.088λ<sub>0</sub> (5.4 mm) on an FR4 epoxy substrate, and the `C'-shaped structure on the back of the antenna improves the isolation of more than 24 dB in the operating band. Distance between the antenna elements plays a crucial role, and parameters affected by this are optimized by introducing machine learning. For future predictions, a linear regression model was created to optimize the parameters' linear dependencies like isolation and return loss on the distance between the antenna elements. The radiation efficiency and gain of the antenna are enhanced by 92% and 6.02 dB at 13.22 GHz, respectively. The MIMO antenna's simulated results of diversity and other parameters are in the acceptable range with the measured results used for X-band radar applications. The proposed decoupling technique is simple to understand and implement.

In this paper, minimum variance distortionless response (MVDR) algorithm for adaptive Beamforming is applied to a linear array under known mutual coupling among half wavelength dipole (HWD) antennas. This algorithm will minimize the signals from all interference directions while keeping the desired signal undistorted. The problem of calculating mutual coupling coefficient of the array HWD antennas formed into a matrix has been considered. The obtained results show the effectiveness of the proposed method, in which the optimum weighting of adaptive antenna arrays is accomplished by computing the weight vector that achieves maximum towards the desired signal and nulls towards interferers. Also, performance evaluation of this algorithm in terms of complexity, convergence speed, and amplitude response will be present. It is shown from the simulation results that the performance of the beamforming algorithm considering the mutual coupling effect can be improved by the proposed compensation method. We also simulate the signal-to-interference-plus-noise ratio (SINR) with different input signal-to-interference ratio (SIR). The different results obtained are in good agreement with those of the literature.

This article introduces a unique dual-band notched Ultra Wide Band (UWB) Multiple Input Multiple Output (MIMO) antenna. The planned MIMO antenna has two identical Mushroom-shaped radiators with a combined dimension of 18×34×1.6 mm³. Inverted L-structured stubs are joined to the antenna's ground to provide enhanced port isolation. The proposed antenna achieves improved isolation of -23 dB over 3.08-12.8 GHz bandwidth. Two novel strips are extruded in the antenna's ground and mushroom-shaped radiator to introduce a notched WiMAX band (3.37-4.30) and WLAN (5.08-5.80) GHz band. The presented antenna's peak gain is achieved from 2 to 4.8 dBi, and the antenna's radiation efficiency is attained between 78 and 90% except for (3.37-4.30) GHz and (5.08-5.80) GHz stopped bands.