GPU communication in multi-GPU parallel FDTD algorithm based on OpenMP and NCCL

The transition to 5G and beyond has highlighted the need for efficient devices that operate at mm-wave frequencies, which require new structures and pose fabrication challenges. This paper proposes a novel non-linear antenna that combines the well-established substrate-integrated cavity (SIC) radiators and time-varying graphene for generating harmonic frequencies in the mm-wave spectrum. Graphene is represented as having a dispersive surface conductivity, while time modulation of the conductivity is introduced by varying the applied bias electric field. A modified FDTD algorithm is, additionally, used to simulate the time-varying graphene behaviour under different modulation schemes. The final antenna design involves an SIC resonator with a graphene-covered slot aperture for radiation. The numerical study highlights the effective generation of harmonics using the modulated graphene at the mm-wave regime. Finally, different modulation schemes are applied to enhance certain higher-order harmonics, demonstrating the potential of this non-linear antenna design for future mm-wave and THz frequency applications.

Efficient Technique for HTS Coupled Resonator Filters Design Using an Enhanced FDTD Algorithm

Analysis and Mitigation of Discretization Errors in the Orthogonalized Integral-Based Subgridding FDTD Algorithm

FDTD algorithm for subcell model with cells containing layers of graphene thin sheets

Abstract Affected by the seasonal freezing area climate, the shallow engineering geological electromagnetic environment exhibits seasonal variations, affecting the propagation process of electromagnetic waves in shallow geological soil. This brings excellent difficulties in accurately identifying the detection target. In this paper, Kaba-he, the seasonal freezing area of Xinjiang, is taken as an example to build a model of the dielectric constant of the temperature variable soil medium in different seasons, and utilizing the high-order O(2,4) FDTD algorithm implemented with MATLAB software. This experiment provides the propagation velocity of electromagnetic waves in shallow subgrade soil of Kaba-he during different seasons and, based on numerical simulation results, gives the calculated depth of the underground targets buried in other seasons. This research can provide theoretical guidance for the application of GPR in Kaba-he.

The finite-difference time-domain (FDTD) method is used effectively to solve electromagnetic (EM) scattering and radiation problems using a 3D sub-gridding algorithm. For accuracy and stability of the FDTD method, the computational domain of EM problems with locally fine structures or electrically small objects is discretized with finer grids. This sub-gridding algorithm for different regions of the computational domain was implemented to increase the accuracy and reduce the computational time and memory requirements compared to those of the traditional FDTD method. In the sub-gridding algorithm, the FDTD computational domain is divided into separate regions: coarse grid and fine grid regions. Since the cell sizes and time steps are different in the coarse and fine grid regions, interpolations in both time and space are used to evaluate the electric and magnetic fields on the boundaries between different regions. The accuracy of the developed 3D sub-gridding algorithm has been verified for radiation and scattering problems, including multiple fine grid regions. Excellent performance is obtained even for higher and different contrast ratios in fine grid regions. Keywords -Finite-difference time-domain method, Sub-gridding algorithm, Temporal and spatial interpolations. Citation -Fatih Kaburcuk and Atef Z. Elsherbeni, "Sub-gridding FDTD algorithm for 3d numerical analysis of EM scattering and radiation problems,"

The overall circuit model and Complex electromagnetic environment model of a typical UAV are built to explore the survivability of multirotor in the complex electromagnetic environment. The composite theoretical calculation model of the metal cavity aperture coupling and internal circuit coupling is constructed using the established UAV circuit model, which is based on the equivalent magnetic dipole algorithm and the FDTD algorithm. The terminal coupling voltage in the UAV circuit and the electromagnetic field distribution inside the metal cavity are estimated. CST software is used to simulate the response of UAV circuits in the same condition, and the correctness of the theoretical calculation model is confirmed. Then, the terminal coupling voltage of the PCB is used to create an electromagnetic coupling efficiency model. The findings reveal that the constructed composite theoretical model can accurately characterize the electromagnetic coupling characteristics of UAV circuits in the complex electromagnetic environment, with an error range of 1%~8%. When comparing the terminal coupling voltage of PCB in various complicated electromagnetic environments, the High-power microwave (HPM) has the maximum coupling efficiency. HPM initially causes the UAV circuits to attain the damage threshold under identical event conditions and target specifications. The findings could be used as a guide for multirotor circuit board protection in the complex electromagnetic environment, as well as for the development of high-power electromagnetic pulse weaponry.

<sec>In spite of the success of fluorescence microscopes (such as stimulated emission depletion microscopy, stochastic optical reconstruction microscopy and photoactivated localization microscopy) in biomedical field, which have realized nanometer scale imaging resolution and promoted the great development of bio-medicine, the super-resolution imaging method for non-fluorescent sample is still scarce, and the resolution still has a big gap to nanometer scale. Among existing methods, structured illumination microscopy, PSF engineering, super-oscillatory lens and microsphere assisted nanoscopy are more mature and widely used. However, limited by the theory itself or engineering practice, the resolutions of these methods are hard to exceed 50 nm, which limits their applications in many fields. Enlightened by synthetic aperture technique, researchers have proposed spatial frequency shift super-resolution microscopy through shifting and combining the spatial frequency spectrum of imaging target, which is a promising super-resolution imaging scheme, for its resolution limit can be broken through continually. Currently, owing to the limitation of the refractive index of optical material, the wavelength of illumination evanescent wave is hard to shorten when this wave is generated at prism surface via total internal reflection, which determines the highest resolution of this spatial frequency shift super-resolution imaging system. Another deficiency of this scheme is the difference in imaging resolution among different directions, for the image has the highest resolution only in the direction along the wave vector of illumination evanescent wave; while, the image has the lowest resolution in the direction perpendicular to the wave vector, which is the same as that obtained by far-field illumination.</sec><sec>In order to solve the above thorny questions, a new model of generating the evanescent wave is proposed, which can generates an omnidirectional evanescent wave with arbitrary wavelength based on the phase modulation of nano-structure, and solve the both problem in imaging system at the same time. To verify the our scheme, we set up a complete simulation model for spatial frequency shift imaging scheme, which includes three parts: the generation of evanescent wave and the interaction of the evanescent wave with the nano-structures at imaging target, which can be simulated with FDTD algorithm; the propagation of light field from near-field to far-field region, from the sample surface to the focal plane of objective lens, which can be calculated with angular spectrum theory; the propagation of light field from the focal place to the image plane, which can be worked out with Chirp-Z transform.</sec><sec>Firstly, with this complete simulation model, we compare the resolution of microscopy illuminated by evanescent wave with that by propagating wave. The experimental results verify the super-resolution imaging ability of evanescent wave illumination and the influence of prism refractive index. The higher the refractive index, the shorter the wavelength of evanescent wave is and the higher the resolution of spatial frequency shift imaging system. Secondly, we demonstrate the resolution difference in a series of directions with a three-bar imaging target rotated to different directions. The result shows that the highest imaging resolution occurs in the direction of illumination evanescent wave vector, and the lowest resolution appears in the direction perpendicular to the wave vector. Finally, we simulate the evanescent wave generated by nano-strcuture and demonstrate its properties of wavelength and vector direction. When applied to near-field illumination super-resolution imaging, the omnidirectional evanescent wave solves the both problems in the model of total internal reflection from the prism surface.</sec><sec>Therefore, the advantages of our scheme are higher imaging resolution and faster imaging speed, no need for multi-direction and multiple imaging, and also image post-processing. In this study, a new spatial frequency shift super-resolution imaging method is proposed, which lays a theoretical foundation for its applications.</sec>

A novel accurate computation method based on the FDTD algorithm for transient analysis applied to hybrid copper-carbon nanotube interconnects

The paper presents a numerical electromagnetic simulations of SAR limited to human tissues based on FDTD algorithm using Sim4Life platform. Flat-bottomed dielectric vessel (flat phantom) and half-wave symmetric dipole antenna were modeled. Simulations were done for the frequencies 0.9 GHz and 0.6 GHz. The analysis were performed according to the IEEE/IEC62704-1 standard and include distributions of electric and magnetic fields around the phantom and antenna. Finally, SAR distributions in the phantom and near the antenna.

Second-order symplectic PRK scheme for ground-penetrating radar simulations in dispersive materials

The use of fractional derivatives and integrals has been steadily increasing thanks to their ability to capture effects and describe several natural phenomena in a better and systematic manner. Considering that the study of fractional calculus theory opens the mind to new branches of thought, in this paper, we illustrate that such concepts can be successfully implemented in electromagnetic theory, leading to the generalizations of the Maxwell’s equations. We give a brief review of the fractional vector calculus including the generalization of fractional gradient, divergence, curl, and Laplacian operators, as well as the Green, Stokes, Gauss, and Helmholtz theorems. Then, we review the physical and mathematical aspects of dielectric relaxation processes exhibiting non-exponential decay in time, focusing the attention on the time-harmonic relative permittivity function based on a general fractional polynomial series approximation. The different topics pertaining to the incorporation of the power-law dielectric response in the FDTD algorithm are explained, too. In particular, we discuss in detail a home-made fractional calculus-based FDTD scheme, also considering key issues concerning the bounding of the computational domain and the numerical stability. Finally, some examples involving different dispersive dielectrics are presented with the aim to demonstrate the usefulness and reliability of the developed FDTD scheme.

ABSTRACT A novel method has been proposed in this paper, which is going to combine the reflection, transmission, and diffraction of electromagnetic waves as one phenomenon – medium effect. Based on medium effect, medium separation method is proposed as a strengthened algorithm for the ray-tracing/FDTD method and as a key to invisibility theory. For the medium effect, obstacles will be considered as controlled sources, and final results are obtained by calculating those controlled sources. Medium separation method will be used as a new interface for hybrid ray-tracing/FDTD algorithm and as a key compensated soft source to realize the theory of perfect invisibility. It can inject any electromagnetic wave into scatterers directly without TF/SF boundary; hence, it is easy to realize the simulation of part of scatterers with finite size, which is illuminated by electromagnetic waves. The medium effect and the method of medium separation are introduced in detail in this paper. Simulation results obtained by medium separation method are in good agreement with the calculation results by traditional FDTD algorithm.

ABSTRACT A novel image reconstruction approach to terahertz pulsed imaging for detecting malignant and fibrous cells within healthy tissue is presented. The non-ionizing effect of the terahertz radiation on healthy tissue makes it a future diagnosis method in medical imaging. The implemented method is based on the convolutional time-reversed FDTD algorithm in the terahertz range. It is computationally efficient and accurately reconstructs images of malignancies from reflected terahertz signals. Besides, the technique is capable of differentiating malignant, fibrous, and fatty cells through the variations of their electrical properties at the terahertz frequency range and well reconstructing their images in 3D. The images created in this method are in high resolution, even for cell-sized malignancies. Furthermore, the proposed technique is compared with conventional terahertz imaging methods and found to have more sophisticated outcomes.

Hybrid FDTD algorithm for electromagnetic analysis of fine structures

ABSTRACT This paper presents an algorithm for predicting crosstalk in multiconductor transmission lines (MTL). Currently, crosstalk has an increasing impact on signal integrity. In the twisted pair cable (TPC), different rotation degrees correspond to different RLCG parameter matrices, these matrices are predicted by the beetle antennae search-back propagation neural network (BAS-BPNN) algorithm, and use implicit wendroff-finite difference time domain (IWFDTD) method to solve near-end and far-end crosstalk voltages. The CST simulation results show that near end and far end crosstalk can be predicted effectively. This proposed method is expected widely used in electronic applications for fast data transfer.

In this paper, we propose and demonstrate an all-fiber high-efficiency focused vortex beam generator. The generator is fabricated by integrating a kinoform spiral zone plate (KSZP) on the top of the composite fiber structure using fs-laser two-photon polymerization 3D nanoprinting. The KSZP with spiral continuous-surface relief feature is designed by superimposing a spiral phase into a kinoform lens, which can efficiently concentrate and transform an all incident beam to a single-focus vortex beam, without the undesired zero-order diffracted light and extra high-order focus. Under arbitrary polarized light incident conditions, experiment results show that the focusing efficiency and vortex purity of the all-fiber generators are over 60% and 86%, respectively, which is much higher than that of a traditional binary SZP integrated on an optical fiber facet. In addition, characteristics of the generated vortex beam, such as focal spot, focal length and vortex topological charge are numerically designed and experimentally investigated. The experimental results agree well with the numerical simulation model using the FDTD algorithm. Due to the compact size, flexible design, polarization insensitivity, high focusing efficiency and high vortex purity, the proposed all-fiber photonic devices have promising potential in optical communication, particle manipulation and quantum computation applications.

Based upon the approximate Crank–Nicolson (CN) finite-difference time-domain method implementation, the unconditionally stable algorithm is proposed to investigate the wave propagation and transmission through extremely thin graphene layers. More precisely, by incorporating the CN Douglas–Gunn algorithm, the piecewise linear recursive convolution method and the auxiliary differential equation method, the analytical model is proposed for Drude-like graphene model. To obtain the solution of the governing equations, the perfectly matched layer and the periodic boundary condition are applied to the graphene structure with two dimensional nano-materials. Numerical examples are carried out for further investigation. During the simulation, the influences of the parameters such as the grating slit and its thickness on the wave transmission are investigated and discussed. The result shows that not only the graphene grating has high transmission performance but also the proposed methods have considerable performance and accuracy.

The standard Yee FDTD algorithm is widely used in computational electromagnetics because of its simplicity and divergence free nature. A generalization of this classical scheme to 3D unstructured co-volume meshes is adopted, based on the use of a Delaunay primal mesh and its high quality Voronoi dual. This circumvents the problem of accuracy losses, which are normally associated with the use of a staircased representation of curved material interfaces in the standard Yee scheme. The procedure has been successfully employed for modelling problems involving both isotropic and anisotropic lossy materials. Here, we consider the novel extension of this approach to allow for the challenging modelling of chiral materials, where the material parameters are frequency dependent. To adequately model the dispersive behaviour, the Z-transform is employed, using second order Padé approximations to maintain the accuracy of the basic scheme. To validate the implementation, the numerical results produced are compared with available analytical solutions. The stability of the chiral algorithm is also studied.