This paper presents a novel formulation of the locally-conformal perfectly matched layer (PML) method, called LCPML- log , which uses a logarithmic decay function. The method is designed to solve ...electromagnetic radiation and scattering problems using the 3D vector finite element method (FEM). LCPML- log has two distinct features that distinguish it from previous PML implementations. Firstly, it does not require any parameter adjustments to optimize its performance, making it self-tuning. Secondly, it needs only a single layer, which makes it cost-effective as it reduces the number of unknowns within the PML layer. The proposed method is formulated for the vector FEM based on edge basis functions for 3D scattering problems, and its effectiveness is demonstrated through numerical results.
An adaptive frequency sampling (AFS) strategy is proposed in conjunction with characteristic basis function method (CBFM) to investigate the problem of wide-band scattering from objects buried in ...layered media. Conventionally, the CBFM is implemented to reduce the solution time at a single frequency. However, wide-band analysis of the above problem is still time consuming when a large number of frequency samples (FSs) are employed with uniform sampling. To mitigate this issue and improve efficiency, the AFS algorithm is proposed to select FSs with a reduced number via an iterative process based on error-estimators. The vector fitting (VF) algorithm is used to derive the rational model, which allows to generate the scattered fields in the band efficiently. The key feature of the proposed AFS is it minimizes the number of the FSs and guarantees the convergence of the solution simultaneously. Numerical results demonstrate that the number of required samples is significantly reduced without compromising the accuracy of the solution.
In this paper, we investigate a new printed antenna based on the 2D image of a fractal tree-leaf geometry by studying the effect of the irregular boundary of the proposed antenna on its radiation ...characteristics. Both the impedance matching properties and the radiation patterns of the antenna are studied over the frequency band 1–6 GHz. Four configurations are designed by increasing the complexity of the structure, which ranges from iteration 0 to iteration 3. The fractal properties of the proposed tree-leaf antenna are then compared to those of a conventional fractal antenna with smooth edges. Following this, the proposed antennas are fabricated and characterized experimentally. Finally, results are analyzed and discussed, and a practical application for this new type of antennas is proposed.
Numerical analysis of truncated periodic structures by utilizing conventional method of moments (MoM) technique is challenging because the number of unknowns involved is often very large; hence, the ...computational cost is high. This letter presents a novel approach, based on the dipole moment (DM) method, for analyzing electromagnetic scattering from truncated periodic structures whose geometrical and/or material properties vary locally from those of a strictly doubly infinite periodic structure. The main advantage of using the DM method is that it provides convenient closed-form expressions for the scattered fields, facilitating the matrix computation in the context of the MoM much more efficiently than when the conventional Rao-Wilton-Glisson (RWG) type of basis functions are used for the same computation. Numerical results obtained by using the proposed approach are compared with those derived from a commercial MoM software package, and good agreement is found. The time advantage is clearly evident from this comparison.
An improved three-dimensional circularly polarized quadrifilar helix antenna (QHA) with low profile and wide 3-dB beamwidth is proposed and its performance is investigated both numerically and ...experimentally. The proposed modified QHA is comprised of a short-circuited quadrifilar helical antenna printed on a thin FR4 substrate, with its four ports terminated by 50 Ω resistances. In addition, four monopoles with 90° phase progression are positioned around the quadrifilar helical antenna, and four Archimedean spirals are used to top-load the monopoles. Simulated and measured results show that the proposed antenna achieves a bandwidth of 23.8%, has a 3-dB beamwidth greater than 170°, and its axial ratio is less than three in the entire upper hemisphere over a wide frequency band.
An efficient procedure for the generation of characteristic basis functions (CBFs) over large arbitrary surfaces is presented in this work. The first step is to partition the original object into ...subdomains and then derive the CBFs for these domains by solving for the currents induced by a set of components of the planewave spectrum (PWS). Next, we aggregate the adjacent domains to obtain enlarged CBFs by expanding the original ones in terms of the weighted planewaves used to compute them. This process can be performed iteratively and involves fast, non-expensive matrix manipulation. We obtain a progressive decrease of the number of unknowns, as we increase the domain size, by following the procedure described above.
Multiscale problems in numerical electromagnetics are becoming increasingly common with the advent and widespread usage of compact mobile phones, body area networks, small and nano antennas, sensors, ...high‐speed interconnects, integrated circuits, and complex electronic packaging structures, to name just a few commercial applications. Numerical electromagnetic modeling and simulation of structures with multiscale features are highly challenging due to the fact that electrically small as well as large features are simultaneously present in the model that demands for discretization of the computational domain such that the number of degrees of freedom is very large, thus levying a heavy burden on the computational resources. The multiscale nature of a given problem also exacerbates the challenge of generating very fine meshes that do not introduce instabilities or ill‐conditioned behaviors.
In this paper, we present novel techniques for an efficient solution of multiscale problems in the time‐domain. The proposed techniques handle arbitrarily shaped objects with fine features by using the dipole moment–based method of moments (MoM) type formulation in the MoM domain and electrically large objects in the finite‐difference time‐domain (FDTD) domain. Scattered fields in the MoM domain are obtained in closed forms and directly in the time‐domain at the desired observation points on a planar interface, which are combined with the conventional FDTD update equations. The time‐domain scattered fields computed by using the MoM formulations presented herein are stable in their implementation.
We present a novel Locally-Conformal Perfectly Matched Layer (LCPML) method for mesh truncation in the Finite Element Method (FEM), to solve wave equations derived from Maxwell's equations. The ...original LCPML method was proposed by Ozgun and Kuzuoglu in 2006 16 by utilizing the concept of complex elements in which nodal coordinates of elements are replaced by complex coordinates obtained by using a complex coordinate-transformation. In the proposed LCPML method, named as LCPML-log method, a more efficient coordinate-transformation is used together with new FEM formulation and implementation. The proposed method offers the advantage that only a few (or even a single) PML layer is sufficient to get reliable results. In addition, it does not require any PML parameter tuning, and hence, the decaying wave behavior in PML is achieved self-adaptively. The numerical results of some detailed and systematic performance analyses are also presented.
•A novel Locally-Conformal Perfectly Matched Layer (LCPML) method is presented.•A few PML layers are sufficient for good accuracy without any PML parameter setting.•The proposed method can be applied to arbitrary mesh structure created using conventional mesh generation methods.•The proposed method is validated by comparison with classical PML approaches.•MATLAB codes are provided for the proposed LCPML method.
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