Materials with time-varying permittivity are an emerging research area in the electromagnetics and optics communities. From Maxwell's equations, the electric displacement (D) must be continuous in the time domain. However, this requirement is not satisfied for some conventional time domain solvers, which were developed for time-invariant simulations. Here we briefly review several commercial and open-source software packages. Some of them employ a so-called time-static simplification, which works well for time-invariant materials but will fail for time-varying materials. Read more Wending Mai*, Jingwei Xu, Douglas H. Werner

We proposed a new methodology to detect the neurological degenerative diseases in the early stage. These neurological degenerative diseases often occur along with some mark proteins. Instilled by golden nanoparticles, these protein cells can demonstrate optical activity because of their helical structure. In order to detect these mark proteins, we developed a numerical method to simulate the electromagnetic response upon chiral (bi-isotropic) material. The chiral proteins in human head can therefore be detected. The primitive simulation results suggest that the proposed method would be capable of carrying out in vivo detection of neurological degenerative disease using microwaves. Read more Wending…

Stroke is a dangerous disease with a high recurrence rate. Therefore, postoperative patients need timely monitoring of stroke conditions in their rehabilitation stage for early treatment. Recent studies in biomedical imaging have shown that strokes produce variations in the electric permittivity of brain tissues, which can be detected by microwave imaging techniques. Assuming that we have obtained the image of electromagnetic parameters in previous treatment, we can use differential imaging to detect the bleeding points when stroke recurs. However, the computational cost of traditional methods could be prohibitively large, as the bleeding points are small in the early stages of…

Planar periodic structures are widely utilized in microwave applications. The prism-based Discontinuous Galerkin time domain (DGTD) method is optimal to cope with the modeling challenges associated with these planar structures. In this work, we modified the prism based DGTD to take lossy materials into account. A ring-shaped frequency selective surface (FSS) is studied as a representative numerical example. When submerged into water, the operating frequency of the FSS is lowered dramatically. We test the algorithm with distilled and tap water of different conductivity. Results of both examples compare well with references of commercial software, which validates the accuracy of the…

The zeroth-order parallel-plates mode dominates in most parts of the power-ground plates pairs. Domains with such mode distribution can be solved by a simplified 2D algorithm, while only higher-order modes require 3D computation. For DGTD method, different domains can be decoupled with each other by the numerical flux. To distinguish 2D and 3D domains properly, the field distribution has to be known before it is actually solved. This paradox is walked around by a predictive criterion which roughly predicts tn's field distribution based on tn-1's results. Here we introduce an adaptive criterion based on the CFL condition to realize such…

The 2-D/3-D hybrid discontinuous Galerkin time domain (DGTD) method is efficient to deal with power-ground structures that contain elements capable of 2-D simplification. To generalize the capability of the 2-D/3-D DGTD method to deal with various complex structures in engineering design, a criterion is proposed to differentiate 2-D and 3-D elements adaptively. For domain decomposition criterion at time steptn, the electromagnetic field distribution at the previous time steptn-1is analyzed to identify the zeroth-order parallel-plates mode domain. Compared with the classical static distance criterion, this new adaptive criterion makes the approximation error under control, thus enhancing the stability. The 2-D simplification…

Electromagnetic radiation for a printed circuit board (PCB) midplane connector is studied in this paper. By applying integral-equation (IE) based method and characteristic mode (CM) analysis, the current is split into radiating and non-radiating ones. The radiated power from each part of the structure can be quantified using the radiating current. Therefore, the radiation hot spot can be identified for both edge-side coupled and broad-side coupled connectors. Furthermore, the radiation characteristics for these connectors are compared. Read more Ying S. Cao, Xu Wang, Wending Mai, Yansheng Wang, Lijun Jiang, Albert E. Ruehli, Shiquan He, Huapeng Zhao, Jun Hu, Jun Fan,…

An efficient hybrid 3D and 2D discontinuous Garlerkin time-domain (DGTD) methods is proposed for signal/power integrity analysis of multiple arbitrarily shaped anti-pads in power-ground. The entire structure is decomposed into anti-pad-domain (3D) and plate-domain (2D). Complicated fields exist around anti-pad, yet, in plate domain, only zeroth-order parallel-plate mode exists. Therefore, triangular prism element (3D) could be simplified as triangle element (2D), which has fewer unknowns. The accuracy of the hybrid method has been validated by comparison with commercial software. Its flexibility, and enhancement of efficiency, are also demonstrated. Read more Wending Mai, and Jun Hu

A FSS filter with shorting stubs will be designed in this paper. This filter provides compact design and sharp frequency selectivity by using transmission-zeros, and it is designed for a compact E-plane duplexer. It can be fabricated in a simple and economical way. We simulate the filter with CAD tool, and the tested results show good agreement with the design target. Read more Bin Wang, Qingyuan Wang, Ao Liao, Lifeng Chen and Wending Mai