Opening a new door to tailoring electromagnetic (EM) waves, temporal boundaries have attracted the attention of researchers in recent years, which have led to many intriguing applications. However, the current theoretical approaches are far from enough to handle the complicated temporal systems. In this paper, we develop universal matrix formalism, paired with a unique coordinate transformation technique. The approach can effectively deal with temporally stratified structures with complicated material anisotropy and arbitrary incidence angles. This formulation is applied to various practical systems, enabling the solution of these temporal boundary related problems in a simple and elegant fashion, and also facilitating…

Temporal boundary value problems (TBVPs) provide the foundation for analyzing electromagnetic wave propagation in time-varying media. In this paper, we point out that TBVPs fall into the category of unbounded initial value problems, which have traveling wave solutions. By dividing the entire time frame into several subdomains and applying the d’Alembert formula, the transient expressions for waves propagating through temporal boundaries can be evaluated analytically. Moreover, unlike their spatial analogs, TBVPs are subject to causality. Therefore, the resulting analytical transient solutions resulting from the d’Alembert formula are unique to temporal systems. Read more Wending Mai and Douglas H. Werner

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…