Shifeng Huang

To realize efficient frequency sweep for analysis of periodic arrays, the generalized transition matrix (GTM) method is adopted combining with the cubic Lagrange interpolation scheme in this letter. Utilizing an appropriate reference surface to wrap each module of periodic arrays, the GTM can be constructed to extract the scattering characteristics of the internal scatterer by multiplying three matrices accounting for the inward/outward transferring process and the scattering of the internal structure. In order to achieve efficient and accurate broad band sweep, the cubic Lagrange interpolation scheme is not applied directly to the GTM but separately to its three factor matrices and the field transmission matrices. The synthetic basis functions (SBFs) are established on the reference surface to reduce significantly the computational cost and the number of unknowns. The GTM in the interpolated forms and SBFs can be reused for all modules. Numerical examples show high accuracy and efficiency of the proposed method.

In this paper, novel loop-star basis functions with the multibranch Raw-Wilton-Glisson (MB-RWG) basis functions are applied to obtain the low-frequency stable solution of the time domain electric field integral equation (TD-EFIE). With the help of the MB-RWG basis functions, it is possible to realize the quasi-Helmholtz decomposition in time domain between different regions that are discretized separately with nonconformal meshes, and only need to slightly modify the generation of the loop and star bases at the interfaces. Especially, the temporally differentiated form of the TD-EFIE is tested by the star basis, while the undifferentiated form of the TD-EFIE is tested by the loop basis. By means of the filtering technique, the components of the solution which have the potential of growing exponentially have been treated. Numerical results illustrate the accuracy and robustness of the proposed method in analyzing the transient scattering problems of perfectly electrical conducting (PEC) objects.

A quasi-Helmholtz decomposition with loop-star basis functions including multibranch Rao-Wilton-Glisson (MB-RWG) basis functions is proposed for electromagnetic scattering problems on an object with multiple surfaces. The loop and star basis functions in the interior region of each surface are generated with RWG functions, and those loop functions and star functions at the bordering lines between different surfaces are constructed with MB-RWG and RWG functions. With MB-RWG functions, the proposed loop-star scheme can be applied to two adjacent surfaces with different mesh resolutions directly. Some numerical examples are presented at low frequencies to verify the accuracy of the method.

In this communication, a multibranch Schaubert–Wilton–Glisson (MB-SWG) basis function is proposed for solving volume integral equations (VIEs) involved in electromagnetic scattering problems. MB-SWG is defined on several tetrahedrons in the positive and negative parts that share a common triangular face, replacing two tetrahedrons in the traditional Schaubert–Wilton–Glisson (SWG) basis function. The MB-SWG basis function is convenient for domain decomposition with a coarse mesh scheme in one subdomain and a fine mesh scheme in the neighboring domains. Numerical results confirm the accuracy and versatility of the MB-SWG basis functions applying for dielectric scattering problems.

A multibranch Rao–Wilton–Glisson (MB-RWG) basis function is proposed in this article, which is composed of one positive triangle with a larger edge length and several negative triangles with smaller edge lengths. All negative triangles are aggregated to replace the negative triangle in the traditional RWG basis function, with exactly the same function expression defined on the triangles. The number of negative triangles can be changed in different mesh structures. Similar to traditional RWG basis functions, the proposed MB-RWG basis functions guarantee normal current continuity across the common edges. No line charges exist and the total charge on one MB-RWG is zero. MB-RWG basis functions can be used very conveniently to connect one surface with a coarse mesh scheme to another with a fine mesh scheme and can be flexibly applied in the domain decomposition method (DDM). Numerical results validate the accuracy and demonstrate the versatility of the proposed basis function in modeling multiscale perfect electrically conducting (PEC) objects.

It is required to calculate the stored reactive energy of an antenna in order to evaluate its Q factor. Although it has been investigated for a long time, some issues still need further clarification. The main difficulty involved is that the reactive energy of an antenna tends to become infinitely large when integrating the conventionally defined energy density in the whole space outside a small sphere containing the antenna. The reactive energy is usually made to be bounded by subtracting an additional term associated with the radiation fields. However, there exists no well-accepted accurate definition for this additional term that is valid for all cases. By re-checking the definition of reactive energies, an alternative formulation is proposed in this paper which can separate the reactive energy and the radiation energy explicitly based on source-potentials. The clearly defined reactive energy is bounded without necessity to subtract that additional term, and the resultant formulae are easy to implement.