Sami P. Kiminki

Solving IBC-CFIE With Dual Basis Functions

The surface integral equation method is applied to solve electromagnetic scattering by arbitrarily shaped three-dimensional imperfectly conducting objects modeled with the Leontovitch impedance boundary condition (IBC). Dual basis functions are used to remove previously reported difficulties associated with the solution of the combined field integral equation for objects with the IBC. By expanding the magnetic current with quasi-curl conforming dual functions and the electric current with divergence conforming primary (RWG) functions leads to a stable discretization procedure for the rotation (n ×) operator required by the IBC.

SURFACE AND VOLUME INTEGRAL EQUATION METHODS FOR TIME-HARMONIC SOLUTIONS OF MAXWELL'S EQUATIONS (Invited Paper)

During the last two-three decades the importance of computer simulations based on numerical full-wave solutions of Maxwells has continuously increased in electrical engineering. Software products based on integral equation methods have an unquestionable importance in the frequency domain electromagnetic analysis and design of open-region problems. This paper deals with the surface and volume integral equation methods for finding time-harmonic solutions of Maxwells equations. First a review of classical integral equation representations and formulations is given. Thereafter we briefly overview the mathematical background of integral operators and equations and their discretization with the method of moments. The main focus is on advanced techniques that would enable accurate, stable, and scalable solutions on a wide range of material parameters, frequencies and applications. Finally, future perspectives of the integral equation methods for solving Maxwells equations are discussed.

Calderon Preconditioned Surface Integral Equations for Composite Objects With Junctions

A Calderon preconditioned (CP) surface integral equation method is developed for the analysis of scattering by piecewise homogeneous dielectric and composite metallic and dielectric objects. The method is based on the electric current formulation (ECF), which only uses the electric surface currents as unknowns. In the ECF the ill-conditioned electric field integral operator and the well-conditioned magnetic field integral operator appear on separate equations, making the application of the CP much easier than e.g., in the PMCHWT formulation where these operators are mixed. In particular, using ECF, Calderon multiplicative preconditioner (CMP) can be straightforwardly extended for composite objects with junctions. Numerical examples demonstrate that the developed formulation, CMP-ECF, is well-conditioned on a very broad frequency range.

Error-controllable and well-conditioned mom solutions in computational electromagnetics: ultimate surface integral-equation formulation [open problems in cem]

The ultimate goal in computational electromagnetics is to develop numerical methods and algorithms that are effective, stable, and give accurate and error-controllable results over a wide range of frequencies, material parameters, geometries, and applications. This article discusses obstacles and challenges in achieving that goal with frequency-domain surface integral-equation methods.

A Reconfigurable Multi-standard Radio Platform

This paper presents a dynamically reconfigurable multiradio RF architecture concept, which can be used for RF platform and control optimization. The platform realization is based on the RF hardware and its configuration mechanisms. The related control software is realized through functional separation of configuration management and timing control. Both key HW and SW elements are discussed and optimization opportunities evaluated using high level analysis on key building blocks.

Stable Discretization of Combined Source Integral Equation for Scattering by Dielectric Objects

A stable discretization scheme is presented for the combined source integral equation (CSIE) of electromagnetic scattering from three-dimensional arbitrarily shaped homogeneous dielectric objects. The discretization scheme uses both the primary (Rao-Wilton-Glisson, RWG) and the dual (Buffa-Christiansen, BC) functions and avoids numerical problems that would appear if the equations were discretized with the RWG functions only.

Challenges in developing efficient Calderon preconditioners for resonating or high material contrast penetrable objects

Calderon preconditioning is a recently proposed technique for improving conditioning of ill-conditioned matrices arising from discretization of surface integral equations. In electromagnetics the method has been developed for both perfectly conducting and homogeneous penetrable objects. In the case of penetrable objects the large variety of possible material parameters poses additional challenges on the efficiency of the preconditioner. We demonstrate with numerical experiments that problems may appear in particular at high material parameter values, at the physical resonances of the object, and at negative or zero material parameters. As realistic examples of objects with zero or negative material parameters we consider plasmonic nanoparticles at optical wavelengths.

Uniform Surface Integral Equation Formulation for Mixed Impedance Boundary Conditions

A numerical approach based on the surface integral equation (SIE) method is developed for the analysis of time-harmonic electromagnetic scattering by impenetrable objects equipped with mixed impedance boundary conditions (MIBCs). MIBC is an axially anisotropic generalization of the conventional isotropic (Leontovich) impedance boundary condition. The developed SIE formulation utilizes surface Helmholtz decomposition, the self-dual formulation of Yan and Jin, and loop and star RWG functions. A combined field formulation is applied to avoid internal resonances.

Conforming Testing of Electromagnetic Surface-Integral Equations for Penetrable Objects

The necessity of conforming testing procedures in developing accurate and reliable surface-integral-equation-based solvers for homogeneous penetrable objects is demonstrated. It is shown that only in Poggio-Miller-Chang-Harrington-Wu-Tsai (PMCHWT) formulation with a conforming testing procedure, the interface conditions become properly tested for both the tangential and normal field components. Numerical experiments illustrate that the use of a nonconforming testing procedure can lead to a significant decrease on the solution accuracy or erroneous diverging results.

Electromagnetic surface integral equation representations in terms of scalar functions

In this paper surface integral equations are developed for electromagnetics and acoustics. It is demonstrated that in acoustics conventional discretization strategies lead to much better conditioned matrix equations than in electromagnetics. This analysis suggests that in order to obtain better conditioned systems in electromagnetics the surface integral equation representations should written in terms of similar scalar unknowns as in acoustics.