Research topics

Overview of the main research topics in the Electromagnetics Group

Computational Electromagnetics

The Electromagnetics Group has built a long tradition and world-wide reputation in the area of numerical solutions to electromagnetic field problems. Our research interests include full-wave solving methods, such as the method of moments (MoM), the fast multipole method (FMM), the finite element method (FEM), and the finite-difference time-domain (FDTD) method. Furthermore, there is expertise in stochastic modelling and uncertainty quantification, polynomial chaos, etc. On the one hand, the numerical methods developed by the EM Group are commercialized through links with the industry. On the other hand, practical problems are solved on demand of various Flemish and international companies. Our full-wave algorithms were applied to model practical problems concerning antenna design, radio wave propagation, electromagnetic aware design for the solution of signal integrity and power integrity problems (SI/PI) in electronic circuits and electromagnetic compatible (EMC) design.

The method of moments is one of the most popular full-wave solvers used in research and industrial applications. Computationally, it is less demanding than FDTD and FEM. However, the corresponding dense matrix equations that have to be solved become ill-conditioned in a lot of practically relevant situations. The Electromagnetics Group, being one of the pioneers in the field of MoM, puts a lot of effort to solve this problem. For this reason, an in-house 3D MoM-solver was developed. Our research focuses on the creation of a preconditioner that solves the current ill-conditioning. This research also extends to hybrid MoM-FEM algorithms, for which purpose the in-house solver Hybrid was made.

In order to speed up MoM-computations, the fast multipole method is used, in order to simulate ever larger and more complex electromagnetic field problems. This research builds on a long tradition of the application of integral equations in the EM Group to compute electromagnetic fields. Active research activities deal with the development of fast multipole and fast Fourier transform methods as well as parallellisation of these methods in GRID computing environments. Applications range from waveguide problems, scattering problems,material design, passive optical components to electromagnetic compatibility problems. Research on fast multipole methods and time-domain integral equation techniques is done in close collaboration with Prof. Eric Michielssen from the University of Michigan in Ann Arbor.

Open FMM is a free collection of our electromagnetic software for scattering at very large objects. It currently consists of a fast two-dimensional TM solver Nero2d. In the near future, a full wave solver aimed at simulating photonic crystals will be added. Work on a full wave three-dimensional solver is currently in progress. We aim for solvers that are capable to handle extremely large problems. The Nero2d solver, makes use of a parallel variant of the Multilevel Fast Multipole Algorithm (MLFMA).

The finite-difference time-domain (FDTD) method is one of the prevalent numerical techniques to model electromagnetic wave propagation directly in the time domain. Therefore, it benefits from broadband information after a single run as well as the ability to treat complex media with non-linear behaviour. The FDTD method typically uses a large number of unknowns due to its volume discretisation, which is fortunately balanced by its simple arithmetic and massive parallellisability. Despite its intuitive nature, a lot of research is done to improve the performance and accuracy of FDTD solvers by developing subgridding techniques, hybrid implicit-explicit methods, model order reduction techniques, collocated discretisation, ...

The Electromagnetics Group also has a wide interest in uncertainty quantification, sensitivity analysis and stochastic modelling of S-parameters and other electrical properties of devices. A lot of research has been done on the application of polynomial chaos expansion with the Stochastic Galerkin Method and the Stochastic Collocation Method for the parametric quantification of uncertainty. There is also a growing interest in borrowing elements from machine learning and statistics to model stochastic variability.


Antennas and Propagation: Wearable antenna systems and body-centric communication

Textile wireless node Textile wireless node composed of a dual-diversity transceiver,
dual-polarized antenna, sensor and microcontroller.

The new 5G wireless communication paradigm requires high-performance antenna systems that are unobtrusively and invisibly integrated and that provide stable radiation characteristics in a wide range of adverse conditions. In addition, such antenna topologies must be low-cost and low-profile and conform to the surface on which they are deployed, or they should be flexible.

Since more than a decade, we have been developed dedicated design frameworks for such antenna systems in the context of body-centric communication, the Internet-of-Things and the 5G system. By applying advanced full-wave-circuit co-optimization, an optimal interconnection between the antenna module and the active transceiver and power management electronics is implemented. The direct integration of all sensing, communication and energy-harvesting functionality on the antenna module results in a highly-efficient, compact and reliable design. Moreover, deployed in antenna array configurations, these units may implemented advanced multiple-input multiple-output (MIMO) signal processing algorithms to optimize throughput and/or reliability while minimizing power consumption. All proposed antenna solutions are prototyped and fully tested, both in standardized free-space conditions via measurements in the anechoic chamber, and in real-life deployment conditions.

Electromagnetic Compatibility and Signal/Power Integrity

Bulk current injection test

Bulk current injection test to verify immunity
of integrated circuits.

The group is also very active in the field of Electromagnetic Compatibility and Signal/Power Integrity, mainly in the context of electromagnetic immunity and emission models for integrated circuits (ICs). For example, we model electrically large test benches which are used in the EMC automotive industry, we model both narrow band EMC tests and broadband EMC tests. Examples of this are: capacitive coupled test, inductive coupled test, ESD test, bulk current injection test, direct power injection test,… We also investigate power integrity and signal integrity such as serpentine delay lines, bend discontinuity, power-ground buses, non-uniform multi-conductor transmission lines,… at which we also study the functionality under hazard condition such as radiation immunity.