Hermann Singer

On the coupling of an external electromagnetic field to a printed circuit board trace

Compact analytical solutions are developed for the terminal responses of a printed circuit board (PCB) trace exposed to an external electromagnetic field in the frequency and time domain. The analysis based on transmission line theory in a scattered voltage formulation uses a quasi-TEM propagation model for the trace and the exact distribution of the external electric field within the air/dielectric medium for the excitation terms. From the general solutions obtained for arbitrary wave incidence and terminal impedances, several much simpler approximations are derived revealing the principal behavior and indicating the relevant parameters to minimize the coupling. Practical examples with a comparison of the different results are presented.

Numerical Electromagnetic Field Analysis for EMC Problems

Much progress has been made in the use of computational electromagnetics for the analysis of electromagnetic compatibility (EMC) problems during recent years. This paper reviews the improvements in some of the most important techniques of the field: the method of moments, the finite-difference time-domain method, the finite-element method, the transmission-line matrix method, and the partial-element equivalent-circuit method. The results of computer codes on the basis of such methods have to be validated, and some of the respective possibilities are addressed.

State of the art in the method of moments

This article presents new developments in the method of moments (MOM). IT describes some variants of this method which deal with general bodies composed of metallic and dielectric structures. Some procedures are presented which combine the method of moments with analytical methods in order to solve additional problem classes in the area of EMC. Two of these approaches are able to analyse the shielding effectiveness (SE) of electromagnetic shields consisting of nonperfectly conductive materials. Both procedures can be implemented by the method of moments. Two other techniques, which are outlined, are able to treat the induction in lines close to metallic surfaces and to analyse the voltages coupled into cables.

Efficient computation of radiated fields from finite-size printed circuit boards including the effect of dielectric layer

The rigorous analysis of a finite-size printed circuit board by the method of moments based on a full discretization of the whole three-dimensional structure requires a high numerical and modeling effort. A suitable simplification which drastically reduces the computation time is to use an equivalent-wire model for the traces situated within an homogeneous medium with an effective dielectric constant to account for the dielectric layer. For the subsequent determination of the radiated fields the dielectric layer is commonly ignored. In this paper we show in which cases this can lead to considerable prediction errors, and present a method based on polarization currents to include the effect of the dielectric layer, retaining the numerical efficiency of this approach. Examples are given to demonstrate the importance of the proposed extension.

Fast EMC Analysis of Systems Consisting of PCBs and Metallic Antenna Structures by a Hybridization of PEEC and MoM

This paper presents hybridization approaches of the method of moments (MoMs) and the partial-element equivalent-circuit (PEEC) method in order to achieve a significant reduction of numerical complexity. The MoMs is applied as a full-wave method-only where it is necessary-to 3-D metallic scatterers such as antennas. Furthermore, the PEEC method is applied to single-layer printed circuit boards combined with an effective dielectric constant assuming an infinite dielectric in order to avoid discretization of the substrate. In the hybrid approaches of the MoMs and the PEEC method, both techniques are applied consecutively compared to a full-wave MoMs model. The validity of the hybrid approaches and the gain in numerical computation time are demonstrated by three numerical examples, which are related to electromagnetic compatibility. The results are verified by full-wave MoMs reference calculations and by a measurement.

Reduction of Unknowns in PEEC Structures by Exploiting Connectivity of PEEC Cells

The partial element equivalent circuit (PEEC) approach facilitates a combination of electrical circuits and electromagnetic problems because a circuit formulation of that class of problems can be achieved. The majority of the PEEC implementations use circuit solvers like SPICE or ASTAP, allowing a huge degree of freedom in the design of the circuits, which can then be analyzed. However, these solvers have to handle very large equation systems even for small structures, especially if no circuit and network topology information is exploited. In this paper, we present a method exploiting information about the circuit topology, by which we can reduce the size of the PEEC equation system to a minimum. Numerical examples are given and a validation check is accomplished, showing that the approximations that are done in this paper are feasible, and that the numerical results are in good agreement with results that are produced by a method of moments solver.

Application and limits of the MoM-PO-UTD hybridization technique

Hybrid methods have gained in importance for the computation of electromagnetic problems. There are many reasons for this fact. Combining for example the transmission line method with a numerical technique provides the advantage that no line-specific gridding is required. The coupling into cables can be accomplished by computing the forcing terms of the telegrapher equations based on simplified full-wave models. Further examples are the computation or the shielding effectiveness by combining for example the method of moments (MoM) with an analytical solution. In this paper we consider a hybrid technique where the MoM is combined with physical optics (PO) and with the uniform geometric theory of diffraction (UTD). Such an approach involves a number of aspects which are attractive from a practical point of view. Certain rules, however, have to be considered in order to apply and to validate the method successfully in a numerical simulation.

Advanced method of moments based on iterative equation system solvers

The treatment of field and scattering problems by means of method of moments (MoM) produces a system of linear equations which has to be solved. For large-scale structures the numerical effort for an LU decomposition of the system matrix becomes unacceptable. Iterative solvers can be an alternative but they often require a sophisticated preconditioner. A simple but powerful preconditioner can be derived from the physical meaning of the blocks in the impedance matrix and is applicable to a wide range of EMC problems. Using iterative methods can also be of significant advantage in another class of problems.

Use of Huygens source excitation in a MoM surface-current EFIE formulation

In this paper the equivalence theorem (Huygens principle) is applied in conjunction with a method of moments (MoM) surface current formulation in order to improve the computation of a certain class of problems arising in the area of EMC. Of special interest is the effect of holes and slots upon the forming of the interior fields of enclosures. For an effective aperture treatment based on a MoM EFIE formulation the electric MoM currents and the electric equivalent sources (Huygens sources) have to be galvanically connected in order to satisfy the continuity equation at the interface. It is observed that one can circumvent instabilities of the EFIE at resonances leading to false interior fields by replacing the original excitation by Huygens sources in the aperture. In a first standard MoM computation the current distribution of the structure is gained. Then the original excitation is replaced by Huygens currents in the aperture plane. A second MoM computation is necessary to compute the internal current distribution. Such a step-by-step EFIE procedure is computationally more efficient than a double-layer current approach. The numerical effort is reduced by almost a factor of four.

Application of a Hierarchical SVD/ACA Compression Technique to Near-Field Calculations of Monopole Antennas

This paper describes the concept of hierarchical matrices and the application to near-field calculations of voltage or power driven antennas. The hierarchical matrix structure is based upon a binary partition of the structure to be analyzed, where blocks of the matrix can be represented as full matrices or R(k)-matrices, the latter yielding a data reduced representation of the initial block. It has been found that application of only the ACA (adaptive cross-approximation) matrix reduction technique gave bad results in many practical 3D cases and failed to predict the physical current distribution. Way out of this dilemma is to combine ACA with SVD (singular value decomposition), yielding reliable results again. The new compression scheme turns out to be efficient and stable and will be described in detail. By means of examples the validity of the approach is demonstrated, where especially near-field investigations are carried out.