Marina Y. Koledintseva

Application of generalized Snoek's law over a finite frequency range: A case study

Generalized Snoeks law proposed in an integral form by Acher and coauthors is a useful tool for investigation of high-frequency properties of magnetic materials. This integral law referred to as Achers law allows for evaluating the ultimate performance of RF and microwave devices which employ magnetic materials. It may also be helpful in obtaining useful information on the structure and morphology of the materials. The key factor in practical application of Achers law is an opportunity to employ either measured or calculated data available over a finite frequency range. The paper uses simple calculations to check the applicability of Achers law in cases when the frequency range is limited and the magnetic loss peak is comparatively wide and has a distorted shape. The cases of large magnetic damping, pronounced skin effect, and inhomogeneity of the material are considered. It is shown that in most cases calculation of the integral through fitting of actual magnetic frequency dispersion by the Lorentzia...

Improved Experiment-Based Technique to Characterize Dielectric Properties of Printed Circuit Boards

Recently, an experiment-based traveling-wave technique to separate conductor loss from dielectric loss on printed circuit board (PCB) striplines, called the differential extrapolation roughness measurement (DERM), has been proposed. The further development of this procedure is presented in this paper. The new procedure is applied to both loss constant and phase constant, as opposed to the previous procedure, which is applied to only loss constant. A new roughness parameter QR to quantify conductor surface roughness has been proposed, and it is used in the improved procedure. This allows for more accurate extraction of dielectric constant and loss tangent over a wide frequency range. In this paper, the three sets of test vehicles are studied. Each set has three different types of copper surface roughness profiles; two of these sets are known to have the same dielectric, which is used for the validation of the proposed extraction procedure. The new corrected extracted dielectric parameters as functions of frequency for these sets of test vehicles are compared with those obtained using the previous DERM technique.

Quantification of Conductor Surface Roughness Profiles in Printed Circuit Boards

Conductor (copper) foil surface roughness in printed circuit boards (PCBs) is inevitable due to adhesion with laminate dielectrics. Surface roughness limits data rates and frequency range of application of copper interconnects and affects signal integrity (SI) in high-speed electronic designs. In measurements of dielectric properties of laminate dielectrics using traveling-wave techniques, conductor surface roughness may significantly affect accuracy of measuring dielectric constant (DK) and dissipation factor (DF), especially at frequencies above a few gigahertz, when copper roughness is comparable to skin depth of copper. This paper proposes an algorithm for characterization of copper foil surface roughness. This is done by analyzing the microsection images of copper foils obtained using optical or scanning electron microscopes. The statistics obtained from numerous copper foil roughness profiles allows for introducing a new metric for roughness characterization of PCB interconnects and developing “design curves,” which could be used by SI engineers in their designs.

Comparison of mixed-mode S-parameters in weak and strong coupled differential pairs

In this paper, it is studied how the rate of coupling (weak vs. strong) in edge-coupled differential transmission lines on a printed circuit board (PCB) affects frequency behavior of mixed-mode S-parameters. This is important for signal integrity (SI), and also may be useful from electromagnetic compatibility (EMC) point of view, since the enhancement of mode conversion (from common-mode to differential mode, and vice versa) may result in common-mode noise in high-speed digital electronics. Slightly imbalanced in length microstrip and stripline differential pairs are considered. The study is done using full-wave numerical electromagnetic simulations. Various technological features are modeled in this work: rectangular vs. trapezoid shape of a signal trace cross-section; copper foil roughness; solder mask over microstrip lines; and presence of an epoxy-resin “pocket” (EP) between the stripline traces (dielectric properties of the EP are different from the homogenized parameters of the ambient dielectric where these traces are embedded).

Full-wave simulation of an imbalanced differential microstrip line with conductor surface roughness

This study investigates the full-wave numerical electromagnetic analysis of edge-coupled differential microstrip lines on a printed circuit board (PCB), when conductor surface roughness is taken into account. Mixed mode parameters of such lines are analyzed. The imbalance in the electric lengths of the traces causes the appearance of common-mode currents, as well as mode conversion: differential mode (DM) to common-mode (CM) and CM to DM. The presence of the solder mask on top of the PCB with microstrip traces is also taken into account. The differential lines modeled in this work are of three types: straight, bent, and curved. The signal traces are modeled with rectangular cross-section, as well as with the more realistic trapezoidal. The effect of surface roughness on the mode conversion is studied numerically in this work.

Hybrid polymer composites for electromagnetic absorption in electronic industry

The objective of this chapter is to provide an overview of the use of hybrid polymer composites in the field of electromagnetic compatibility. The principles and theory of electromagnetic shielding are reviewed, and the respective fundamental quantities are defined. With a view to the actual applications, the materials requirements for the noise suppression sheets and electromagnetic wave absorbers are discussed. Thereby, the critical issues of reliable material properties characterization and electromagnetic performance evaluation are considered. Particularly, expressions of reflection bandwidth are developed and proposed as appropriate figures-of-merit for absorbing materials. Finally, by reviewing the studied multicomponent filler systems, the different approaches in composites design to achieve suppression of reflectance or transmittance are presented.