Franz Schlagenhaufer

Near Field - Far Field Conversion Based on Genetic Algorithm for Predicting Radiation from PCBs

A Near Field-Far Field conversion based on Genetic Algorithm has been performed for a printed circuit board with a ground plane. A robust procedure for a pre-selection of dipole moments has been introduced. Important aspects of setting up the conversion problem such as number of equivalent dipoles and choice of matching points have been addressed.

Investigation of near field data sampling approaches for far field radiation prediction of PCBs by genetic algorithm

Near field data sampling techniques, including where to place observation points and how to pre-process the data, are investigated in respect to a Near Field-Far Field transformation. For a simple PCB, the optimum equivalent set of basic radiators is found through a Genetic Algorithm. The magnetic near field amplitudes for different observation surfaces of the PCB are obtained from Method of Moment simulations, and the far field patterns for different frequencies are predicted.

Influence of planar sampling techniques of near field magnitude-only data on predicting far field radiation of PCBs by Genetic Algorithms

Near field data planar sampling techniques, including plane coverage angle, data type and number of observation points, are investigated with respect to a Near Field-Far Field conversion. For a PCB with a loop above a finite ground plane, an equivalent set of dipoles are searched by Genetic Algorithms to approximate the near field data, and then predict the far field. Magnetic near field peak magnitudes are obtained by a Method-of-Moments simulation, and far field prediction is compared with simulated data.

Far-Field Approximation of Electrically Moderate-Sized Structures by Infinitesimal Electric and Magnetic Dipoles

The far field (FF) of electrically moderate-sized structures can be reconstructed by a small number of infinitesimal electric and magnetic dipoles. As an example, the field of a current loop with a perimeter up to 1.5 ¿ is approximated with two dipoles, the parameters of which are found analytically and using a genetic algorithm, respectively. The radiation of a rectangular power-ground plane pair is approximated by dipoles for various frequencies. The minimum number of dipoles needed for a good reconstruction depends on the complexity of the FF, and thus, on the electrical size, in terms of wavelength, of the structure. An estimate for the number of dipoles is given in the conclusion.

Improvements of Robustness of Genetic Algorithm for Near Field - Far Field Radiation Conversion

The robustness of genetic algorithm in finding equivalent ideal electric and magnetic dipoles for near field-far field radiation conversion is improved. The process of selection, crossover and mutation is investigated in detail for solving the sticking problem, and the performance of genetic algorithm is evaluated.

The impact of transmission line terminations on radiated emissions

Terminating transmission lines at either the source or the load side with a damping resistor is often used to improve the signal integrity of clock or control lines on PCBs. While a number of termination variants may produce similar results in respect to signal integrity the EMC performance can differ due to a different current and voltage distribution along the line. This paper investigates the impact of transmission line terminations on radiated emissions.

Figures of Merit for a Hybrid TEM-Reverberation Chamber

A hybrid TEM-reverberation chamber would allow efficient radiated field immunity tests to be performed from DC to microwave frequencies in a single facility. TEM cells are limited to testing comparatively small equipment at relatively low frequencies. Reverberation chambers must be very large to be effective at low frequencies, because the statistical properties of the randomly polarised field break down when insufficient mode stirring occurs [1]. Since there is no frequency overlap between TEM and reverberation operation for a chamber of any given size, a combined TEM/reverberation facility must also operate in a transition mode in order to cover the entire frequency band. This paper proposes performance parameters for overmoded TEM and undermoded reverberation frequency ranges, and gives an example of how the figures of merit can be used to evaluate potential hybrid cell designs.

Shielding performance of a metallic enclosure with slots - numerical modelling and measurements

The shielding performance of a rectangular metallic enclosure with two slots is analysed using a fullwave electromagnetic simulation software based on the method of moments. Measurements are conducted in a 3m semi-anechoic chamber to validate the results. A good agreement between the results gives confidence in the simulation. Thus. simulation tools can be used to predict and optimise the shielding performance of metallic enclosures.

Using N-port models for the analysis of radiating structures

Radiating structures with distributed parameters, such as PCBs, are considered as linear N-port networks and correlations between port currents and field strength values at arbitrary observation points are calculated. Knowing the S-parameters for all accessible ports the port currents can be re-calculated for other source and load scenarios. Field strength values are then obtained as a linear combination of contributions due to the individual port currents. The effect of changing load and source parameters, e.g. varying de-coupling impedances on a PCB, or changing the internal impedance of sources, on radiated fields can then be investigated in a very efficient way without repeating full wavefield simulations.

Rational approximation of transfer functions for radiating structures

The interpolation of transfer functions in the spectral domain is an important issue in the EMC simulation of complex systems. Rational functions provide a good approximation for a wide range of results such as input impedance, induced voltages or field strength values when investigating radiating structures. The estimation whether an approximation is accurate and where to place additional sample frequencies, if required, is given special emphasis.