Moawia Al-Hamid

High-Frequency Electromagnetic Field Coupling to Small Antennae in a Rectangular Resonator

The integral-differential equation for the current of an electrically small antenna inside a resonator, which is induced by given sources, is solved by the so-called “Method of Small Antenna”. The calculated input impedance of the antenna in the resonator and the calculated coefficients of the mutual coupling between two antennas are compared to experimental measurements, performed within the mode-stirred chamber at the University of Magdeburg. For low resonances, when the assumption of electrically small antennas is justified, a good agreement is found.

Influence of parasitic elements on radiated emissions of a boost converter

A highly detailed evaluation of the influence of parasitic elements, e.g. semiconductor inductances and heat sink capacitances, on radio frequency noise of a power electronic circuit is presented, using measurements in time domain. Fast switching semiconductors trigger oscillations during the switching process, that are critical under electromagnetic interference (EMI) considerations. Separate equivalent resonant circuits for the turn-on and turn-off process of a semiconductor in a boost converter topology are derived, representing the most critical oscillation circuits. The discrete semiconductor packages TO220, DPak, and TO247-4 are investigated and compared. The derived results are verified by measurements of the radiated far field in a semi anechoic chamber.

Limitations of a stripline for immunity tests on road vehicle components

The application of the stripline for immunity tests is described in the standard DIN ISO 11452-5. In this paper the electrical characteristics of the stripline and the related limitations were determined. At certain frequencies high field strengths were measured beyond the test volume. This limits the application of a stripline for immunity tests, which causes additional stress to the periphery and the EUT. To lower the field strength in these areas, some approaches were evaluated.

A novel characterization method for cable ferrites using a TEM-waveguide test setup

Cable ferrites are widely used on wires attached to electronic devices and components to fulfill the requirements of the EMC regulations. Until today many manufacturers of those passive components refer to a simple measurement procedure in order to obtain a ferrite-impedance-versus-frequency-chart for their datasheets. This setup renders only a special case for the cable termination which is far away from a realistic application. From the datasheet graph one could conclude that a particular ferrite is less useful above its peak impedance. We want to correct this misinterpretation, as our investigation clearly shows that the attenuation can reach up to several gigahertz. In the following paper we describe a new approach for the characterization of cable ferrites, using a TEM-waveguide. This leads to an equivalent circuit with a new set of more representative ferrite parameters.

The Impact of loading on the occurrence of high order modes in TEM waveguides

The present paper deals with two common test sites, namely the GTEM cell and the Crawford cell. It is shown, what are the fields inside an empty cell and how they change when the cell is loaded with an EUT.