P. De Langhe

Measurement of low-permittivity materials based on a spectral-domain analysis for the open-ended coaxial probe

A new coaxial probe was designed to measure materials with a low dielectric constant at frequencies up to 1.5 GHz. Inconsistencies found while measuring samples of different thicknesses were solved by abandoning the model of Levine and Papas for the probe and developing a new model. Using the spectral-domain technique, a closed-form expression is obtained for the admittance of a hanged open-ended coaxial line radiating into a planar-stratified material backed by a metal plate. This new expression can be considered as a correction to the model of Levine and Papas. The model considers the dominant mode as well as the effect of higher order modes. With this new model measurements of low dielectric constant materials were performed together with a perturbation analysis of the influence of air gaps. Theory and measurements were found to be in good agreement. >

Design rules for an experimental setup using an open-ended coaxial probe based on theoretical modelling

In order to obtain a number of design rules for a setup involving an open-ended coaxial sensor to measure the dielectric constant of a material, several parameters are investigated. Using the recently developed spectral-domain model a clear view is given of the influence of the thickness of the test sample. Furthermore, a near-field study of the probe shows that reflections can occur at the transverse boundaries if the test sample is very small. The FDTD is used to investigate the minimum sample size required to simulate a medium that is infinite in the transverse direction. Finally, the influence of the flange of the probe is studied in order to determine the dimensions of the flange needed to correctly use the spectral-domain model. >

Near-field scanner for the accurate characterization of electromagnetic fields in the close vicinity of electronic devices and systems

A new in-house developed three-dimensional scanning system for measuring electromagnetic fields close to devices and systems is presented. The scanning system is able to perform translations along a three-dimensional Cartesian grid with arbitrary grid size so that any electromagnetic field component can be measured with high accuracy and detail. A near-field scan of an AT motherboard and of a telecom subsystem is described to illustrate the performance of the scanning system. The measurements show that the scanning, system is an excellent diagnostic tool for the detection of EMC problems in an early stage of product development.

Design and characterization of an active, EMC-dedicated testchip

This paper analyzes the radiated EMC-behaviour of integrated circuits. For this purpose, an active EMC testchip has been designed, focusing on some specific topics such as output driver slew-rate control, on-chip decoupling, ground-bounce reduction, and others. Together with a dedicated EMC-testboard for mounting the chip, as well as a suited EMC measurement set-up, a global configuration is obtained that enables us to perform an in-depth assessment of some important EMC radiating mechanisms at chip level. The first part of this paper describes the design of the EMC-testchip. In the second part, some first EMC-measurements on the testchip are discussed. From this study, it is quantified to what extent output signal staggering and slew-rate control can help in solving EMC-problems at chip-level.

Transfer impedance measurements on the shielding of a multi-pins board-to-board connector

A new triaxial test fixture has been developed for measuring the transfer impedance of the shield of a board-to-board or backplane connector. A lot of attention has been paid to the design of the outer and inner line of the test cell. As a reference, first transfer impedance measurements were done on a commonly used coaxial cable where a good agreement with literature results was found. Various configurations of the connector shield were further measured and compared, showing a large influence of the omission of side and bottom parts of the connector shields.<<ETX>>

Theoretical and experimental quantitative characterization of the near-fields of printed circuit board interconnection structures

In this paper, the near-field radiation from printed circuit boards is studied quantitatively by means of a new in-house developed three-dimensional measurement set-up. Special attention is given to the development, characterization and calibration of the near-field probes. The performance of the whole measurement set-up is evaluated by comparing the calibrated measurements above a single microstrip line with simulated results. A very good agreement is observed. Moreover, by means of a two-dimensional near-field scan over a more complex printed circuit trace, the capabilities of the developed measurement set-up in order to locate and quantify the sources of radiated emission are highlighted.

Accurate theoretical modeling for dielectric measurements with a coaxial slot antenna

A novel coaxial probe has been developed to measure materials with a small dielectric constant (1</spl epsi//sub r/<5) at frequencies in the range of 100 MHz to 3 GHz. Inconsistencies found while measuring samples of different thickness were solved by replacing the model of H.R. Levine and C.H. Papas (1951) for an annular slot antenna by a more accurate model. Using the spectral domain technique, a closed-form expression is obtained for the admittance of a flanged open-ended coaxial line radiating into a planar stratified material backed by a metal plate. The new model can be considered as a correction of the expression of Levine and Papas. The validity of the new model was investigated using the finite-difference time-domain (FDTD) method. Theory and measurements were found to be in good agreement.<<ETX>>

Electromagnetic Calculations using the FDTD-Method for the Analysis of Waveguide Applicators for Microwave Hyperthermia

Electromagnetic calculations for waveguide applicators using the Finite Difference Time Domain (FDTD) method are presented. The algorithm is applied to a water-filled applicator and the computed results are compared to experimental results in a phantom of saline-solution. Influence of the loading on the near field of the applicator is illustrated in the case where a thin plexi-glass plate is inserted between the applicator and the phantom.