S. Criel

Numerical and experimental study of the shielding effectiveness of a metallic enclosure

This paper presents a detailed study of the shielding effectivity properties of metal enclosures. Measurements in anechoic chambers are compared to full-wave electromagnetic simulations. The study is not limited to the frequency range below the first resonance frequency. Different aspects are investigated such as the influence of the size, position and number of apertures, and the effect of the presence of metal plates and of absorbing materials. Where possible, the specific behavior of the shielding effectivity is explained theoretically and existing simple design rules are assessed.

Theoretical and experimental near-field characterization of perforated shields

The shielding performance of an infinitely large, periodically perforated plane shield is investigated, both theoretically and experimentally. Attention is focused upon the near-field characterization by using two loop antennas at both sides of the shield. The electromagnetic coupling between the two loops is analyzed numerically using a plane-wave spectral representation of the radiated field and the method of moments. Comparison of these numerical results with near-field measurements yields a very good agreement up to high frequencies. The predicted classical far-field shielding effectiveness drastically overestimates the near-field shielding performance of the screen. >

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.

Accurate characterization of some radiative EMC phenomena at chip level, using dedicated EMC-testchips

This paper focuses on the radiated EMC-behaviour of ICs and ASICs. An EMC testchip has been developed, encompassing some passive IC interconnection structures. Together with a dedicated EMC-testboard for mounting the IC, as well as a suited EMC measurement set-up, a configuration is obtained that enables one to perform an in-depth evaluation of some important EMC radiating mechanisms at chip level. The EMC-measurements have focused on the comparison between the radiation from IC-interconnects, and the radiation from well-known PCB-interconnects (such as microstrips). From this comparison, the authors observe that an on-chip interconnect may generate significantly more radiation (up to 20 dB for frequencies above 700 MHz) than a microstrip track of comparable length. Especially, packaging effects play a major role in this.

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.

Approximate simulation of the shielding effectiveness of a rectangular enclosure with a grid wall

The shielding effectiveness of a rectangular enclosure, with one wall as a grid, is studied in detail. An approximate technique is used: the holes of the grid are replaced by concentrated magnetic dipoles and the inside of the enclosure is regarded as a piece of a waveguide with only the lowest TE/sub 10/-mode present. This allows the construction of a simple equivalent circuit, from which the shielding effectiveness can be quickly deduced. This simple model has been checked against dedicated experiments, proving its validness even above the first resonance frequency of the empty enclosure.

Comparison of FDTD and MoM for shielding effectiveness modelling of test enclosures

The FDTD (finite difference time domain) method and the MoM (method of moments) are two well known methods for the numerical solution of EMC problems. In this paper, both methods are used to calculate the shielding effectiveness (SE) of a test enclosure with one or two large apertures. For validation purposes, the simple case of an infinite screen with a single rectangular aperture or slot is considered first. The electric and magnetic near field SE is determined for a wide range of slot widths. Very good agreement (less than 2 dB difference between both methods) is obtained for frequencies up to 1 GHz. A larger discrepancy was found for more realistic shielding structures such as the test enclosure, but both methods are still within 5 dB of the experimental results for frequencies below the first resonance of the enclosure.

Near field penetration through a perforated flat screen

A near-field analysis of periodically perforated flat screens is presented. Such an analysis is mandatory in many practical situations, where the source and shield are in each others vicinity. A specific geometry for the analysis of the shielding performance is proposed, based on two current loops (used as excitation and receiving antennas). In this way, a quantitative modeling of the near-field shielding effectiveness can be obtained. Such a geometry links up very well with measurement techniques and existing EMC (electromagnetic compatibility) standards.<<ETX>>

Analysis and modeling of coupled dispersive interconnection lines

A standard method is presented for the analysis and the simulation of coupled dispersive interconnection structures. A high-frequency circuit model which is well-suited for CAD applications is proposed. Considerable attention is paid to the physical interpretation of the full-wave parameters. >

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.