Conformity Magazine - March 2008 - (Page 50)

Figure 2b plots the shielding effectiveness (SE) results using one software tool (CST Microwave Studio®), other numerical techniques as well as measurements. A good agreement can be observed over the considered frequency range 0-1000MHz. The use of 3D EM field solvers provides a visual idea of the field distribution and, therefore, allows the hot-spots of the design to be easily identified. For example, Figure 2c clearly shows how the field distribution remains confined outside the enclosure for the frequency value of 500MHz, but penetrates inside the enclosure thought the aperture located in the front panel of the box when the frequency is increased to 1GHz. This type of consideration, which might seem easy and almost predictable, might be difficult to achieve in reality without the usage of a proper simulation tool. Example of EM Modeling and Simulation Strategy A view of the metallic enclosure analyzed in this section is shown in Figure 3 [8-9]. It is a 370 x 90 x 296 mm box, with 2 rectangular apertures of dimensions 126 x 14 mm and 80 x 60mm in the front panel. On the top of the box a cover is mounted and inside there are two boards and a heat sink. The thickness of the metal walls (PEC) is t = 2 mm, and the dielectric material of the board has relative electric permittivity er = 4.0. The board to be analyzed is a typical 6 layers PCB with hundred of nets, vias and connections. The PWR plane is split in islands by means of gaps. Due the complexity of the board, the dynamic link with a PEEC based code [3] is used to evaluate the current distribution on the PWR plane. The calculated field can be then used within the selected software tool or [6] in order to perform the 3D numerical simulation of the metallic enclosure, according to the workflow design process summarized in Figure 1. Electric field components are calculated in a specific location 3m distant from the front panel of the metallic box, and the SE is also analyzed. In the considered frequency range, the EM fields inside the enclosure are dominated by the first two waveguide modes, and the orientation of the slots located in the front part of the enclosure is such that the Figure 2: Example of model validation by comparing results due to different numerical technique as well as measurements: a) 3D EM model, b) results, c) electric field plot at 500MHz (left side) and 1GHz (right side). Figure 3: View of a typical metallic enclosure (left side) and radiation source detail (right side) 50 Conformity marCh 2008

Table of Contents Feed for the Digital Edition of Conformity Magazine - March 2008

Conformity Magazine - March 2008 NewsBreaks Editor's Note Adelstein Renominated to the FCC Industry Canada Publishes FAQs On RF Fields FDA Gives Its Scientific Capabilities Poor Marks FDA Offers Guidance On its Product Review Process FDA Publishes Updates to List of Recognized Standards FDA Warns of Patient Risk From Electric Dental Handpieces Complying with the EMC Directive, Second Edition ESD Open Forum Emerging Issues in Standards - Korean "RoHS": Not Like RoHS at All The iNARTE Informer Challenges in Testing - Field-Induced Charged Device Model: What Really Happens Design Fundamentals - EMI Shielding Technologies for Consumer Electronics Equipment Focus On...Compliance Software Buyer's Guide Additional Standards Published for the EU's ATEX Directive Additional Standards for the EU's Medical Devices Directive Also Published China to Require Bar Codes to Enhance Product Safety CPSC Releases 2007 Self-Assessment CPSC Actions in News IEC Standards Update UL Standards Update Product Reviews Telcordia Standards Update From Our "You Can't Make This Stuff Up" Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - March 2008

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