News from the EMC Symposium

The 2005 IEEE EMC Symposium (August 8–12, Chicago, IL) featured more than 200 technical papers presented as open forums, technical sessions, and tutorials. Tutorials covered topics such as Europe's EMC Directive, the fundamentals of EMC design, the fundamentals of signal integrity, and antenna and probe use.

One session featured papers on EMI measurements above 1 GHz. Andrew Marvin presented "Toward Evaluating the Shielding Effectiveness of Enclosures with Contents at Frequencies above 1 GHz." Marvin and co-author Yong Cui experimented with a 480x480x120-mm enclosure that contained a board that radiated EMI. They found that the position of the board inside the enclosure greatly affected the emissions that radiated outside the enclosure. To measure emissions, they rotated the enclosure and scanned across a rectangular area.

Alexander Kriz presented "Validating Anechoic Chambers above 1 GHz Using a Reciprocal Site VSWR Technique." EMI antennas take on different characteristics above 1 GHz, which affects your ability to validate the electromagnetic fields inside a chamber. Kriz showed test results for three test methods, pointing out the advantages and disadvantages of each.

EMC consultant Doug Smith demonstrated how a common ground between two chassis creates interference from one to the other. He used a SPICE simulation to model two equipment chassis placed 1-cm apart and connected to a common ground. With a 1-V, 150-V source, he simulated an excitation on one chassis. Capacitance between the two chassis combined with inductance in the ground wires formed a resonant circuit. At the resonant frequency, the circuit produced a current in the unexcited chassis that was greater than the source current.

In "Shielded Enclosure Accuracy Improvements for MIL-STD-461E Radiated Emissions Measurements," Andy Wang and David Wartenkin explained how they discovered inconsistencies in measurements made in shielded enclosures that complied with the MIL-STD-461E standard. www.emc2005.org.