EMC Symposium: Demos, products, and music

2011 IEEE EMC Symposium, August 16-18, Long Beach, CA.

As is typical at the annual IEEE EMC Symposium, attendees had a choice of live demonstrations of EMC concepts, poster sessions of the latest research, technical sessions, tutorials, product exhibits, and more recently, music. On Tuesday, August 16, Bill Kimmel of Kimmel Gerke Associates demonstrated how EMI shielding inside plastic enclosures can still let emissions escape through seams. By placing a 10-MHz oscillator in each of four enclosures, Kimmel used EMI “sniffer” probes and a spectrum analyzer to show how the quality of the EMI shielding around the seams can let emissions out or keep them in.

Later that day, Garth D’Arbreu of ETS-Lindgren explained now reverberation chambers work and their place in EMI testing. “Reverberation chambers work like microwave ovens,” he told his audience. Both enclosures are designed to produce a field, that, on average, is uniform to the object inside. Reverberation chamber use stirring devices to change the field strength while microwave ovens rely on turntables. RF energy, injected into the chamber through an RF antenna pointed into a corner, reflects off the chamber walls, floor, and ceiling. A rotating reflector causes changes in reflection, which produces a changing field strength inside the chamber.

D’Arbreu used a small stirred-mode reverberation chamber to show how rotating the stirring device changes the electric field in the chamber. The video below shows that has the field changes, it illuminates three florescent lamps. The video shows that although not all lamps are on at the same time, they produce light that, on average, is the same.

On August 17, Christopher Semanson, an instructor at the University of Michigan’s Dearborn campus, demonstrated how the location of probes can drastically affect measurements. Semanson used a radiating circuit, excited with a 50-kHz sine wave, to show how oscilloscope probes can form loops that can pick up radiated signals. Two probes, connected to the same signal and ground points but with opposite orientations produces waveforms on the oscilloscope screen that were 180º out of phase. In the photo, Semanson twisted the probe’s ground wire around the probe, which reduced the loop formed by the probe and it’s ground wire. That caused the waveform’s amplitude (gray trace in the photo) to decrease compared to the signal detected by the other probe with a larger loop area (yellow trace). Semanson uses the demonstration to show students that placement of probes matters when making measurements.

Exhibitors on the show floor gave attendees plenty of EMC-related products to see. AR’s application engineering manager Jason Smith was on hand to demonstrate the company’s multistar system, a multitone EMC immunity tester. Consisting of an RF signal generator, and amplifier, and an antenna, the multistar uses software to generate several carriers at once. Smith explained that some EMI immunity tests can tke hours to perform because the test system must scan through a wide frequency range in many steps. The system produces several carriers that all scan at the same time, thus shortening test time. The system software ensures that it won’t simultaneously produce a signal that’s a harmonic of another signal in the scan. That’s because the system scans through frequencies in steps that are based on percentages of the each signal’s starting frequency rather than in fixed-frequency steps.

ETS-Lindgren introduced TILE 5.0 software for automating EMI tests. In TILE 5.0, the company focused on usability by changing the icons to give it a more modern look. TILE 5.0 remains fully backward compatible with files created on previous versions. The company held a user-group meeting at the symposium.

If you’ve ever been inside an anechoic chamber, you’ve probably seen broken absorber cones. To address that problem, ETS-Lindgren introduced the FlexSorb line of absorbers for lining chamber walls. The photo shows that the cones bend without breaking.

Teseq has added DO-160 test automation to its Compliance 5 software package. The software automates EMI emissions and immunity testing. The revision supports versions DO-160 revisions E, F. and G, which include conducted and radiated immunity (Section 20) and emissions (Section 21). The company also introduced the CBA 400M-100 power amplifier, which operates from 10 kHz to 400 MHz at up to 100 W output power. Applications include automotive, aerospace, and military BCI (bulk-current injection) tests.

On Tuesday, August 16, the EMC Society Band made its third appearance at the Symposium. Again led by FDA’s Jeff Silberberg, the band played several familiar tunes and a few of Silberberg’s originals. I played guitar on three songs, accompanying Louis Feudi, who sang “You’ve Got a Friend” and “Can’t You See” I also played an acoustic fingerpick arrangement of “Fields of Gold.’