EMC Symposium now includes signal and power integrity

The 2015 IEEE Symposium on Electromagnetic Compatibility and Signal Integrity, held recently in Santa Clara, CA, kicked off with a keynote address by Dr. Tom Lee, professor of electrical engineering at Stanford University, about the vulnerability of our increasingly complex electrical and communications infrastructure. A major coronal mass ejection (CME) in 1859—the Carrington event—literally shocked telegraphers, although at the time, no one understood the implications. In 1962, the Van Allen belt’s partial CME protection was challenged when the United States detonated a 1.4-Megaton bomb 250 miles above the Pacific near Hawaii to see if the belt position could be shifted. It was, but the resulting EMP also fried microwave communications links, traffic lights, garage door openers, about a third of low-earth-orbit satellites, and Telstar.

According to Lee, the world’s strategy for dealing with CMEs is to be lucky. Of course, a real strategy is needed although very little has been done to harden the current infrastructure, and the next peak CME year is 2022.

Themes

About 100 technical papers were presented on topics such as numerical modeling and simulation, automotive EMC measurements, high-speed link design, and EMC measurements and calibration. A few themes were apparent among the papers I attended.

Large UUT Immunity
To ensure correct operation of the electronic systems that are critical to large EUTs such as cars, aircraft, and ships, high field strengths are specified for immunity testing. Especially at relatively low frequencies, tests are conducted in the near field so that the required field strength can be developed with available amplifiers. AR RF/Microwave Instrumentation is developing very high power amplifiers up to 50,000 W, which are needed to test some military equipment and large aircraft and construction machinery.

A technical paper described how U.S. Army helicopters were tested for susceptibility in the near field at VHF frequencies. To better correlate near-field and far-field effects, the E-field levels and resonances within a 25-ft long slotted cylinder were measured in an anechoic chamber. The results showed that near-field testing reduces internal field levels, creating an under-test condition.

In another example, the FEKO software application was used to simulate the EMC behavior of aircraft made with carbon-fiber reinforced composite materials. Sufficiently high power RF penetrated the fuselage that internal cables required shielding. In contrast, RF energy enters a metal airplane through the windows.

Broadband interference
With many broadband protocols in use, the traditional CW with 1-kHz AM immunity test signal is no longer representative, and instead researchers have proposed using white Gaussian noise (WGN), possibly pulsed and band-limited. WGN also was used to investigate the propagation of broadband signals in reverberant below-deck areas in ships. Measurements and theory confirmed an almost constant average power and E-field throughout the volume. This result depends on having a large number of reverberant modes interacting with a wide range of frequencies in the broadband signal.

Signal Integrity
Both signal integrity and power integrity were included as specific topics within the symposium’s technical sessions. One paper addressed DDR clock jitter, which many oscilloscopes can analyze based on a long acquisition of clock transitions. However, ensuring that the DUT performs correctly with worst-case jitter is a different problem. By triggering only on the widest or most narrow clock cycles, the DUT performance was monitored under worst-case conditions.

Power integrity is particularly important in today’s vehicles with as many as 100 electronic control units. ZUKEN’s RLC-based CR-5000 Lightning Power Integrity Advance software provides a fast and accurate alternative to a full-wave solver, allowing car designers to work more efficiently because the CR-5000 approach can be inserted early in the design flow.

Decoupling capacitors are a traditional feature of digital circuits, but what about capacitance formed between PCB layers? Embedded capacitance can be beneficial at high clock rates, but one technical paper evaluated the interaction between discrete capacitors and intralayer capacitance, showing that resonant problems can occur. Farad-Flex makes very thin high-C substrate material intended to be used in place of ordinary FR4 to provide higher embedded capacitance in a multilayer PCB.

Members on an “Ask the Experts” panel session commented on optical transmission for signals faster than 25 GHz. And, automotive applications can be particularly challenging because they mix traditional electromechanical components with sensitive low-V/low-I devices.

Products and Services

More than 100 companies were represented in the product expo that is part of the symposium program. For example, Thermo-Fisher Scientific was there with a new 15-kV or 30-kV discharge gun that is battery powered with optical fiber output to a PC. MiCOM Labs performs automated real-time wireless testing using Boonton power sensors. Com-Power provides microwave antennas with a closely attached preamp. Newtons4th has developed a range of AC power sources. Ophir RF now offers amplifiers that better match common EMC test frequency ranges and power levels. ETS-Lindgren added the EMPOWER Model 7002-006 ETSI-compliant RF power meter. And Teseq (an AMETEK company) launched several products including high-voltage LISNs, the AS0104-800/400 dual-band amplifier, and the NSG 4060 low-frequency immunity test system.

Of the several after-hours events held throughout the week, I attended the 7layers test lab tour sponsored by ETS-Lindgren. The lab is part of the Bureau Veritas group of companies and specializes in cell phone testing. Lab personnel are members of CTIA committees and have been instrumental in developing hand and arm phantoms for more realistic phone testing.