Communication technologies bring EMC challenges

Some engineers may consider EMC a topic past its prime, but emerging wireless technologies, coupled with the penetration of electronics products into developing countries, are giving the discipline new life. To meet the coming EMC challenges, though, the EMC expertise that's now primarily the domain of older practitioners must become available throughout the electronics industry.

To enhance EMC design prowess and encourage standards conformance, the International Electrotechnical Commission (IEC) has created the Advisory Committee on Electromagnetic Compatibility (ACEC). Its job, according to Dr. William Radasky, chairman of the ACEC, is to apply basic EMC standards to specific types of products.

The ACEC monitors and coordinates EMC standards that individual technical committees produce (Figure 1). The ACEC consults with the various technical committees so they can adopt reasonable and realistic standards. For example, suppose the committee that oversees standards for appliances needs to write an EMC standard for refrigerators. If the committee does not include an EMC expert, members of the ACEC can apprise it about efforts in other committees to handle related EMC problems (see "The IEC and EMC" on the Web at http://www.tmworld.com/emctr).

Radasky sees problems with the mass use of wireless devices using Wi-Fi and Bluetooth technologies. Bluetooth—designed to eliminate cables between peripherals, intelligent appliances, and PCs—has a range of about 10 m. Wi-Fi (IEEE 802.11b) has more range—about 100 m—and is used to implement wireless local-area networks. Wi-Fi installations already provide Internet access in airports, hotels, and coffee shops. Although the market for portable devices is still small, the demand for short-range wireless devices will continue to grow, and as the number of units increases, so will EMC problems.

Although Bluetooth and Wi-Fi devices use different communication techniques and protocols, both types of devices use frequencies in the unlicensed industrial-scientific-medical (ISM) band at 2.4 GHz. Thus, they often end up interfering with one another in large office buildings in which hundreds of wireless devices are simultaneously transmitting (Ref. 2).

While most office equipment can easily tolerate bad packets caused by EMC problems, this is not the case for equipment used in hospitals and medical facilities. Designers of such equipment must more carefully analyze on-site frequency allocations and the implications of EMI and EMC.

At the new George Washington University Hospital (Washington, DC), for example, nurses will use wireless portable computers to chart patients' conditions, physicians will download x-ray images to laptop PCs, and staff members will use wireless devices to communicate by voice (Ref. 3). Facilities such as this may need to adopt their own frequency coordination to keep devices from interfering with one another, and to keep out "foreign" wireless devices brought in by patients, vendors, and visitors.

The IEC has established immunity requirements up to about 1 GHz, but above that, in the frequency ranges used by Wi-Fi and Bluetooth devices, the IEC has yet to develop tests that offer good repeatability. In the absence of such tests, engineers and users have to survey their environment and monitor signal levels to see what's going on at the frequencies they want to use or that could interfere with their equipment. That sort of empirical work may provide a snapshot of today's RF environment, but it may poorly represent a picture of future spectrum use.

The EMC community will have to take precautions until the IEC develops standards and tests to cover the higher frequencies. Until now, frequencies above 1 or 2 GHz were the exclusive domain of military users and experimenters, yet commercial equipment and service providers see this "space" as ideal for the next generation of short-range communications devices. The EMC community, at least in the US, must put more emphasis on potential EMC problems—and solutions—at these higher frequencies.

Overall, the US EMC community seems to spend about 75% of its efforts on testing and regulating emissions, and about 25% of its efforts go toward identifying and fixing EMI and EMC problems. Radasky, who in addition to chairing ACEC works full time as the president of Metatech (Goleta, CA), a consulting company and after-market supplier of EMI filters, feels that many US product engineers don't fully understand immunity and emissions. Many of these engineers think they can overcome problems by simply reducing emissions, but in Radasky's opinion, they also must balance immunity and emissions to reach a compromise that works well when a user installs the equipment.

Radasky says that many industry leaders in the US seem uninterested in EMI and EMC problems, and that upper management isn't technical enough to understand the issues that can have an impact on a company's economic future. As an example of what dedication to EMC issues can achieve, he points to China, still a relatively new supplier of electronics equipment. Overall, Chinese manufacturers have surpassed their US counterparts, he said, having adopted over 50% of the IEC's applicable EMC standards, and they expect to comply with 100% of the standards within three years.

Companies that deal with emissions and immunity must also grapple with the "graying" of their experts and with the small number of EMC-inclined engineers entering the industry. According to Daryl Gerke of Kimmel Gerke Associates (Mesa, AZ), engineering schools concentrate on the glamorous topics of digital design and high-speed analog circuitry. Not many students show an inclination to the "pathology of electronics," as Gerke describes the study of EMC problems, causes, and cures. But the dearth of EMC and EMI training for undergraduates may stem from the lack of experience on the part of students. How can an engineering curriculum include a course on EMC when the students don't have enough design experience to understand the EMC problems and the answers?

At an IEEE EMC chapter meeting in Seattle, Dr. Howard Johnson, a high-speed digital-design consultant, observed a pronounced "baldness effect" among the male members of the group. He concluded most of them were getting close to retirement and that they had spent a lifetime educating themselves in EMC issues. He suggested that digital designers become obsolete after five to seven years, but EMC professionals go on and on (Ref. 4).

These people have gone through a "natural selection" that, according to Gerke, turned them into EMC experts more out of necessity and personal interest rather than as a career path sought in undergraduate or graduate school. Unfortunately, the lack of EMC experts stymies the push of newer technologies into the higher frequency bands, and it curtails the ability of companies to develop new products that can meet current and future immunity and emission standards.