EMC Society Outreach to Microwave Theory and Techniques Society (MTT-S)

The EMC Society took a positive step towards reaching out to other IEEE Societies by scheduling and presenting a day-long Workshop on “EMC Aspects of Wireless Technology and Cell Phone Packaging.” This workshop was presented Monday, January 8th, 2007 at the 2007 IEEE Radio and Wireless Symposium held at the Long Beach Convention Center in Long Beach, California. This was only the second year this particular Symposium was held and it was selected for the outreach attempt because of its potential fit with EMC and because it was sponsored by MTT-S and co-sponsored by the Communications Society (ComSoc) and the Antennas and Propagation Society (APS).

The Organizers of the workshop included Andy Drozd, current President of the EMC Society; Karl Varian, immediate Past-President of the Microwave Theory and Techniques Society, and Dan Hoolihan, former President of the EMC Society (1998-1999).

Participants in the Wireless Workshop included (from left) Karl Varian, Raytheon, Organizer, Kevin Slattery, Intel, Speaker, Dan Hoolihan, Hoolihan EMC Consulting, Organizer and Speaker, Dave Case, Cisco, Speaker, Andy Drozd, ANDRO Computational Solutions, Organizer and Speaker, Mike Violette, Washington Labs and ATCB, Speaker, Harry Skinner, Intel, Speaker and Michael Foegelle, ETS-Lindgren, Speaker.

Presentations were given by Harry Skinner of Intel Corporation, Kevin Slattery of Intel Corporation, Michael Foegelle of ETS-Lindgren, Dave Case of Cisco Systems Corporation, Mike Violette of Washington Labs and American TCB Corporation, Andy Drozd of ANDRO Computational Solutions LLC, and Dan Hoolihan of Hoolihan EMC Consulting.
Harry Skinner’s first talk was on “Radio Frequency Interference.” His radios are wireless radios in laptop computers so it becomes an “intra-system interference” issue between the electromagnetic interference from the electronics of the laptop and the sensitivity requirements of the wireless radios in the laptop. In some frequency bands, as much as 90 dB of isolation is required to prevent this “intra-system” interference. In general, interference requirements to prevent disrupting the radio service may be 40 dB lower than those required to meet “inter-system” regulatory electromagnetic interference requirements!
Kevin Slattery continued the workshop by discussing the topic of “Reducing Interference in Notebook Wireless Systems.” His talk highlighted a series of measurements (based on work done by his co-workers Xiaopeng Dong and Jin Shi) and investigations into antenna placement on laptop lids and simulations of lid resonances. The measurements used both magnetic field scanning and electric field scanning to characterize the source-noise in the laptop. It was found that by placing an antenna several centimeters away from the resonant structures in the laptop that the interference levels could be lowered by as much as 20 dB. Antenna placement will differ from computer to computer and experimentation is required to find the best position. Recommendations for antenna placement were made at the conclusion of the talk.
The third presenter of the workshop was Michael Foegelle who discussed the topic of “Coexistence of Wireless Technologies in Converged Devices.” In his talk, he defines wireless convergence to be “the growing trend to have multiple radios in one wireless device.” This can be cell phones with Bluetooth, cellular devices with Wi-Fi and Bluetooth, and similar personal electronic devices with multiple wireless-radio capabilities. Michael also defines wireless coexistence to be “the general topic of multiple wireless technologies working harmoniously (i.e., without interference) in the same environment.” Many tests can be performed on the radios in wireless devices by using conducted measurements; however, in the end, determination of the actual performance requires radiated testing. Interference in converged devices can occur in the communication frequency band or in the receiver circuitry. Standards are beginning to be developed and could affect device performance. As the number of radios in any one device proliferate, the engineering challenges to interoperability will increase significantly.
The fourth topic of the workshop was “Evaluating the Impact of RFI on WLAN/WWAN Performance” and was presented by Harry Skinner and based on work done by Harry and his co-worker Anh Dang. WLAN is Wireless Local Area Network and refers to technologies that are unlicensed. WWAN is Wireless Wide Area Network and refers to technologies that are licensed radios. A comparison of throughput performance was made by measuring a wireless card only and then measuring a wireless card plus a PCIe video graphics card. The comparison showed a degradation of 2 to 3 dB for WLAN due to the 6th harmonic of the PCIe memory clock. It was also found that the Total Isotropic Sensitivity of a WWAN device can be negatively affected by clock harmonics and this could block the wireless device from being accepted by the wireless carriers.
Kevin Slattery gave his second talk of the workshop and it addressed the topic “An Analysis of Digital Display Frame Symbols and Their RFI Potentials.” The objective of the talk was to develop a method for determining EMI/RFI impact in advance of system measurement. The purpose of this would be to select a set of display symbols to minimize their EMI/RFI impact by coordinating their bit structure. It was found that there could be as much as 30 dB difference between the interference potential of clock harmonics, display symbols, and pseudo-random bit streams (PRBS). By realizing that different symbols produce different spectral peak distributions, a Fourier series components of signal symbols can be ordered to reduce the EMI impact. Measurement results utilizing this theory matched the theoretical results closely. It was also found that differential signals can reduce the EMI impact, but only if the intra-pair skew is minimized.
The first speaker of the afternoon was Dan Hoolihan who spoke on “EMC and Telecommunications: A Regulatory Review.” This topic was introduced by drawing comparisons between the similarities and differences of EMC testing and Telecom testing. A brief history of the Federal Communications Commission led into a description of Telecom Certification Bodies in the USA. This was followed by a brief review of Canadian, European, South American, and Asian telecom regulations. Finally, the basic measurement parameters for general FCC telecom testing were analyzed including RF Power Output, Modulation Characteristics, Occupied Band Width, Antenna Terminal Spurious Emissions, Radiated Spurious Emissions, and Frequency Stability with temperature and voltage.
Dave Case followed with a presentation on “A Look at the 4.9 GHz Public Safety Band.”
This topic has received expanded attention since “9/11” and “post-Katrina” difficulties with public safety officials communicating with one another in emergencies. The US government set aside a frequency band for broadband wireless for Public Safety; it selected the 4940-4990 MHz frequency range on a licensed basis. Two emission masks to mitigate interference were specified by the FCC in order to allow present-day IEEE 802.11 technology and still cover higher-power systems. Canada has adopted similar regulations and other countries around the world are looking at the 4.9 GHz band for Public Safety needs.
The next presentation was given by Mike Violette and was entitled “Twists and Turns on the Road to Wireless Compliance.” In this talk, Mike covered the evolution of EMC testing from the 1980s with its emphasis on FCC compliance of Personal Computers, the 1990s with the European influence on commercial immunity testing, and the 2000s with wireless certification and integrated EMC/wireless testing. This has resulted in the EMC test lab seeing an increased complexity in the tests it runs leading to the need for an expanded test equipment inventory. Wireless technologies that are commonly measured include WiFi, Broadband over Power Line, RFID, Ultra Wide Band, frequency-agile transmitters, and WiMax. Challenges to testing for wireless include access to common procedures, setup and operation of the customer’s equipment, failure modes, and disagreement between different parts of the FCC Rules.
The final presentation of the day was given by Andy Drozd and it was titled “Transmission Hyperspace: An Approach for Efficient and Interference-Free Spectrum Management for Diverse Radio Systems and Cellular Communications Equipment.” In his presentation, Andy discussed spectrum policy reform, emerging technologies (such as Software Designed Radio), jointly optimized transmission hyperspace, and computer simulation of spectrum management domains. Current spectrum management policy is based on narrowband analog signals; and, it has very little meaning for more modern wideband digital systems. Both the FCC, with its spectrum policy task force, and DARPA, with its XG program, have started to investigate a more efficient use of the electromagnetic spectrum. The IEEE 1900.x projects are also looking at standards for the next generation of radio and advanced spectrum management. Andy defined a Transmission Hyperspace to be “an electromagnetically occupied volume bounded in all dimensions including time, space, frequency diversity, code/modulation/waveform diversity, polarization, power budgeting, and smart antenna directivity.” Using a “Challenge Problem” simulation concept, it was shown that a better than 20 times performance improvement of the spectrum transmission could be achieved.

The workshop presented at the MTT-S 2007 IEEE Radio and Wireless Symposium was similar to a workshop with a similar title given at the 2006 IEEE International Symposium on EMC in Portland, Oregon. The workshop presents important ideas on challenges of EMC and wireless devices as their size shrinks and their “radio” capabilities expand. It is hoped to give a similar workshop at the 2007 IEEE International Symposium on EMC in Hawaii in July of 2007. EMC

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