Conformity Magazine - October 2008 - (Page 39)

F ew environments present electromagnetic compatibility (EMC) situations as extreme as those faced by designers and manufacturers of radio-frequency (RF)/microwave amplifiers. Substantial efforts must be made to ensure that the signals observed are amplified or generated by the equipment being designed and manufactured, rather than radiated by unknown equipment and amplified by the equipment under test. In some cases, it may also be necessary or desirable to minimize the interference imposed by some of the products under test upon common wireless devices in the vicinity. For example, it is possible for a mobile phone power amplifier (PA) manufacturer who tests devices using actual or simulated mobile signals to interfere with real mobile phone signals in the proximity of the test area, which is not only inconvenient but possibly illegal. This article examines some of the effects of electromagnetic interference (EMI) in extreme environments, and discusses some methods that can be used to mitigate the occurrences, as well as some issues that must be avoided. RF, RF Everywhere If humans were able to detect RF and microwave radiation as visible light, it would appear that the entire world is illuminated, virtually everywhere, all the time. The explosive growth of the wireless revolution has resulted in an almost incalculable amount of wired and wireless devices that radiate intentionally and often unintentionally in the RF and microwave spectrum, at frequencies ranging from a few tens of kHz to almost 100 GHz. This proliferation of wired and wireless devices is most dense in populated urban environments, but is substantial as well in rural and even remote locations. The presence of even one human almost guarantees some kind of RF signature. This level of RF intensity includes spectral output from intentional radiators, like cell phones and computers with WiFi, as well as unintentional radiators, like electric motors, fluorescent lamps, and digital devices. Add to this the number of devices that are only intended to receive (at this point in time) signals from remote transmitters (radios, televisions, global positioning system (GPS) receivers), and it becomes evident just how pervasive the RF presence is. As an example, Table 1 lists the electronic devices within the author’s office (five feet), surrounding company office space (5-50 feet), and adjacent lab (50500 feet). Power amplifier product development and testing are done in the lab; until one sits down and takes stock of the surrounding environment, it is easy to overlook the fact that over one hundred possible sources of interference exist in the form of everyday electronic tools. In the presence of so much intentional and unintentional electromagnetic radiation, how do electronic product designers and/or manufacturers ensure freedom from interference, proper operation, prevention of damage, minimization of data loss, and so on? Add to these issues the myriad of modulation techniques, from orthogonal frequency-division multiplexing (OFDM) and code division multiple access (CDMA), to Gaussian minimum shift keying (GMSK) and quadrature phase-shift keying (QPSK) or other quadrature amplitude modulation formats, and the possibilities for unanticipated, untested interference are, literally, endless. Various power levels, frequencies, code formats, and burst rates from devices that are unable to communicate and coordinate with one another create unlimited opportunities for interference. http://www.nec-tokin.com/english/ http://www.nec-tokin.com/english/

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Conformity Magazine - October 2008 Contents Editor's Note FCC Releases Annual Report on National Do-Not-Call Registry Commission Cracks Down (for the Fourth Time!) On Junk Fax Marketer FCC Releases Quarterly Reports on Consumer Inquiries and Complaints Greenpeace Ranks Electronics Manufacturers Standards List For The EU’s Energy Consumption Directive Published EU Commission Publishes Standards List for Directives on Pressure Equipment, Pressure Vessels Standards List for the EU’s Medical Devices Directive Available The IEEE Product Safety Engineering Society: The First Five Years ESD Open Forum Improving Election Security and Accuracy: The Future of Voting System Certification Conformity Assessment and Accreditation: Their Role in the Global Market Design Issues in Extreme EMC Environment Focus On... Test Equipment Buyers Guide Product News Updated Standards List for EU Directive on Active Implantable Medical Devices FDA Warns of Effects from CT Scans on Electronic Medical Devices FDA Provides Report Card on Its PMA Review Process CPSC Releases Import Safety Strategy Other CPSC Actions in the News IEC Standards Update Product Reviews UL Standards Update Telcordia Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - October 2008

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