Conformity Magazine - October 2008 - (Page 40)

Effects of EM Proliferation on the Environment The ubiquitous presence of RF and microwave signals manifests itself in multiple ways upon the environment. Perhaps the most noticeable and prevalent of these is the increase in ambient noise levels (for a detailed discussion of noise, see the Burr-Brown Design Seminar on Noise and Interference1). Noise is present in all environments, with the power predictable by the formula kTB, (Boltzman’s constant multiplied by the temperature multiplied by the bandwidth over which the noise power is measured2. This thermallygenerated noise is a natural physical occurrence, which limits the lower power level with signals that can be discerned. With the proliferation of electronic devices, the local noise floor may be much higher than the thermal noise floor, effectively “jamming” some types of communication. While regulatory agencies do their best to define and regulate the amount and frequency of electronic emissions through frequency licensing and equipment performance limitations, these regulations Within 5 feet Laptop computer w/WiFi Dual band mobile phone Bluetooth wireless mouse Bluetooth wireless keyboard Numerous USB flash drives USB camera Land-line digital phone Personal digital assistant (PDA) Fan Fluorescent lamp Wireless key fob AC power supply for laptop 5 - 50 feet Wireless network router Network server Wireless and wired thermostats Coffee maker Refrigerator Water heater/chiller Document shredder Hearing aids Wireless headphones Six automobiles Alarm system Printers Fax machine Scanner Numerous mobile phones Two additional PDAs Numerous fluorescent lights Two microwave signal sources unfortunately must acknowledge the limitations of practical electronic equipment. While limits are placed upon the amount of power that may be radiated to accommodate practical circuitry, the power, even though low, still propagates. This “artificial” noise floor manifests itself in different ways. Within desired operational bands, the additive radiated noise of a particular product appears with similar characteristics of the natural noise floor, just at a higher level. Any amplification will magnify the natural thermal noise signature and contribute an additive amount of noise related to the characteristics of the device. These amplified, radiated noise levels are usually extremely low in practice, so it often is not obvious that they affect other equipment. As shown in Figure 1, communications signal modulation can appear as noise to other equipment that is not specifically configured to receive or accept that modulation. CDMA mobile telephony is a good example. The multiple overlapping 50-500 feet 900 MHz GSM LNAs XC band TVRO block down converter 2-20 GHz 20 watt Spatium power amplifier Two network analyzers Power meter Two spectrum analyzers Soldering irons More fluorescent lights Chest freezer Numerous automobiles Exterior lighting Cell phone reseller Six high temperature environmental ovens LPK prototype board builder Refrigerator Water cooler Printer Numerous computers w/monitors and keyboards Several PCs w/monitors, mice, keyboard (some wireless) 900 MHz 30 watt amplifiers Two 500 watt 170 MHz power amplifiers Wirebonder HVAC unit Soldering irons Network analyzer Two power supplies Telephone PBX system Table 1: Electronic devices in close proximity to the author’s desk generating RF signals that are potential sources of interference. 0 Conformity oCtober 2008

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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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