Conformity Magazine - April 2008 - (Page 31)

Average power of up to 13.5 dBm can be higher than 20 dBm peak with such low duty cycles. Example 3b: 2.4 GHz Digitally Modulated Spread Spectrum Systems (other than FH system) The limit is specified as the maximum power spectral density (PSD) in both standards as seen in Table 3b. It is fully or partly a conducted measurement in both cases. The FCC specifies both conducted and radiated power, but ETSI specifies a method of measurement ([6], sec. 5.7.3, step 4), which takes into account the antenna gain and the transmission duty cycle in addition to the conducted power output D measured in zero span (which is essentially the peak power). This is different from FH case above, where conducted power A is average power. Moreover, in case of a directive or high gain antenna, the allowed PSD magnitude “D” must be reduce to satisfy limits. The duty cycle in case of non-FH systems is another parameter that requires further consideration. The FCC however allows 1W maximum conducted power into the antenna, which is easier to measure and control. Comments The PSD can be calculated as Ppsd = Pa / Δf, where Pa is the average power in the Δf frequency band. The FCC stresses narrow band power control while ETSI stresses wideband control, thus allowing higher narrow band excursions. The antenna size would be same as in above case around λ/10 at such frequencies, and similar system performance would be expected with respect to transmitted power. Conclusions The transmitted power limits and measurement methods for LPDs/SRDs with respect to North American and EU requirements has been studied, and some variation in the definitions of power measurement terminology, such as ERP, EIRP or e.i.r.p., used by the regulatory bodies has been noted. Equipment designers should take note of regulatory requirements of the target market regions, and strive for compliance by taking into account the power measurement methods being used in the respective regions. Inam Rahim is with Intelligent Mechatronic Systems, Inc., and can be reached at irahim@intellimec.com. References 1. 2. Federal Communication Commission CFR 47 rules FCC part-15 sub part C. Industry Canada “Low power License Exempt Radiocommunication Devices Cat. 1 Equipment”, RSS-210, Sept. 2005. ERM, “EMC Standard for Radio Equipment and Services Part 1: Common Technical Requirement”, ETSI EN 301 489-1 4. ERM, “Short Range Devices (SRD); Radio Equipment to be used in 25 -1000 MHz range with power levels up to 500 mW”, ETSI EN 300 220-1 ERM, “Cordless Audio Devices in the range 25 MHz to 2000 MHz”, ETSI EN 301 357-1 ERM; Wideband Transmission Systems; Equipment Operating in 2.4 GHz band and using Wideband Modulation”, ETSI EN 300 328 “Radio Disturbance and Immunity Measuring Apparatus – Conducted Disturbances”, CISPR 16-1-2 “Radiated Power and Field Strength from UHF ISM Transmitters”, Larry Burgess”, High Frequency Electronics, Nov. 2006. Summit Technical Media LLC. “Cellular Handset Antenna Efficiency Measurements Using the Wheeler Cap”, White paper, Skyworks Solutions Inc. April 2007. 5. 6. 7. 8. 9. 10. “A Local Government Official Guide to RF Safety: Rules, Procedures,& Practical Guidance”, Appendix A, line #17, June 2000 FAST Link www.conformity.com/1640 3. April 2008 Conformity 31 http://www.conformity.com/1640 http://www.okaya.com http://www.okaya.com

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Conformity Magazine - April 2008 NewsBreaks Editor’s Note Mandatory Analog Cellular Service Ends FCC Releases Quarterly Reports on Consumer Inquiries and Complaints New Standards List Released for The EU’s Low Voltage Directive FDA Issues Notification on Unretrieved Device Fragments FDA Offers Guidance on Waivers for In-Vitro Diagnostic Devices ESD Open Forum Emerging Issues in Standards Challenges in Testing Design Fundamentals Focus on... New Products Product Reviews Premarket Approval Application Guidance Issued by FDA New Jersey Enacts Electronic Waste Recycling Regulations A New U.S. Standard for Workstation and Computer Design Might the CPSC Hold Retailers Accountable for Safe Products? CPSC Loses “Sole Toy Tester” CPSC Actions in the News IEC Standards Update 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 - April 2008

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