Conformity Magazine - September 2007 - (Page 16)

links either transmitted or received the RF power via fiber to minimize signal loss over large distances. A photo of this system is shown in Figure 2 for a typical setup. Data Processing in Time Domain The data were processed in a multiple-step signal processing sequence that permitted the separation of the desired propagation events. This time-domain processing of densely packed data allows for the efficient manipulation of the OATS transmission loss data to corrected free-space values. The signal processing sequence used to quantify the desired propagation events is shown in Figure 3 and is further described in [9]. The procedure can be summarized in four basic steps: 1. 2. 3. 4. Inverse Fourier transform CW magnitude and phase data, S21, to obtain a time-domain data waveform. Time-gate the insertion loss waveform to isolate the direct path propagation from any scattering events. Fourier transform the time-gated waveform of step 2 back to CW magnitude and phase data, S21. Process this time-gated CW insertion loss data using the two-antenna method and Friis equation to determine the free-space antenna factors. To find the FSAF we used Equation 24 from [7]: AF = 10•log (F/d) + ½ [IL + Corr –16.0 ] (1) with Corr = 0 for free space and the insertion loss term (IL) replaced with the time gated value obtained from the time domain signal processing: IL = | FT {IL gated} | (2) In Equation 2, FT denotes the Fourier transform of the enclosed term. This term is now just the direct signal after the reflected data was removed through time-domain processing. We have neglected the contributions of internal antenna Correction In our August issue, the article entitled The Development of CISPR 22 as the Basic International EMI Standard for Information Technology Equipment includes two tables that may be confusing to readers. The tables, which appear on page 20 of the issue, show limits for measurements above 1 GHz, but the headings for the columns “Average” and “Peak” were erroneously reversed. The corrected tables are printed below: We apologize to our readers for any confusion that this error may have caused. Limits for radiated emissions of Class A ITE at a 3m measurement: Frequency Range [GHz] Average [dBμv/m] 1 to 3 3 to 6 56 60 Peak [dBμv/ m] 76 80 Limits for radiated emissions of Class B ITE at a 3m measurement: Frequency Range [GHz] 1 to 3 3 to 6 Average [dBμv/m] 50 54 Peak [dBμv/m] 70 74 Figure 4: (a) Time-domain waveforms for the DRG antennas, (b) time-domain waveforms for the large DRG antennas, and (c) timedomain waveforms for the biconical antennas 16 Conformity September 2007

Table of Contents Feed for the Digital Edition of Conformity Magazine - September 2007

Contents Editor’s Note FCC Extends Disability Access Requirements to VOIP Commission Fines Importer $3 Million Over Non-Compliant TVs FCC Gets Tough on Retailers Over Analog TV Tuner Labeling Analog Cellular Service Sunset Date Reaffirmed Commission Adopts Recommendations of Katrina Panel Free-Space Antenna Factors Through the Use of Time-Domain Signal Processing Editorial Correction ESD Open Forum An Update on Revisions to IEC 61000-4-2, the Basic Standard on ESD Practical Advice for Meeting the DFS Testing Requirements of the FCC The EMC Impact of Embedded Software ESD Design Buyer's Guide Tate Renominated to the FCC EPA Releases Report on U.S. Electronic Waste Additional Standards For The EU’s Toy Directive Medical Device Manufacturer Enters Consent Order Updated Guidance Document on Laser Products Issued FDA Offers Advice on Defective Heating Pads CPSC Issues China Product Safety Program Report Other CPSC Actions In The News IEC Standards Update Product Reviews Product News UL Standards Update From Our “You Can’t Make This Stuff Up” Department Looking Back: Items from Past Issues of Conformity Advertisers

Conformity Magazine - September 2007

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