Conformity Magazine - September 2007 - (Page 17)

reflections and cable reflections, and assumed the radiation aperture is known. Measurement Results Determination of the Time Gate Determination of the time gate was critical in obtaining clean and accurate results. Errors can occur when too much of the data waveform has been truncated. Familiarization with the antenna waveform shape and experimentation with different gate times will reduce this error. Figures 4(a-c) show time-domain waveforms of the three antennas measured at different separations. Nominal times used for gating in this investigation are given in Table 1. Ray-tracing was used to find the direct and ground plane reflected paths. Path times for the direct and primary reflected signal wavelets are given in Table 2. A one ns/ft ratio was used to obtain these values. Upon examining Figures 4(a-c), it can be seen that the DRG has a fairly clean antenna waveform for all the distances measured; due to its relatively short ring-down time. However, the analysis for the two lower frequency antennas is not so simple. Their longer ring-down times cause the direct and ground reflected signal waveforms to be intermingled at the longer separation distances. This required a slight shortening of the time gates for these configurations to obtain usable time-gated data, but with slightly larger errors. The biconical also exhibited an additional time delay when compared to the Figure 5: Comparison of (a) ungated and (b) gated AF differences for the DRG antenna Figure 6: Comparison of (a) ungated and (b) gated AF differences for the large DRG antenna September 2007 Conformity 17 http://www.amphenol-aerospace.com/filtercatalogs http://www.amphenol-aerospace.com/filtercatalogs http://www.amphenol-aerospace.com http://www.amphenol-canada.com

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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