2011 EMC Directory & Design Guide - Interference Technology

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standards O n t h e N at ur e a nd Us e of t h e 1.04 m El e c t ric Fiel d Probe On the Nature and Use of the 1.04 m Electric Field Probe Ken Javor EMC Compliance Huntsville, Alabama USA R epeatability problems have been noted with 1.04 m rod antenna measurements in the past (Jensen [1], Turnbull [2]). The problems noted center on resonances caused by the test set-up that result in erroneous measurements of field intensity with actual detected levels varying among test facilities. A complete history of the use of the 1.04 m rod antenna from the 1950s forward and test data showing the effects of different rod antenna use may be found in Javor [3]. Various vehicle-related standards utilize the 1.04 m rod antenna below 30 MHz. Military (MIL-STD-461 basic and all revisions), aerospace (RTCA/DO-160 basic through the E revision), and automotive EMI standards (CISPR 25-2002, among others) all make use of the rod antenna. To date, only MIL-STD-461F (2007) incorporates fixes to the resonance problem. And none of the other standards address the accuracy of the fundamental measurement, at frequencies where resonances are not a problem. Recently, Weston [4] criticized the MIL-STD-461F change. His main points are discussed herein. Analytical modeling supported by experimental investigation shows that a floated counterpoise with transformer coupling between the rod antenna matching network and the test chamber ground provides the best performance at all frequencies. Experimental data shows the unacceptable perturbation caused by a grounded counterpoise. In addition to these particular issues, and as a means of making specific points, the general nature of the rod as an electric field probe, and the transfer function between field source and measured field intensity are explained. INTRODUCTION The 1.04 m rod “antenna” is electrically short at all test frequencies and does not function as a true antenna, which is a transducer that effectively radiates or receives “power” associated with electromagnetic fields. The rod is better understood as an electric field probe or sensor. The output impedance associated with the induced voltage in the rod is the reactance of 10 pF. Networks used with rod antennas are impedance matching devices which convert the rod’s high impedance to a 50 Ohm output. Use of the 1.04 m rod antenna has changed dramatically since its introduction in 1953 (MIL-I-6181B). Original use is shown in Figure 1, with the rod element connected directly to a battery-powered EMI receiver; the only ground connection being a very short bond strap to the tabletop ground plane. The first change allowed remote use of the EMI receiver from the antenna, which made EMI testing more practical, but introduced both a potential ground loop and also a difference in rf potential between the rod counterpoise and the EMI receiver. Another change increased the upper frequency at which the rod antenna was used from 25 to 30 MHz. This, coupled with a later change that increased separation between antenna and test sample from the original 12 inches to the present one meter 66 interference technology emc Directory & design guide 2011
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TM 2011 EMC Directory & Design Guid
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contents2011 Interference Technolog
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from the editor A look back — and
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testing & test equipment sions is a
Page 17 and 18: CPI: Powering your world. TWTAs for
Page 20 and 21: testing & test equipment Troublesho
Page 22 and 23: testing & test equipment Troublesho
Page 24: testing & test equipment Wir e l e
Page 27 and 28: Viol e t t e testing & test equipme
Page 29 and 30: Viol e t t e testing & test equipme
Page 32: testing & test equipment M e a s ur
Page 35 and 36: H o o l ih a n testing & test equip
Page 38 and 39: testing & test equipment O n t h e
Page 40 and 41: New Military Product Highlights IFI
Page 42: testing & test equipment O n t h e
Page 45 and 46: R o drigue z testing & test equipme
Page 47 and 48: R o drigue z testing & test equipme
Page 49 and 50: EMC EMI EMP EMR EMV ESD EMCON HERF
Page 51 and 52: R a da s k y testing & test equipme
Page 60: testing & test equipment N e w EMC
Page 63 and 64: B o r g s t r o m testing & test eq
Page 65 and 66: B o r g s t r o m testing & test eq
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Page 71 and 72: EMI/RFI Shielding Solutions Our ext
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Page 108 and 109: filters A c c ur at e F e e d t hr
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H o f f m a nn, Br aun, Frech, Rus
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design EMI Sources and Their Most S
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Cover_DDG10.indd 1 TM EMC Design ..
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standards recap HBM ESD parameters
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standards recap International Organ
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standards recap noise from power li
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standards recap quality on selected
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standards recap including to addres
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professional societies Every year,
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professional societies of TechAmeri
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professional societies education, s
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government emi/emc directory Mr. Ro
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government emi/emc directory Ms. Ja
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government emi/emc directory Chief:
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products & services index products
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products & services index Electrost
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products & services index Lightning
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products & services index York EMC
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company directory company directory
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company directory AR Tech Engineere
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company directory DARE!! Instrument
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company directory DNK Metric A/S...
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company directory Instruments For I
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company directory Metal Textiles Co
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company directory Protocol Data Sys
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company directory Spira Manufacturi
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company directory VPT, Inc. .......
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