Average of the Height-Dependent Antenna Factor

Katsumi FUJII  Akira SUGIURA  

IEICE TRANSACTIONS on Communications   Vol.E88-B   No.8   pp.3108-3114
Publication Date: 2005/08/01
Online ISSN: 
DOI: 10.1093/ietcom/e88-b.8.3108
Print ISSN: 0916-8516
Type of Manuscript: INVITED PAPER (Special Section of 2004 International Symposium on Electromagnetic Compatibility)
EMI measurement,  antenna factor,  EMI antenna,  antenna calibration,  method of moments,  

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Theoretical analyses are carried out on the height dependence of the antenna factor of an EMI antenna to develop an antenna calibration method that can provide the free-space value of the antenna factor. It is found that the antenna factor in general varies with the antenna height in a quasi-periodic way with a period of about λ/2. Thus, the present paper proposes to take an average of the antenna factors over a height range of about λ/2 to obtain an accurate estimate of the free-space antenna factor. Effective antenna arrangements are also proposed for the antenna calibration. Deviations in the estimate from the free-space antenna factor are less than 0.1 dB for tuned dipoles in the frequency range above 50 MHz. But the errors increase up to 0.3 dB at about 35 MHz. For broadband antennas, the free-space antenna factor can be accurately estimated by taking the average of the antenna factors. Errors are estimated to be less than 0.3 dB in the frequency range from 30 MHz to 1000 MHz.