Prediction of Far-Field EMI Spectrum of Differential Mode Emission from a Digital PCB by Near-Field Measurement

Makoto TORIGOE  Takuya MIYASHITA  Osami WADA  Ryuji KOGA  Tetsushi WATANABE  

IEICE TRANSACTIONS on Communications   Vol.E80-B   No.11   pp.1633-1638
Publication Date: 1997/11/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on EMC Implications of Densely Mounted Electronic Devices)
digital circuit,  EMI,  differential mode emission,  near-field EMI,  far-field EMI,  

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The purpose of this report is to predict far-field EMI spectrum emitted from a signal line on a digital PCB based on near-field EMI measurement. The relation between near magnetic field and far electric field is shown. A method of predicting far electric field from near magnetic field is proposed. Current flowing along a signal line is calculated from measured near magnetic field. Far electric field is estimated from the current. Measurement and prediction of EM emission are carried out using a simple PCB. The result of prediction and measurement of far-field EMI spectrum coincide within the error of 3 dB.