Method for Estimating Electromagnetic Interference due to Unbalance in Telecommunications Line


IEICE TRANSACTIONS on Communications   Vol.E75-B   No.3   pp.141-147
Publication Date: 1992/03/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Measurements and Control of Electromagnetic Interference)
interference,  EMC,  EMI,  common mode,  unbalance,  telecommunications line,  

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Information technology equipment connected to telecommunications line can be a source of electromagnetic interference. Two sources of interference have been under evaluation. One is the digital pulses in the switching regulator and the clock oscillator, and the other is the signal's common mode voltage. In this paper, the interference-inducing mechanism for the signal's common mode voltage and a method for measuring the interference are described. An equivalent circuit representing both the equipment and the line is derived on the basis of the interference-inducing model. A method for estimating the signal's common mode voltage from the differential mode voltage and the line unbalance is obtained using the equivalent circuit. It is confirmed that the level difference between the estimated and the measured common mode level is less than 3dB.