A METHOD TO ESTIMATE NORMAL-MODE NOISE VOLTAGE INDUCED ON INDOOR TELECOMMUNICATION LINES DUE TO ADJACENT AC SUPPLY LINES

When metallic telecommunication lines carrying digital signals are lai d adjacent to sc supply lines in an office or a house, then the noise generated by the ac supply lines is induced on the telecommunication l ines and the quality of transmission may be degraded. To calculate the induced voltage generated directly between the cores of a telecommuni cation line requires accurate values of the coupling admittance or cou pling impedance between the two lines corresponding to the cable const ruction and the problem becomes very complicated. This paper proposes a simple method of estimating the voltage induced between the cores of a telecommunication line when the telecommunication line is laid adja cent to an ac supply line. The amount of coupling from the primary cir cuit with an open-circuited terminal and with a short-circuited termin al to the secondary circuit is measured. Using this value, the charact eristics of the induced voltage corresponding to an arbitrary value of terminal impedance of the primary or secondary circuit simply are est imated. The validity of the estimation method was confirmed by experim ents.