Browse Prior Art Database

Line Impedance Stabilization Network

IP.com Disclosure Number: IPCOM000083393D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 36K

Publishing Venue

IBM

Related People

Bunch, AD: AUTHOR [+2]

Abstract

Line impedance stabilization networks (LISN's) are commonly used for measuring radio-frequency impedance (RFI) noise conducted on the input power lines of equipment. The purpose of the network is to provide a known impedance on the line, with respect to the frequency spectrum of interest. This is accomplished by insertion of a high-series impedance and a low, known shunt impedance at the test pick-off point.

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Line Impedance Stabilization Network

Line impedance stabilization networks (LISN's) are commonly used for measuring radio-frequency impedance (RFI) noise conducted on the input power lines of equipment. The purpose of the network is to provide a known impedance on the line, with respect to the frequency spectrum of interest. This is accomplished by insertion of a high-series impedance and a low, known shunt impedance at the test pick-off point.

This LISN involves the use of ferrite cores F of a particuIar type and shape to surround a solid conductor B of the proper cross-sectional area to handle the desired current. The action of the ferrite F is to inject a high RF impedance on the current carrying conductor. The characteristic impedance of the LISN as seen from the equipment under test, EUT, is set to the desired value by a shunting resistor R connected to ground by a coupling capacitor C1. Noise measurements are made via a coaxial connector connected to the resistor, coupling capacitor junction.

The function of the ferrite core element F around the bus bar B, is to convert the section of the bus bar which it embraces into a high-inductance element in a frequency range commencing well above the power frequency from the AC main connection, and extending continuously to well above the highest frequency of interest in the noise measurement. Decoupling capacitor C2, in conjunction with core F, acts as a filter to screen noise for the AC mains from entering the test...