Browse Prior Art Database

Line Impedance Stabilization Network

IP.com Disclosure Number: IPCOM000093273D
Original Publication Date: 1967-Aug-01
Included in the Prior Art Database: 2005-Mar-06
Document File: 2 page(s) / 22K

Publishing Venue

IBM

Related People

Snover, AL: AUTHOR

Abstract

This line impedance stabilization network LISN is placed in series with a transmission line for the purpose of measuring noise or transients on the line. The LISN presents a constant reference impedance, usually 50 ohms, to the transmission line on test over some predetermined frequency range.

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Line Impedance Stabilization Network

This line impedance stabilization network LISN is placed in series with a transmission line for the purpose of measuring noise or transients on the line. The LISN presents a constant reference impedance, usually 50 ohms, to the transmission line on test over some predetermined frequency range.

The LISN components function as follows. The 0.1 microfarad ceramic capacitor 1 decouples the noise to be measured from the transmission line under test and presents it to coaxial output connector 2. At the latter point, a 50 ohm measuring instrument is attached. Small metallic plate 3 is fastened parallel to one side of capacitor 1 to improve the high-frequency response. Ferrite cylinders 4 are placed over the transmission line under test to form a high-impedance loss transmission line.

The high impedance prevents the total impedance presented to the machine on test from being distributed by the power input end of LISN. The electrical loss involved in the ferrite material prevents unwanted noise on the power input end from disturbing the measurement being made. Cylinders 4 can be adjusted to tune LISN for optimum high frequency response. A 1.0 microfarad decoupling capacitor 5 provides further isolation from the input power and filters out the power line noise. Coaxial output lead 6 can be used in special packaging methods so that individual LISN sections can be directly connected to standard power connectors.

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