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Method for Characteristic Impedance Measurements of Coaxial Cables

IP.com Disclosure Number: IPCOM000040541D
Original Publication Date: 1987-Nov-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Costa, NS: AUTHOR

Abstract

This article relates to the field of measurement techniques. Its achievement is to have a precise, repetitive way to have a coaxial cable characterized according to its electrical properties, instead of using the known approach of measuring the Velocity of Propagation by resonating the coaxial cable sample under test (SUT) with its far-end left as an open circuit which leaves space for erratic measurement errors. The present methods in use generally deal with low frequency capacitance measurements or time domain reflectometry, being strongly dependent on the sample's far-end status, frequently left open or short circuited, consistently presenting non-repeatable results.

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Method for Characteristic Impedance Measurements of Coaxial Cables

This article relates to the field of measurement techniques.

Its achievement is to have a precise, repetitive way to have a coaxial cable characterized according to its electrical properties, instead of using the known approach of measuring the Velocity of Propagation by resonating the coaxial cable sample under test (SUT) with its far-end left as an open circuit which leaves space for erratic measurement errors. The present methods in use generally deal with low frequency capacitance measurements or time domain reflectometry, being strongly dependent on the sample's far-end status, frequently left open or short circuited, consistently presenting non-repeatable results. Furthermore, the final measurement objective, which is the coaxial cable's characteristic impedance, is calculated by using the cable's capacitive value as measured at a frequency of 10 kilohertz, completely unrelated to the field cable's usage, which ranges from 10 to 400 megahertz. Thus, the calculation of the characteristic impedance suffers from two error sources, as mentioned. To contour those two error sources, it would be necessary to measure the SUT at the range that it is to be used in the field and to grant that the electrical measuring circuit is as good as possible, similar to field application. To achieve those objectives, we proposed the SUT loading with its characteristic impedance, thus providing a perfect electrical matched circuit which simulates the field application, a...