Time-domain reflectometry

US7940056B2 · kind B2 · utility

Assignee

• Radiodetection Limited · GB

Inventor

• Stephen Maslen · Somerset, GB

Key dates

• Filing date: Mar 25, 2009
• Grant date: May 10, 2011
• Expiry date: Jun 30, 2029

Classification

• Technology area (CPC G): Physics
• CPC primary: G01R31/11
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

The present invention provides a method of time domain reflectometry including transmitting a test signal along a cable under test from one end and sensing and recording a reflected signal from the cable at that end, using the recorded, reflected signal to estimate the distance, Ldist, from the one end to a discontinuity on the cable, separating a test signal component from the remainder, Vr, of the reflected signal; estimating the impedance, Zfault, of the discontinuity from known, predetermined values of the characteristic impedance, Zline, and of the characteristic gain, T, of a reference cable, and from the said separated test signal and reflected signal components, calculating the estimation error as a difference between the model reflection signal, Vrmod, expected of the cable under test based on the characteristic impedance and characteristic gain and the estimated impedance, Zfault and distance, Ldist, and the actual reflection signal Vr, choosing new estimated values of Ldist and Zfault in accordance with a predetermined algorithm such as to approach optimal values, repeating the aforesaid step of calculating the estimation error until a predetermined condition has been sa…