Virtual signal‐integrity verification tool for copper twisted‐pairs using TDR

Abstract

Time-domain reflectometry (TDR) is an important technique for verifying the impedance and quality of signal paths in components, interconnects, and transmission lines. However, the success of channel condition assessment through on-site interpretation of TDR echoes hinges on the skill and experience of the operator. This study presents a TDR simulator to assist loop diagnostics on copper twisted pairs widely used in current digital subscriber line (DSL) access networks. The simulator is developed based on established frequency-dependent cable models to synthesise realistic TDR echoes arising from various cable discontinuities. Modelling of arbitrary loop configurations and faults is accomplished by cascading multiple sub-lines with different characteristics through ABCD parameters modelling. The usability of the simulator is enhanced using a graphical user interface and its accuracy has been verified experimentally using TDR echoes obtained from commercial TDR testers. Since lengthy twisted pairs are deployed in real DSL access networks, the TDR simulator can be used to perform on-site simulation and verification during DSL network maintenance and troubleshooting, as well as to gain mastery of TDR handling while circumventing the need for bulky and costly cabling test beds. The simulator can also be useful to supplement the teaching of electromagnetics and high-frequency measurement.