Time‐Domain Reflectometry Analysis

The technique of Time-Domain Reflectometry Analysis (TDR) is used to analyze the propagation in the time domain of impulses and echelons in circuits. It enables the measurement of impedances of cables and lines in high-speed buses and identify terminal PCB impedances. It can also be used for the localization and identification of defects or discontinuities on PCB, but requires control of the rise time degradation. The precision of measurements, particularly spatial resolution, depends mainly on the rise time of the signal used. TDR spatial resolution can be defined as the minimum distance between two discontinuities enabling them to be distinguished by reflectometry. It depends mainly on rise time. In fact, on the time scale, the two discontinuities are separated by the round-trip time. Therefore, the separation of two discontinuities requires a minimum distance.