Time domain analysis is useful for measuring impedance values along a transmission line and for evaluating a device problem (discontinuity) in time or distance. Time domain display provides a more intuitive and direct look at the device under test (DUT) characteristics. In addition, it gives more meaningful information concerning the broadband response of a transmission system than other measuring techniques by showing the effect of each discontinuity as a function of time or distance. This document will focus on time domain analysis (displays) generated from vector network analyzers (VNAs). The intent is to provide engineers with frequency domain background, an in-depth view of how a time domain display is created from frequency domain data (S-parameters) and how to apply the time domain display to common problems in RF systems. Agilent offers other documents that cover in detail the use of time domain displays (using data captured with either a time domain reflectometer (oscilloscope) or VNA). See the bibliography for more details.