Click here to purchase the entire book in PDF format. Phase Response The phase response of a DUT is similar to the frequency response, with the exception that we are now looking for a change in phase of a signal at various frequencies rather than a change in gain. It is measured by again, comparing the input of a DUT to its output at various frequencies. There are frequently cases when the total delay of the DUT must also be considered in making a phase response measurement as in the case of AD and DA conversion. Phase response measurements are usually graphed similarly to frequency response measurements, on a semi-log graph, showing frequency on the X-axis and phase on the Y-axis. The phase will usually be plotted in degrees, either wrapped or unwrapped. If the phase is wrapped, then the graph is limited from -180$^{\circ }$ to 180$^{\circ }$. any phase measured to be outside of that window is then wrapped around to the other side of the window - for example, -190$^{\circ }$ is plotted as 170$^{\circ }$, since 190$^{\circ }$ behind and 170$^{\circ }$ ahead will have the same result. If the plot is unwrapped, the phase will be plotted as measured.