290 N5511A Phase Noise Test System User’s GuideEvaluating Your Measurement ResultsEvaluating the ResultsEvaluating the ResultsThis chapter contains information to help you evaluate and output the resultsof your noise measurements. The purpose of the evaluation is to verify that thenoise graph accurately represents the noise characteristics of your DUT. To usethe information in this chapter, you should have completed your noisemeasurement, and the computer should be displaying a graph of itsmeasurement results. Storing the measurement results in the Result File isrecommended for each measurement.These steps provide an overview of the evaluation process.— Look for obvious problems on the graph such as discontinuity (breaks).— Compare the graph against known or expected data.— If necessary, gather additional data about the noise characteristics of theDUT.Looking for obvious problemsSome obvious problems on a graph are as follows:— Discontinuities or breaks in the graph.— A higher than expected noise level.— Spurs that you cannot account for.— Noise that exceeds the small angle criterion line on a L(ƒ) graph.Figure 14-1 provides a graphical example of these problems. If one or more ofthese problems appear on your graph, refer to “Problem Solving” on page 302for recommended actions.Figure 14-1 Noise plot showing obvious problems
