Gain Compression (Graph Traces)

Gain Compression shows the Gain versus the stimulus magnitude. Each point in this trace is a combination of a stimulus and a response data point. The x-axis value of the point is the magnitude of the stimulus voltage, and the y-axis value is the ratio of the stimulus and response voltage magnitudes. By default, the axes are shown in dB units. This can be changed through the Trace Format tab.

When Compensation is enabled, the differential EVM (DEVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format.) and the Delay between stimulus and response are shown at the bottom of the trace.

Each point in this trace has an underlying time value, which can be seen by placing a marker on a point. The time value corresponds to the time values in other Graph traces with the same Graph Settings. This means that you can place couple markers between Graph traces to view corresponding events. For example, you could place a marker on an outlier in an AM/AM trace and view the corresponding point in the Delta EVM Time trace. Then, to match the point back to the original stimulus trigger point, for example, you could set the Time Reference parameter to Stimulus so that Marker Coupling would be correct between the Delta EVM Time trace and the original Stimulus Data.

More information about the data in this trace can be viewed in the Graph Results panel.