Ideal State (Digital Demod)
provides the location of all ideal states in an IQ or constellation diagram.
Shape
in Ideal State specifies how the ideal states are represented on the trace: a cross, circle, or none.
Ideal States are not shown for trace data for or demodulation.
When Cross is selected, the ideal state occurs at the center of the cross. For Circle, the ideal state occurs at the center of the circle.
The ideal state is where symbols occur if the signal is without error. Showing the ideal states gives a visual indication of the quality of the signal.
Size
IQ trace results are normalized differently for different demodulation measurement standards and modes. The relationship between the percentage units in this property, and EVM 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. assumes an IQ constellation where the unit circle (magnitude 1.0) is used for normalization of the EVM measurement. In cases where a different normalization is used, the direct relationship may require scaling this value. The Error Vector trace results with a points per symbol setting of 1 are often better suited to identifying EVM distribution in these cases.
in Ideal State allows the size of the shapes to be adjusted. An ideal-state EVM (Error Vector Magnitude) can be specified from 0.1% to 50%. The value entered determines the radius of the ideal-state circle or size of the ideal-state crosshair.
This feature can be used to determine if symbols have an EVM above a specified value. For example, to see if any symbols have an EVM greater than 10%, set the state size to 10% and display the ideal state as a circle. Any symbols that fall outside of the circle (other than SYNC or PILOT symbols) have an EVM greater than 10%.
See Also
