Chapter 8 Measure Mode – Basic Tab
Constellation
DSAM Help User Guide Rev. 001 177
Phase Noise
Phase noise impairments cause the dots on the graph to form a
circular pattern possibly caused by faulty modulators. Phase noise is
best seen on the grid without the use of the zoom feature.
Coherent Interference
Coherent interference impairments – such as CTB, CSO, and spurs –
cause the dots on the graph to cluster with an empty space in the
middle.
Figure 159 Constellation – Thermal (system) Noise
Figure 160 Constellation – Phase Noise
Figure 161 Constellation – Coherent Interface
21128026 R001 DSAM Help User Guide.book Page 177 Thursday, February 5, 2009 2:02 PM