Symbol Rate Error - Agilent Technologies ESA-E Series User And Programming Manual

Making Modulation Analysis Measurements
Interpreting Measurement Results

Symbol Rate Error

Small deviations in the symbol clock can result in significant
modulation errors. Even a small error in symbol rate causes a large
increase in peak EVM, and is indicated by a spreading of the symbol
decision points.
Large symbol rate errors will result in the receiver not being able to
demodulate the signal. The Modulation Analysis Personality is most
useful in troubleshooting small symbol rate errors. To troubleshoot
circuits with large symbol rate errors, try using the ESA occupied
bandwidth measurement function to view the signal channel
bandwidth. You can roughly approximate the symbol rate using this
method.
1. Use the I/Q polar constellation diagram first to identify symbol rate
errors. Press
errors is shown in
decision points and large values of EVM. A symbol rate error of
0.0015 Msps over the actual symbol rate was used to obtain this
result.
Figure 4-21 Polar Constellation Showing Symbol Rate Error
42
I/Q Measured Polar Constln
Figure 4-21. Note the spreading of the symbol
. A signal with symbol rate
Chapter 4