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Chapter 7 165
Custom Real Time I/Q Baseband
Working with Differential Data Encoding
Using Differential Encoding
Differential encoding is a digital-encoding technique that denotes a binary value by a signal change rather
than a particular signal state. It is available for Custom Real Time I/Q Baseband mode. It is not available for
waveforms generated by Arb Waveform Generator mode.
The signal generator’s Differential State Map editor enables you to modify the differential state map
associated with user-defined I/Q and user-defined FSK modulations. In this procedure, you create a
user-defined I/Q modulation and then configure, activate, and apply differential encoding to the user-defined
modulation. For more information, see “Understanding Differential Encoding” on page 160.
This section includes information on following:
• “Configuring User-Defined I/Q Modulation”
• “Accessing the Differential State Map Editor” on page 166
• “Editing the Differential State Map” on page 166
Configuring User-Defined I/Q Modulation
1. Press
Preset.
2. Press
Mode > Custom > Real Time I/Q Baseband > Modulation Type > Define User I/Q > More (1 of 2) >
Load Default I/Q Map > QAM > 4QAM.
This loads a default 4QAM I/Q modulation and displays it in the I/Q Values editor. The default 4QAM I/Q
modulation contains data that represent 4 symbols (00, 01, 10, and 11) mapped into the I/Q plane using 2
distinct values (1.000000 and −1.000000). These 4 symbols will be traversed during the modulation process
by the symbol table offset values associated with each symbol of data.