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Chpater 6 153
Custom Arb Waveform Generator
Working with Symbol Rates
Working with Symbol Rates
The Symbol Rate menu enables you to set the rate at which I/Q symbols are fed to the I/Q
modulator. The default transmission symbol rate can also be restored in this menu.
• Symbol Rate (displayed as Sym Rate) is the number of symbols per second that are transmitted
using the modulation (displayed as Mod Type) along with the filter and filter alpha (displayed as
Filter). Symbol rate directly influences the occupied signal bandwidth.
Symbol Rate is the Bit Rate divided by the number of bits that can be transmitted with each
symbol; this is also known as the Baud Rate.
• Bit Rate is the frequency of the system bit stream. The internal baseband generator (Option 602)
automatically streams the selected Data Pattern at the appropriate rate to accommodate the
symbol rate setting (Bit Rate = Symbols/s x Number of Bits/Symbol).
• Occupied Signal Bandwidth = Symbol Rate x (1 + Filter Alpha); therefore, the occupied signal
bandwidth is dependent on the filter alpha of the Nyquist or Root Nyquist filter being used. (To
change the filter alpha, refer to the procedure, “Adjusting the Filter Alpha of a Predefined Root
Nyquist or Nyquist Filter” on page 147.)
To Set a Symbol Rate
1. Press Preset.
2. Press
Mode > Custom > ARB Waveform Generator > Digital Mod Define > Symbol Rate
or
Mode > Custom > Real Time I/Q Baseband > Symbol Rate
3. Enter a new symbol rate and press Msps, ksps, or sps.