Keysight EXG and MXG X-Series Signal Generators User’s Guide 209
Basic Digital Operation for N5172B/82B with Options 653/655/656/657
Setting the Baseband Frequency Offset
DAC Over–Range Conditions and Scaling
When using the baseband frequency offset (at a setting other than 0 Hz), it is possible to create a
DAC over–range condition, which causes the Keysight MXG/EXG to generate an error. To minimize
this condition with the frequency offset feature, the Keysight MXG/EXG incorporates an automatic
DAC over–range protection feature that scales down the I/Q data by 1/square root of 2 when the
offset is something other than zero. Because it can scale the data by more than what is actually
need, it typically decreases the dynamic range of the waveform. This is especially noticeable when
using a constant amplitude signal such as GSM.
For the Dual ARB Player, this automatic over–range feature can be turned off. When on, it is active
for the Dual ARB signal only when the offset is something other than 0 Hz. The control for the Dual
ARB DAC over–range protection feature is located in the key path as shown in Figure 8-14.
Modulated carrier with 0 Hz
baseband frequency offset
Modulated carrier with 20 MHz
baseband frequency offset
Modulated RF signal
LO/carrier feedthrough
Spectrum analyzer set to a span of 100 MHz
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