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188 Agilent N5161A/62A/81A/82A/83A MXG Signal Generators User’s Guide
Basic Digital Operation (Option 651/652/654) Preliminary
Setting the Baseband Frequency Offset Preliminary
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 Agilent MXG to generate an error. To minimize this
condition with the frequency offset feature, the Agilent MXG 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