192 Keysight CXG, EXG, and MXG X-Series Signal Generators Service Guide
RF Assembly
A3 RF Assembly Overview
The Low Band signal can also be switched to provide the input to the Het Band
block.
Het Band
The heterodyne band block provides output frequencies from 5 MHz to just
below 250 MHz. It generates these frequencies by mixing Synthesizer
Multiplier / Divider section output frequencies of 1.005 GHz to just below 1.25
GHz with the 1 GHz frequency reference from the Reference section. The
resultant IF signal is then filtered and amplified to provide the 5 MHz to 250
MHz RF output signal.
Op-Amp Band
The Op-Amp Band provides output frequencies from 9 kHz to just below 5
MHz. The Op-Amp Band is generated using direct digital synthesis (DDS) from
the Function Generator / Trigger Control section. The DDS module uses the
same 50 MHz clock used as a reference in the Synthesizer section.
There is no ALC loop involved in this path. The frequencies are low enough that
op-amps are used as the amplifiers. These amplifiers have their own feedback
loop and therefore do not need an external control to keep them level over
temperature and time. Digital modulation in not available in the Op-Amp Band.
Output Attenuator
The Output Attenuator block is only in the RF instruments, the microwave
instruments do not have it.
The Output Attenuator block is made up of three different variable electronic
attenuators, Atten 1, Atten 2, and Atten 3. How these are used for the different
overall instrument attenuator settings can be seen in Table 10-3.
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