Question
How is the behavior of the RF port of the signal generator
when the signal definition is changed and
what can be done to minimize the RF level break-in?
Interruptions in the RF level when the signal changes
Answer
In general, the SMU checks for every command received whether the associated
parameter has to be changed or not.
If no change is required, the SMU will do nothing. For example:
The SMU output frequency is 1 GHz. The command "set output frequency to 1 GHz"
is received.
The SMU will not change the setting, but just continue to output 1 GHz.
The procedure is the same for nearly all commands, except a few special ones such as Save/recall.
A change of one of the parameters RF frequency, output power or modulation on/off
might cause an interruption (blanking) of the RF signal.
The signal is blanked, for example, when a hardware component in the RF path has to be switched, e.g.:
- Electronic attenuator (switching points approx. every 5 dB)
- Filters
- Dividers
- RF synthesizer
All modern signal generators operate in this way to avoid undefined level and/or frequency states.
However, the attenuator mode "fixed" together with ALC setting " Auto" (in the RF block - Level menu) allows interruption-free level setting within a limited level range (about 25 dB to 30 dB, indicated by the instrument).
