Rohde & Schwarz SMBV100A - Automatic Level Control - ALC

Instrument Function
R&S
®
SMBV100A
226Operating Manual 1176.8016.02 ─ 17
Display Level as Voltage of EMF - RF Level
Activates display of the signal level as voltage of the EMF (no-load voltage). If this set-
ting is deactivated, the level is displayed as a voltage over a 50 Ohm load.
Note: This setting is not affected by an instrument preset (PRESET key), *RST) or the
"Save/Recall" function. Only the Chapter 5.2.3.20, "Factory Preset", on page 154
resets the setting.
Remote command:
[:SOURce<hw>]:POWer:EMF:STATe on page 788
5.5.7 Automatic Level Control - ALC
Your signal generator is equipped with an automatic level control unit to obtain best RF
level accuracy.
Automatic Level Control (ALC) is an adaptive control system to stabilize the RF output
level. It continuously monitors the current level and adjusts it to keep a steady state
over temperature and time.
ALC is active in almost all applications by default. However, some operating modes
exclude ALC, as the control loop would detect incorrect values and result in level devi-
ations. These are:
●
Pulse modulation
●
I/Q modulation
Also note that ALC may detect incorrect values in multi-transmitter test setups. If mul-
tiple generators are coupled, reverse power may affect the ALC readings. Based on
incorrect values, ALC would have an impact on the signal to intermodulation ratio.
ALC States
The following description basically explains the ALC states and their principle of opera-
tion. In particular ALC OFF (Sample & Hold) gives an overview on the function in
terms of the equipment of the generator.
The R&S SMBV offers the ALC states:
●
AUTO
automatically adjusts the output level to the operating conditions.
●
On
enables ALC permanently, regardless of the currently selected mode.
●
Off
deactivates ALC.
To maintain a defined output level in Off mode, you can choose either Sample &
Hold (S&H) status or Table.
– "S&H"
activates ALC briefly when frequency or level settings change.
– "Table"
uses predefined values from a table to adjust the level at changes.
RF Block