Instrument Function
R&S
®
SMB100A
199Operating Manual 1407.0806.32 ─ 21
Exponential AM (Instruments with high frequency options)
Besides the linear amplitude modulation, whereby the signal voltage is proportional to
the modulation signal, instruments equipped with the frequency options (R&S SMB-
B112(L) /-B120(L) /-B140(L)) provide a level-proportional power or amplitude modula-
tion.
In this case, the R&S SMB exponentially distorts the modulation signal, before it is out-
put at the LF CONNECTOR - regardless of the AM Source Int, or Ext . The AM Depth
is then indicated in dB.
Signal Sources for Exponential AM
You can perform exponential AM using either the internal, or an external modulation
signal. However, in contrast to linear AM, the signal at the LF output connector is dis-
torted in any operating mode. AM Source Int+Ext is not available.
5.4.2.1 Amplitude Modulation Settings
To open the "Amplitude Modulation" dialog, select "Modulation > Configure > Ampli-
tude Modulation" or use the MENU key under "Modulation".
In the upper section of the dialog, the modulation source is selected and the modula-
tion switched on. The modulation source can be selected independently for the differ-
ent modulation types and the LF output.
The configuration of the selected external and/or internal modulation source is per-
formed in the lower section of the dialog or in the "LF Output" dialog (internal source
only).
These settings affect all modulations which use the same modulation source.
State
Activates amplitude modulation.
Remote command:
[:SOURce<hw>]:AM:STATe on page 328
AM Source
Selects the source for the AM modulation signal.
"Internal"
Uses the internal LF generator as modulation signal source for AM.
Modulation
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