Signal Generator Settings
R&S
®
SGS100A
83User Manual 1173.9105.02 ─ 12
If two signal generators are coupled via their 10 MHz reference, they are generating
exactly the same frequency but only in the long-term perspective. Having a closer look
into the instantaneous differential phase (“delta phase”) of these two RF signals, this is
unstable due to:
●
Phase noise of the two synthesizers
●
“weak” coupling at 10 MHz and a long synthesis chain up to the RF domain
●
Temperature differences, which cause slightly different phase drift for the different
synthesizers
Most critical for a stable delta phase is the thermal RF phase fluctuation between multi-
ple RF synthesizers. These fluctuations can be minimized by using a common synthe-
sizer (common local oscillator (LO) signal) for all RF carriers.
See also Chapter 9.7, "How to Connect and Configure Instruments for Optimum Phase
Coherence", on page 154.
7.3.2 Local Oscillator (LO) Coupling Settings
The LO coupling-related settings are provided in the "Frequency/Phase" dialog.
► To access this dialog, select "SGMA-GUI > Instrument Name > Frequency/Phase >
Local Oscillator (LO) Coupling".
Source
Selects the source of the local oscillator signal.
"Int"
The instrument uses the built-in local oscillator.
Local Oscillator (LO) Coupling
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