Rohde & Schwarz R&S SGS100A - Local Oscillator (LO) Coupling Settings; Phase Coherence

Signal generator settings
R&S
®
SGS100A
94User Manual 1173.9105.02 ─ 13
●
Chapter 11.7, "How to prepare instruments for optimum phase coherence",
on page 167
9.3.1 Phase coherence
Phase coherence of RF signals designates a defined, constant delta phase between
two or more RF carrier signals with the same frequency or a multiple of the frequency.
If two signal generators are coupled via their 10 MHz reference, they are generating
the same frequency but only in the long-term perspective. The instantaneous differen-
tial phase (“delta phase”) of these two RF signals is unstable due to the following:
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Phase noise of the two synthesizers
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“weak” coupling at 10 MHz and a long synthesis chain up to the RF domain
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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 11.7, "How to prepare instruments for optimum phase coherence",
on page 167.
9.3.2 Local oscillator (LO) coupling settings
The LO coupling-related settings are provided in the "Frequency/Phase" dialog.
Access:
► Select "SGMA-GUI > Instrument Name > Frequency/Phase > Local Oscillator (LO)
Coupling".
Local oscillator (LO) coupling