Configuring the Signal in the RF Domain
R&S
®
SMW200A
449User Manual 1175.6632.02 ─ 16
The internal LO signal is output at the LO OUT connector, and an external signal is fed
in at the LO IN connector, see "To find the physical Location of the LO In/Out connec-
tors" on page 454.
You can couple the LO signal as follows:
●
"A Internal & A -> B Coupled"
The R&S SMW uses the internal oscillator signal of path A also in path B.
The reference frequency settings in path B have no effect and are thus disabled for
editing.
●
"A External & A -> B Coupled"
The R&S SMW receives an external oscillator signal and uses this signal in both
paths.
The reference frequency settings in both paths have no effect and are thus dis-
abled for editing.
Note: As the instrument cannot verify the frequency of the oscillator signal that is
fed in, it is essential that this signal has exactly the frequency shown in the settings
dialog, see LO OUT Frequency.
Similarly, you can couple the signals of cascaded instruments as shown in "To config-
ure LO coupling with cascaded instruments to achieve phase coherence"
on page 454.
Level adjustment
The level range of the LO input and LO output signal is 10 dBm ±3 dB, as specified in
the data sheet of the R&S SMW.
The instrument uses the default settings to adjust its internal level, which is sufficiently
accurate for most applications.
But consider that the oscillator signal level at LO IN should be stable, with minimized
phase noise and interferences. The fed in signal is directly used in the instrument, and
thus affects the instrument performance. We recommend that you keep the (sub-)har-
monics below -20 dBc, and the level stable within ±0.1 dB over time and temperature
However, if you need optimum performance, or if you have long interconnections
between LO OUT and LO IN, we recommend that you adjust the LO level at the cur-
rent frequency. Using this function, the instrument readjusts the internal signal levels to
optimum.
The adjustment may take a few milli seconds.
Local Oscillator Coupling
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