Instrument Function
R&S
®
SMBV100A
162Operating Manual 1407.6062.32 ─ 08
If two signal generators are coupled via their 10 MHz reference, they are generating
exactly the same frequency but only from the long term perspective. Having a closer look
into the instantaneous differential phase (“delta phase”) of these two RF signals, this is
quite instable 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 a change of the effective electrical length of
some synthesizer components
Most critical for a stable delta phase is the thermal RF phase drift between multiple RF
synthesizers. This drift can be minimized down to 0.1° by use of a common synthesizer,
i.e. a common local oscillator (LO) signal, for all RF carriers. Only if this LO signal (which
is internally used for upconverting the baseband signal to the RF) is the same for all
carriers, a stable phase between the RF signals can be achieved.
5.4.5.2 Typical Applications
The LO Coupling function can be used to generate a MxN MIMO signal.
●
Generation of 2xN MIMO signal with two R&S Signal Generators, working in External
mode.
5.4.5.3 LO Coupling Menu
To open the "LO Coupling" menu, select "RF/A Mod > Configure > LO Coupling" or use
the MENU key under "RF/A Mod".
The menu is available only for instruments equipped with the option R&S SMBV-B90.
This option enables phase coherent RF outputs of two or more RF paths.
The local oscillator coupling is set in the lower area of the group menu "Frequency/
Phase". The menu is used to select the mode of the LO coupling and the state of the local
oscillator output.
For more information about the upper areas, see:
● chapter 5.4.2.3, "RF Frequency Dialog", on page 157
● chapter 5.4.3.1, "Phase Settings", on page 159
● chapter 5.4.4.1, "Reference Oscillator Dialog", on page 159
RF Signal and Analog Modulations - RF Block
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