Rohde & Schwarz SMU200A - Typical Applications

Instrument Function
R&S
®
SMU200A
207Operating Manual 1007.9845.32 ─ 15
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.
5.5.5.2 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.
●
Generation of 2xN MIMO signal with one R&S Signal Generator, working in Coupled
A->B mode.
RF Signal and Analog Modulations - RF Block