Rohde & Schwarz SMBV100A - LO Coupling Settings; Typical Applications

Instrument Function
R&S
®
SMBV100A
218Operating Manual 1176.8016.02 ─ 17
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 synthe-
sizer, i.e. a common local oscillator (LO) signal, for all RF carriers. Only if this LO sig-
nal (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 beamformed signal.
●
Generation of a beamformed signal with two instruments, working in External
mode.
5.5.5.3 LO Coupling Settings
To open the "LO Coupling" dialog, 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 5.5.2.3, "RF Frequency Dialog", on page 210
●
Chapter 5.5.3.1, "Phase Settings", on page 213
●
Chapter 5.5.4.1, "Reference Oscillator Settings", on page 215
RF Block