Rohde & Schwarz SMBV100A, Руководство по эксплуатации

Страница: 344 / 911

Instrument Function
R&S
®
SMBV100A
329 Operating Manual 1176.8016.02 ─ 17
External clock reference
An external clock is always supplied via the CLOCK connector. When the external
clock reference is selected, the internal clock is synchronized to it. The table bellow
gives an overview of the connectors the internal clocks are output at.
Connector Location Clock Mode
CLOCK OUT rear panel Symbol clock
The active edge of the external clock signal on the CLOCK input is selectable (menu
"Setup > System > Global Trigger/Clock/External Inputs"). Internally the rising edge is
always taken as the active edge. The active rising edge of the internal clocks is there-
fore synchronized with either the rising or the falling edge of the external clock refer-
ence. A symbol clock can be supplied externally or, if internally generated or externally
asynchronous data is being fed in, a multiple of a symbol clock can be supplied.
In order for the clock synthesizer on the R&S SMBV to be synchronized correctly, the
external clock reference must first be applied and the correct symbol rate must then be
set. Until this has been done the external clock source must not be selected ("Clock
Source External").
The symbol rate set must not deviate from the symbol rate of the external signal by
more than 2% (see also data sheet).
5.9.2.4 Synchronous Signal Generation
Different simulation schemes such as MIMO for instance require the generation of two
or more very precise synchronized signals in the baseband and the RF domain.
Two or more instruments are denoted as “perfectly synchronized” if the following crite-
ria are fulfilled:
●
The frequency and the phase of the RF carriers are equal.
●
The RF levels are equal
●
The modulation signals have equal timing, i.e. the symbol rate and the signal gen-
eration start determined by the triggering are equal. The contents of the signal,
however, may be different, as it is for instance in a MIMO system.
In the R&S SMBV, the first two requirements are fulfilled by adjusting the parameters
"Baseband Phase Offset" and "RF Level". A special synchronization mode is provided
to meet the third requirement, i.e. to enable several R&S
SMBV to generate a simulta-
neous and synchronous signal.
Synchronization mode is an instrument's configuration in which one of the instruments
is used as a master and the other(s) are slave(s). The master instrument supplies the
slave instrument(s) with its system and reference clock as well as with its trigger signal.
Baseband Signal - Baseband Block