Concepts and Features
R&S
®
ZNB/ZNBT
225
User Manual 1173.9163.02 ─ 38
ZNBT, e.g. in the in the "More Ratios", "More Wave Quantities", port configuration and
power calibration dialogs.
Reference frequency
To ensure frequency accuracy and frequency stability in a test setup where different
devices represent the signal sources and receivers, it is generally advisable to use a
common reference frequency. Accurate frequencies are particularly important if exter-
nal generators are used for measurements with narrow measurement bandwidths.
A common reference frequency can be established in different ways:
●
Use the analyzer as master device: Set the analyzer to "Internal" frequency refer-
ence ("SYSTEM > SETUP > Freq. Ref. > Internal") and operate all other devices in
external reference mode using the reference clock signal from the REF OUT con-
nector on the analyzer's rear panel.
●
Use another device as master: Set the analyzer to "External" frequency reference
and synchronize it (and all other devices) to the master's reference clock signal,
fed in at the REF IN connector on the analyzer's rear panel.
Fast sweep mode and conditions
In list mode the external generator steps through a predefined list of frequencies or sig-
nal powers. This mode can be used to accelerate the measurements involving external
generators. If "Fast Sweep" is activated in the "External Generators" dialog, the ana-
lyzer compiles a list of the stimulus values (frequencies and powers) in all channels
and transfers it to the generator. The list is automatically updated and re-transferred
whenever the channel settings are changed.
The analyzer uses a trigger handshake mechanism in order to control the generator's
list mode:
●
The generator sends an EXT GEN BLANK signal to pin no. 22 of the USER PORT
connector on the rear panel of the analyzer to show that it is ready to step to the
next frequency or power value in the list.
●
The analyzer transmits an EXT GEN TRG signal at pin no. 21 of the USER PORT
connector in order to switch the generator to the next point in the list. Afterwards
the analyzer waits for the next EXT GEN BLANK signal.
If the USER PORT connection is interrupted during the measurement, the sweep is
halted. It is continued after a "Restart Sweep".
If the number of sweep points exceeds the maximum number of entries in the list
(depending on the generator type), the analyzer must interrupt the sweep in order to
send a new list and complete the stimulus information. This generally slows down the
measurement.
Optional Extensions and Accessories
