R&S FSPN, User Manual

Page: 229 / 555

General Instrument Setup
R&S
®
FSPN
229 User Manual 1179.4363.02 ─ 01
Behavior in case of missing external reference ← Reference Frequency Input
If an external reference is selected but none is available, there are different ways the
instrument can react.
"Show Error
Flag" The error message "External reference missing" is displayed if no
valid external reference signal is available. Additionally, the flag "NO
REF" is displayed to indicate that no synchronization was performed
for the last measurement .
"Switch to
internal refer-
ence" The instrument automatically switches back to the internal reference
if no external reference is available. Note that you must re-activate
the external reference if it becomes available again at a later time.
Remote command:
[SENSe:]ROSCillator:EXTernal:FALLback
on page 482
Tuning Range ← Reference Frequency Input
The tuning range is only available for the variable external reference frequency. It
determines how far the frequency may deviate from the defined level in parts per mil-
lion (10
-6
).
"+/- 0.5 ppm" With this smaller deviation a very narrow fixed loop bandwidth of 0.1
Hz is realized. With this setting the instrument can synchronize to an
external reference signal with a very precise frequency. Due to the
very narrow loop bandwidth, unwanted noise or spurious components
on the external reference input signal are strongly attenuated. Fur-
thermore, the loop requires about 30 seconds to reach a locked state.
During this locking process, "NO REF" is displayed in the status bar.
"+/- 6 ppm" The larger deviation allows the instrument to synchronize to less pre-
cise external reference input signals.
Remote command:
[SENSe:]ROSCillator:TRANge
on page 482
Frequency ← Reference Frequency Input
Defines the external reference frequency to be used (for variable connectors only).
Loop Bandwidth ← Reference Frequency Input
Defines the speed of internal synchronization with the reference frequency. The setting
requires a compromise between performance and increasing phase noise.
For a variable external reference frequency with a narrow tuning range (+/- 0.5 ppm),
the loop bandwidth is fixed to 0.1 Hz and cannot be changed.
Remote command:
[SENSe:]ROSCillator:LBWidth
on page 479
Reference Frequency Output
A reference frequency can be provided by the R&S FSPN to other devices that are
connected to this instrument. If activated, the reference signal is output to the corre-
sponding connector.
"Output 100 MHz"
Provides a 100 MHz reference signal to the REF OUTPUT 100 MHz
connector.
Reference Frequency Settings