R&S FSPN, User Manual

Page: 107 / 555

Common Measurement Settings
R&S
®
FSPN
107 User Manual 1179.4363.02 ─ 01
Remote command:
[SENSe:]FREQuency:CENTer
on page 358
Searching for a signal
The R&S FSPN automatically scans the frequency spectrum for any signals before a
phase noise measurement begins. If it can find a signal on any frequency, it starts a
measurement on that frequency.
The current signal frequency is displayed in the channel bar.
In case you already know the signal frequency, you can also turn off the "Auto Search"
and
define it manually . When you turn off automatic search, the R&S FSPN still verifies
if a signal is present at the frequency you have defined and, if necessary, adjusts the
frequency if the signal is a few Hz off. If you want to skip the signal verification and
measure exactly the frequency you have entered manually, turn off the "Signal Count"
feature. In that case, the R&S
FSPN tunes to the frequency you have entered and
measures its phase noise characteristics, even if no signal is present. Turning off the
frequency counter can improve measurement speed, however.
The measurement starts only if a signal is present within the frequency search limits
that you have defined via the "Auto Search" feature. The search range is defined by a
minimum and maximum value. The maximum frequency range that you can scan
depends on the hardware you are using. Note that a signal must also be within a cer-
tain
level range for it to be detected.
No measurement will be initiated if no signal can be found in the frequency search
range you have defined.
Frequency
f
start
f
stop
Level
p
thr
search
area
Figure 6-2: Basic principle of the signal search feature
During a frequency scan, the R&S FSPN steps through the frequency search range
you have defined in a predefined step size (one step usually covers the full I/Q band-
width).
Signal search is only available for phase noise measurements.
Remote command:
Signal frequency:
[SENSe:]FREQuency:CENTer
on page 358
Mode:
[SENSe:]ADJust:CONFigure:FREQuency:AUTosearch[:STATe]
on page 356
Signal count:
[SENSe:]ADJust:CONFigure:FREQuency:COUNt
on page 356
Lower search limit:
[SENSe:]ADJust:CONFigure:FREQuency:LIMit:LOW
on page 357
Upper search limit:
[SENSe:]ADJust:CONFigure:FREQuency:LIMit:HIGH
on page 357
Frequency