R&S 1322.8003K06, Руководство пользователя

Страница: 109 / 555

Common Measurement Settings
R&S
®
FSPN
109 User Manual 1179.4363.02 ─ 01
●
Very low signal levels can be measured by selecting the appropriate level setting
and applying the low pass filter.
Low signal frequencies ← Measuring low frequency and low level signals
The R&S FSPN provides a low pass filter that suppresses the DC offset of the I/Q
mixer to measure signal frequencies below 1 MHz. Applying the filter results in a better
sensitivity.
When you are measuring such signals, turn on the filter ("State"), and define its "Cutoff
Frequency". The cutoff frequency should be the same as the signal frequency. For
example, the cutoff frequency to measure a signal frequency of 100
Hz should also be
100 Hz.
Measuring low frequencies and levels is available for phase noise measurements on
continuous wave signals.
Note that using the filter has several effects.
●
The automatic search for a signal is not supported. Define the signal frequency
manually instead.
●
A signal count is not possible.
●
The stop offset is limited to 30 % of the carrier signal frequency.
For measurements on frequencies below 10 MHz, you must use DC coupling (inde-
pendent of the low pass filter).
Remote command:
Filter state:
[SENSe:]FILTer:LPASs[:STATe]
on page 358
Cutoff frequency:
[SENSe:]FILTer:LPASs:FREQuency:MANual
on page 357
Low signal levels ← Measuring low frequency and low level signals
The R&S FSPN supports different modes to measure signals with different levels.
Depending on the measurement, select the appropriate "Level Setting".
●
"High": The R&S FSPN works like a traditional phase noise tester with zero IF and
is therefore limited in the sensitivity.
●
"Low": The R&S FSPN uses an IF of 15 MHz. Therefore, the DC offset of the I/Q
mixers does not limit the sensitivity. It is recommended to use this level setting for
signal levels below -20
dBm.
For very low signal levels (below approximately -40 dBm), the broadband noise in
the demodulator becomes an issue and disables the measurement. To measure
such signals, apply the
low pass filter , because it reduces the noise bandwidth.
The nominal improvement of the sensitivity is 10 dB for 10 MHz, 20 dB for 1 MHz
cutoff frequency.
Note that using the filter has several effects.
●
The automatic search for a signal is not supported. Define the signal frequency
manually instead.
●
A signal count is not possible.
●
The stop offset is limited to 30 % of the carrier signal frequency.
Remote command:
Filter state:
[SENSe:]FILTer:LPASs[:STATe]
on page 358
Cutoff frequency:
[SENSe:]FILTer:LPASs:FREQuency:MANual
on page 357
Level setting:
[SENSe:]POWer:RLEVel:MODE
on page 360
Frequency