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NRT
CONFig Menu
1080.9506.02
2.19
E-8
The table below shows the bandwidths to be set for some common waveforms.
Table 2-1
Setting the video bandwidths for the PEP, CF, and CCDF measurement functions
Waveform
Video bandwidth NRT (f)*
NRT-Z43/44
AM mod.
frequency
≤
1
kHz
4 kHz (0)
AM mod.
frequency
≤
50 kHz
200 kHz (1)
CW burst
burst width
≥
150
µs
4 kHz (0)
CW burst
burst width
≥
3 µs
200 kHz (1)
CW burst
burst width
≥
200 ns
FULL (2)
π
/4 DQPSK
symbol rate
≤
24 k/s
200 kHz (1)
π
/4 DQPSK
symbol rate
≤
200 k/s
FULL (2)
CDMA/W-CDMA
chip rate
≤
8.2 M/s
FULL (2) **
DAB/DVB-T
---------------
FULL (2) **
*) f:
Index for setting the band width via IEC-bus with the command
:SENSe<n>:BANDwidth:VIDeo:FNUMber <f>
**)
To increase the accuracy of spread spectrum signal measurements, the name of the used standard
should be reported to the NRT; see Section 2.4.3.
2.3.1.2 Crest
Factor
The crest factor CF is the level difference between the PEP value and the average power in dB:
CF 10 dB log
PEP
AVG
=
×
The crest factor provides information about the dynamic range of transmitters, eg with CDMA signals,
for which values up to 10 dB are possible. This measurement is only possible with sensors of type NRT-
Z and requires selection of a suitable video bandwidth. The available bandwidths are sensor-dependent
and indicated in the menu in plain text as soon as the CF setting has been acknowledged in the next
higher menu. The bandwidths shown in the figure below – 4 kHz, 200 kHz, and
"FULL"
– can be set with
sensors NRT-Z43/44.
"FULL"
means that the maximum bandwidth of the sensor, i.e. approx. 4 MHz, is
used.
CONFig - ENV KEY - CF -
VID.BW:
The video bandwidth set in this menu overwrites the settings made in the menus
CF, AV.BRST - AUTO
and
CCDF
.
The video bandwidth should be selected as narrow as possible for the measurement task at hand, since
in this way the noise superimposed on the rectified signal can be kept low. Low noise causes less varia-
tions in indication and allows measurement of the crest factor at low power. Reducing the bandwidth too
much, however, may lead to an unwanted distortion of the envelope, see Fig. 2-4.
Table 2-1 shows the
appropriate setting for some waveforms.
IEC/IEEE command:
:SENSe<n>:FUNCtion[:ON] "POWer:CFACtor"
:SENSe<n>:BANDwidth:VIDeo:FNUMber <f>
<f>
: see Table 2-1, the preset value depends on the sensor used.
深圳德标仪器
135-1095-0799
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