R&S FSW Series, Руководство пользователя

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Measurements and Results
R&S
®
FSW
160 User Manual 1173.9411.02 ─ 43
The "Sweep Time" can be defined using the softkey in the "Ch Power" menu or in the
"Sweep" configuration dialog box (see
"Sweep Time" on page 173).
Frequency Span
The frequency span must cover at least the channels to be measured plus a measure-
ment margin of approximately 10 %.
If the frequency span is large in comparison to the channel bandwidth (or the adjacent-
channel bandwidths) being analyzed, only a few points on the trace are available per
channel. The calculated waveform for the used channel filter is less accurate, which
has a negative effect on the measurement accuracy. It is therefore strongly recommen-
ded that you consider the described formulas when you select the frequency span.
The frequency span for the defined channel settings can be optimized. Use the "Adjust
Settings" function in the "Ch Power" menu or the "General Settings" tab of the "ACLR
Setup" dialog box (see
"Optimized Settings (Adjust Settings)" on page 173). You can
set the frequency span manually in the "Frequency" configuration dialog box.
(See Chapter 8.3.4, "How To Define the Frequency Range" , on page 447.)
For channel power measurements the "Adjust Settings" function sets the frequency
span as follows:
"(No. of transmission channels – 1) x transmission channel s 2 x transmission
channel ban measurement margin"
For adjacent-channel power measurements, the "Adjust Settings" function sets the fre-
quency span as a function of the following parameters:
●
Number of transmission channels
●
Transmission channel spacing
●
Adjacent-channel spacing
●
Bandwidth of one of adjacent-channels ADJ, ALT1 or ALT2, whichever is furthest
away from the transmission channels
"(No. of transmission channels – 1) * (transmission channel s 2) * (adjacent-
channel s adjacent-channel bandwidth) + measurement margin"
The measurement margin is approximately 10 % of the value obtained by adding the
channel spacing and the channel bandwidth.
Resolution Bandwidth (RBW)
It is important to suppress spectral components outside the channel to be measured,
especially of the adjacent channels. At the same time, you expect an acceptable mea-
surement speed. To fulfill both these requirements, the appropriate resolution band-
width is essential. As a general approach, set the resolution bandwidth to values
between 1
% and 4 % of the channel bandwidth.
If the spectrum within the channel to be measured and the spectrum around the chan-
nel has a flat characteristic, you can select a larger resolution bandwidth. In the stan-
dard setting, e.g. for standard IS95A REV at an adjacent channel bandwidth of 30
kHz,
a resolution bandwidth of 30 kHz is used. This yields correct results since the spectrum
near the adjacent channels normally has a constant level.
Channel Power and Adjacent-Channel Power (ACLR) Measurement