Brief Description of Vector Signal Analysis
R&S
®
FSV-K70
14
Operating Manual 1176.7578.02 ─ 09
Usage of the optional hardware can be deactivated, if necessary, for example to
reduce possible spurious effects.
2.2.2.1
Restrictions
The optional bandwidth extension R&S
FSV-B160 can not be activated if any of the fol-
lowing conditions apply:
●
R&S FSV firmware versions previous to 2.0
●
R&S FSV models 1307.9002Kx
●
For R&S FSV models 1321.3008K13/30/39/40: For center frequencies larger than
7
GHz
●
For sample rates < 32
MHz
●
With any trigger except for an external trigger
2.2.3 Demodulation Bandwidth (Measurement Bandwidth)
Some modulation systems do not use a receive filter. In these cases special care
should be taken that no interference or adjacent channels occur within the demodula-
tion bandwidth. The "Capture Oversampling" parameter should be set to a low value
(see
Typical communication systems demand special receive or measurement filters (e.g.
root-raised cosine receive filter or EDGE measurement filter).
If no such filtering is performed, care should be taken that neither interfering signals
nor adjacent channels fall within the demodulation bandwidth.
2.2.4 Modulation and Demodulation Filters
Sample points are required for demodulation in the analyzer, where only information of
the current symbol and none of neighbouring symbols is present (symbol points).
These points are also called ISI-free points (ISI = intersymbol interference). If the trans-
mitter does not provide an ISI-free signal after the transmit filter (
TX filter
), this condi-
tion can be fulfilled by signal-specific filtering of the analyzer input signal (
receive filter
or
Rx filter
). If an RRC (root-raised cosine) filter is used in the transmitter, an RRC fil-
ter is also required in the analyzer to obtain ISI-free points.
In many PSK systems, RRC filters are used as transmit, ISI and measurement filters.
To determine the I/Q modulation error, the measurement signal must be compared
with the corresponding ideal signal. For this purpose a
reference filter
is required
which is calculated by the analyzer by convolving the coefficient of the transmit filter
(
Tx filter
) and the
meas filter
If unfiltered signals have to be measured as well (e.g. to determine nonlinear signal
distortions), no measurement filter is switched into the signal path and the
reference
filter
is identical to the
Transmit filter
Filters and Bandwidths During Signal Processing
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