General instrument setup
R&S
®
FSVA3000/ R&S
®
FSV3000
725
User Manual 1178.8520.02 ─ 08
mand for the required input type (see
"Input-specific frequency correction"
Otherwise the correction may seem to fail because it was defined for a different input
type than the one being used.
Touchstone (.snp) files
Touchstone (
.snp
) files contain data to characterize a measurement setup in respect
to the gain and phase error over frequency. Such files are generated by network ana-
lyzers, for example. The R&S
FSV/A can use such files to compensate for any gain or
phase errors between the DUT and the connection from the DUT to the instrument.
Touchstone files can be defined for a varying number of input and output ports. The
total number of ports configured in the file is indicated by the file extension; the "n"
in
.snp
is merely a placeholder. Thus, a file for a cable with one input and one output
is referred to as an S2P file. A file for a switch with one input and 3 outputs is referred
to as an S4P file etc.
Transducer vs filter function
Touchstone files are handled similarly to transducer files by the R&S
FSV/A. However,
while a transducer adapts the frequency values by a fixed factor, Touchstone files act
as a filter on I/Q input data. For common frequency sweeps, the effects of transducers
and Touchstone files are the same.
.fres files
Additional frequency response correction files in
.fres
format allow you to correct
effects from components for which no Touchstone files are available.
Files in
.fres
format correspond to an S1P file. They contain exactly three values for
each frequency:
●
The frequency
●
The magnitude correction value
●
The phase correction value
Instead of the magnitude and phase correction values, the I and Q values can be provi-
ded.
These values are applied to the input data. If the file contains any other data, it cannot
be loaded.
For
.fres
files, magnitude and phase correction can be activated separately.
Group delay compensation
The phase correction values can be used to compensate for a group delay. However,
to calculate the correction correctly, the distance between two values must not be too
large. Thus, the application requires a minimum number of values in the correction file.
Define at least enough values so the following equation is true:
Group_delay * Frequency_Spacing * 360 < 180
Frequency response correction (R&S
FSV/A-K544)
