Instrument Functions
R&S
®
FSVA/FSV
520Operating Manual 1176.7510.02 ─ 09
The voltage U0 at the output of the operational amplifier can be set in the range –2.0 to
+2.0 V An open-circuit voltage Vbias of –0.5 to +0.5 V is obtained accordingly at the
output of the voltage divider. A short-circuit current of Ishort = V0 / 200 Ω = 10 mA to +
10 mA is obtained for a short circuit at the output of the voltage divider. For using bias-
ing it is not important to know exactly the current flowing through the diode since the
conversion loss must be set to minimum with the frequency. It therefore makes no dif-
ference whether the setting is performed by an open-circuit voltage or by a short-circuit
current. A DC return path is ensured via the 66 Ω resistor, which is an advantage in
some mixers.
3.8.1.3 Conversion Loss Tables
Conversion loss tables consist of value pairs that describe the correction values for
conversion loss at certain frequencies. Correction values for frequencies between the
reference values are obtained by interpolation. Linear interpolation is performed if the
table contains only two values. If it contains more than two reference values, spline
interpolation is carried out. Outside the frequency range covered by the table the con-
version loss is assumed to be the same (see Figure 3-41) as that for the first and last
reference value.
Figure 3-41: Conversion loss outside the band's frequency range
Predefined conversion loss tables are often provided with the external mixer and can
be imported to the R&S FSVA/FSV. Alternatively, you can define your own conversion
loss tables. Conversion loss tables are configured and managed in the "Conversion
Loss Table Setup" tab of the "External Mixer Configuration" dialog box (see "Conver-
sion Loss Table Setup" on page 528).
The conversion loss table to be used for a particular range is defined in the "External
Mixer Configuration" dialog box. All tables stored on the instrument in the
C:\r_s\instr\user\cvl\ directory are offered for selection. A validation check is
then performed on the selected table to ensure that it complies with the settings. In
particular, the following is checked:
Instrument Functions – External Mixer (Option R&S FSV-B21)
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