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R&S
FS-K30
Measurements & Settings
Graphic
Settings
Software Manual 1300.6637.42 - 03
85
2.8.8 Frequency-converting Measurement
The frequency-converting measurement is used for DUTs that have an output frequency
that differs from the input frequency, e.g. mixers and satellite converters. The converting
measurement allows many variations, which differ from each other in two criteria:
I
Fixed local oscillator frequency or fixed intermediate frequency with tracking LO
frequency
I
Rejection of image frequency (SSB, DSB)
2.8.8.1 Fixed LO and Fixed IF measurements
If a converting DUT with a fixed intermediate frequency is to be measured, R&S FS-K30
must be configured to vary the associated local oscillator in its frequency. This generator
is controlled via the IEC bus. The required settings are made in the
Measurement
Settings
view. One of the following settings for the
Mode
parameter in the
Frequency
Settings
view must be selected in the case of the fixed intermediate frequency
measurements:
fix IF LO=RF+IF
fix IF LO=abs(RF–IF)
For measurements of a DUT with fixed LO frequency, control of an external signal
generator by R&S FS-K30 is not absolutely necessary. One of the following settings for
the
Mode
parameter in the
Frequency Settings
view must be selected in the case of
the fixed local oscillator frequency measurements:
fix LO IF=RF+LO
fix LO IF=abs(RF–LO
2.8.8.2 Image-frequency Rejection (SSB, DSB)
Frequency-converting DUTs often do not only convert the desired input frequency but
also the image frequency. A broadband noise source offers noise to the DUT not only
at the input frequency but also at the image frequency. If the noise power at the IF gate
is measured, the origin of the noise can no longer be determined. It may have been
converted both from the input and from the image frequency range.
Example: IF = 100 MHz; LO-Freq. = 500 MHz; input frequency: 400 MHz; image
frequency: 600 MHz
freq.
LO
RF
IF
Image
If a DUT, which equally converts the useful signal and the image to the IF frequency, is
measured using the conventional Y-factor method or with the setting
2nd stage