Keysight Technologies CXA N9000B, Manual

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32 N9069C Noise Figure Measurement Guide
Making Noise Figure Measurements
Making Frequency Converter Measurements
Figure 2-8 shows how filtering makes an LSB measurement, and Figure 2-9
shows a USB downconversion measurement.
Figure 2-8 LSB System Downconverter Measurements
Figure 2-9 USB System Downconverter Measurements
Ideally, choose a high IF for the conversion to separate the USB and LSB
bands, thus simplifying the filter requirements.
The filter needed to make SSB measurement could be part of the DUT, or a
measurement-specific filter must be obtained and applied at the input to the
system downconverter.
Analyzer Input
LSB Input
USB Input
Amplitude
Frequency
F
LO
Band
F
LO
-F
LSB
mixing
Depending on F
lo
, a
downconverter output filter
may be needed to reject
Noise reaching mixer from
the DUT Input filter
LO-IF leakage
F
RF
F
IF
Amplitude
LSB Input USB Input
Frequency
Analyzer Input
F
LO
F
USB
-F
LO
mixing
Band
Depending on F
lo
, a
downconverter output filter
may be needed to reject
LO-IF leakage
Noise reaching System
Downconverter is band
l imited by filtering