Keysight Technologies N9040B UXA Manual page 32

Making Noise Figure Measurements
Making Frequency Converter Measurements
Figure 2-8
shows a USB downconversion measurement.
Figure 2-8 LSB System Downconverter Measurements
Amplitude
Figure 2-9 USB System Downconverter Measurements
Amplitude
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.
32
shows how filtering makes an LSB measurement, and
F
IF
F -F
LO LSB
mixing
Noise reaching mixer from
the DUT Input filter
Analyzer Input
Band
F -F
USB LO
mixing
Depending on F , a
lo
downconverter output filter
may be needed to reject
LO-IF leakage
Analyzer Input
Band
F
RF
F
LO
LSB Input
F
LO
LSB Input USB Input
N9069C Noise Figure Measurement Guide
Figure 2-9
Depending on F , a
lo
downconverter output filter
may be needed to reject
LO-IF leakage
Frequency
USB Input
Noise reaching System
Downconverter is band
limited by filtering
Frequency