20 | Keysight | M9393A PXIe Performance Vector Signal Analyzer – Data Sheet
Noise Figure Measurement Application
Description
Noise figure
< 10 MHz
Specifications
Supplemental Information
Uncertainty calculator54
See footnote55
10 MHz to 3.6 GHz
Internal and External preamplification
recommended56
Noise source ENR
4 to 6.5 dB
Measurement range
0 to 20 dB
Instrument Uncertainty57
± 0.02 dB
12 to 17 dB
0 to 30 dB
± 0.025 dB
20 to 22 dB
0 to 35 dB
± 0.03 dB
54. The figures given in the table are for the uncertainty added by the X-Series Signal Analyzer instrument only. To compute the total uncertainty for
your noise figure measurement, you need to take into account other factors including: DUT NF, Gain and Match, Instrument NF, Gain Uncertainty
and Match; Noise source ENR uncertainty and Match. The computations can be performed with the uncertainty calculator included with the Noise
Figure Measurement Personality. Go to Mode Setup then select Uncertainty Calculator. Similar calculators are also available on the Keysight web
site; go to http://www.keysight.com/find/nfu.
55. Uncertainty performance of the instrument is nominally the same in this frequency range as in the higher frequency range. However, performance
is not warranted in this range. There is a paucity of available noise sources in this range, and the analyzer has poorer noise figure, leading to higher
uncertainties as computed by the uncertainty calculator.
56. The NF uncertainty calculator can be used to compute the uncertainty. For most DUTs of normal gain, the uncertainty will be quite high without
preamplification.
57. “Instrument Uncertainty” is defined for noise figure analysis as uncertainty due to relative amplitude uncertainties encountered in the analyzer
when making the measurements required for a noise figure computation. The relative amplitude uncertainty depends on, but is not identical to,
the relative display scale fidelity, also known as incremental log fidelity. The uncertainty of the analyzer is multiplied within the computation by an
amount that depends on the Y factor to give the total uncertainty of the noise figure or gain measurement. See Keysight App Note 57-2, literature
number 5952-3706E for details on the use of this specification. Jitter (amplitude variations) will also affect the accuracy of results. The standard
deviation of the measured result decreases by a factor of the square root of the Resolution Bandwidth used and by the square root of the number of
averages. This application uses the 4 MHz Resolution Bandwidth as default because this is the widest bandwidth with uncompromised accuracy.
Description
Specifications
Supplemental Information
Gain
Instrument uncertainty58
DUT gain range = –20 to +40 dB. See note59
< 10 MHz
10 MHz to 3.6 GHz
± 0.10 dB
58. “Instrument Uncertainty” is defined for gain measurements as uncertainty due to relative amplitude uncertainties encountered in the analyzer
when making the measurements required for the gain computation. See Keysight App Note 57-2, literature number 5952-3706E for details on
the use of this specification. Jitter (amplitude variations) will also affect the accuracy of results. The standard deviation of the measured result
decreases by a factor of the square root of the Resolution Bandwidth used and by the square root of the number of averages. This application uses
the 4 MHz Resolution Bandwidth as default since this is the widest bandwidth with uncompromised accuracy. Under difficult conditions (low Y
factors), the instrument uncertainty for gain in high band can dominate the NF uncertainty as well as causing errors in the measurement of gain.
These effects can be predicted with the uncertainty calculator.
59. Uncertainty performance of the instrument is nominally the same in this frequency range as in the higher frequency range. However, performance
is not warranted in this range. There is a paucity of available noise sources in this range, and the analyzer has poorer noise figure, leading to higher
uncertainties as computed by the uncertainty calculator.
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