W9069A Datasheet, PDF (15/21 Pages) Keysight Technologies – Noise Figure X-Series

15 | Keysight | N9069A & W9069A Noise Figure X-Series Measurement Application - Technical Overview
[1] Analyzer VSWR is characterized to the 95th percentile but not measured and war-
ranted. The VSWR measurement is made on the PNA-X which is traceable. The reverse
isolation of the USAB preamp is high enough that the system VSWR is insignificantly
affected by the analyzer VSWR. So the system VSWR is the warranted VSWR of the USB
preamp.
[2] Analyzer noise figure is computed from the specified DANL using NF = D – (K – L + B),
where D is the DANL (displayed average noise level), K is kTB (–173.98 dBm in a 1 Hz
bandwidth at 290 K), L is 2.51 dB (the effect of log averaging used in DANL verifications),
N is 0.24 dB (the ratio of the noise bandwidth of the RBW filter with which the DANL is
specified to an ideal noise bandwidth), B is ten times the base-10 logarithm of the RBW
(in hertz) in which the DANL is specified. B is 0 dB for the 1 Hz RBW. The actual NF will
vary from the nominal due to frequency response errors. Frequency response errors help
as often as they harm, so NF derived from the DANL is a very good approximation to the
true NF. Any other uncertainties created by deriving the noise figure are small second-
order uncertainties the GUM does not require.
[3] Noise figure for the combination of USB preamp and analyzer is
NF_sys = 10 * Log (F_preamp + (F_analyzer- 1)/G_preamp)
The noise figure and gain of the preamp are specified and warranted. The noise figure of
the analyzer is derived and discussed in [2]. The uncertainty due to the noise figure of the
analyzer is smaller than [2].
[4] “Instrument Uncertainty” is defined for gain measurements as uncertainty due to
relative amplitude uncertainties encountered in the analyzer when making the measure-
ments 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.
[5] Instrument uncertainty for gain is characterized to the 95th percentile above 3.6 GHz.
[6] “Instrument Uncertainty” is defined for noise figure analysis as uncertainty due to
relative amplitude uncertainties encountered in the analyzer when making the mea-
surements 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 computa-
tion 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.
Note: Data subject to change