86 N9069C Noise Figure Measurement Guide
Measurement Related Tasks and Concepts
Calculating the Noise Power into Different Stages of the Noise Figure Measurement
System
Calculating the Noise Figure for Noise Power Calculation
To calculate the noise power using
, you need to calculate the
noise figure of a part of the test system. This section gives an example of
calculating the noise figure of the combination of DUT, USB Preamp, internal
attenuator, and internal preamp. It can be seen as 4 stage systems, so the total
noise figure F can be calculated using
, in which the F and G are
all in linear terms.
Equation 3-3
and are the noise figure and Gain of the DUT.
and are the noise figure and Gain of the USB Preamp. You can get a
rough values from the Keysight USB Preamplifers Technical Overview,
5991-4246EN.
and are the noise figure and Gain of the internal attenuator. The noise
figure of the internal attenuator is equal to its attenuation.
is the noise figure of the internal preamp. You can get the rough values from
the specification guide of the signal analyzer. Note that the noise figure values
from the specification guide is the noise figure of the instrument with the
internal preamp turned on. As the internal preamp has high gain, this value is
taken as the noise figure of the internal preamp here.
Gain
dB
DUTGain USBPreampGain InternalPreampGain Internal Attenuation
–
+
+
=
F
F
1
F
2
1
–
G
1
----------
F
3
1
–
G
1
G
2
----------
F
4
1
–
G
1
G
2
G
3
--------------
+
+
+
=
F
1
G
1
F
2
G
2
F
3
G
3
F
4
Summary of Contents for CXA N9000B
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