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Mixer Noise Figure
Concerns and
Measurements
Ed Cantrell
Oct. 1984
RF &.. Microwave
Measurement
Symposium
and
Exhibition
rhO- HEWLETT
~~ PACKARD
www.HPARCHIVE.com
Why Is Noise Important?
Receiver
System
Small Imperfect Signal Noisier
Signal Device
or
System
Noise limits the detection of weak signals. As a signal is passed through a device or system, noise is added, thus
degrading the signal to noise ratio. Noise figure is a measure of this degradation.
1
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Noise Figure Definition
Total Output Noise Power
F
Output Noise Power Due To Input Noise @ 290K
kTsB ~ No Na + kTsBG
r-----O_---4!Na~>------o=
..> V"
.. Zs @ Ts
..:
-==-
Na + kTsBG
F
kTsBG Ts 290K
FdB 10 log F
Noise figure is a measure of signal to noise ratio degradation of any device or system that has at least one input
and one output. It applies to systems as well as components of the system.
2
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Why Is Mixer Noise Figure Important?