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Problem with measuring LNA noise figure

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thiagoyk

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I'm trying to measure a LNA Noise Figure.
I'm using the 8970B with the Special Function 1.5
The LNA works at 2.2 to 2.4 Ghz.
I checked 100 times all the connections and configurations, and I always get 0.3dB.
I know that this LNA must have 0.7 dB of NF and 13 dB Gain.
Does someone had a problem like this?
 

sergio mariotti

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Re: NF measure problem

thiagoyk said:
I'm trying to measure a LNA Noise Figure.
I'm using the 8970B with the Special Function 1.5
The LNA works at 2.2 to 2.4 Ghz.
I checked 100 times all the connections and configurations, and I always get 0.3dB.
I know that this LNA must have 0.7 dB of NF and 13 dB Gain.
Does someone had a problem like this?
1) If you use 1.5SF it'means you also use 8971; is it right?
2) Try DSB measurement also.
3) check LO spurious / noise.
4) place a ferrite isolator in front of the converter.
5) after calibration, try to measure NF and gain af a small attenuator (i.e. 3dB).
6) If all previously points are OK , consider the following:
7) I've experienced a MiniCircuit Amplifier rated to have NF<1.5 that actually have a measured NF=0.9dB. Does you LNA has NF=0.7 dB or NF<0.7dB ? check critically the data sheet.
8) ENR Uncertainty. Unfotunately, the only way to be sure about the ENR value, is the comparition with another Noise Source, this may be the most expensive way.
 

flyhigh

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Re: NF measure problem

Hi,

besides the measureing the noise figure, you should chech return loss (S11) of your LNA. Due to the nature of the noise mesurements, if input return loss is poor, it will fake the noise figure meter and you will be getting better noise figure and higher gain than it realy is

flyhigh
 

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