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Noise Figure measurement using spectrum analyser.

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GVVIN

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One of the method of measuring NF is the gain method using a spectrum analyser. I have a few queries.

1. Will the measurement go wrong if I put internal attenuators.
2. Will spectrum analyser noise figure come in the calculation of NF of DUT.

what is the formula for NF calculation.

NF (DUT) = 10 log10 (measured noise floor with DUT)- 174 -10log10 (RBW)-10log10 (gain of DUT).

Is this correct.
Gain method has limitation like gain should be high and Measured NF should be high > 10 for accurate measurement.

Thanks in advance
Regards
GV
 

1) I dont think If you select internal attenuator before calibration will give you wrong results.
2) In some spectrum analyzer there is a direct facility, they will display NF.
But in some spectrum analyzer you need to measure.

The actual formula for sensitivity calculation is
Sensitivity= -174dBm + NF + 10logBW + required S/N
 

Hi Abhi,

I couldn't understand why you gave me the equation for sensitivity.

regards
GV
 

Here are the articles that may help you. Please check them.

First link:



And second:
 

This is Rhode & Shwartz 's spectrum analyzer's application note.
 

Thanks Abishekh and RF-OM.

I was looking into measurement using a spectrum analyser without NF option and not Y factor method.
I think my equation is right.

I am attaching a application note from Maxim which explains the three methods.

Thank you once again for your time.

Regards
GV
 

This is commercial application notes from Maxim. Unless you need to measure exactly the same Maxim products think again before use this notes. Agilent's application note may be better for your particular application and it is much better technically.
 

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