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Noise Figure measurement of the Receiver (Read 4945 times)

wccheng Junior Member Offline Posts: 31	Noise Figure measurement of the Receiver May 24^th, 2004, 12:29am Dear all, I have a simple receiver which is included LNA, downconversion mixer and the VCO. Do I need to add the low pass filter at the IF output for the noise figure measurement? How could I measure it in order to get the correct noise figure result? Best Regards, wccheng ???
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Itay

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Re: Noise Figure measurement of the Receiver
Reply #1 - Dec 24^th, 2004, 12:18pm

Hello,

Sure, you have to add it to the total noise figure. The noise figure of a passive element like filter or attenuator is equal to its loss (only with absolute value). You can measure it with VNA (Vector Network Analyzer) and add it to your measurement. You can calculate the total NF result by using Frii's formula:

NFtot=NF1+NF2-1(G1)+NF3-1/(G1*G2) etc..

Good luck,
Itay

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pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless	Re: Noise Figure measurement of the Receiver Reply #2 - Jan 25^th, 2005, 2:23am Whether you have to put LPF after mixer or not, it depends on IF spectrum purity. If IF output have much undesired spectrum than desired IF spectrum(e.g. local leak which have generally large power leak), an input of NF meter will be over loaded, then you can't measure NF correctly.
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milkdragon

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RF idiot

Posts: 30

Re: Noise Figure measurement of the Receiver
Reply #3 - Sep 1^st, 2005, 5:26pm

You can use the Y-parameter measurement. Simply apply a noise source at the input, turn the noise source on and off to see the difference of the noise floor from the spectrum analyzer, record also the ENR of your noise source, then you can get the NF

LPF is not a must, but your receiver chain has to have high gain, or otherwise it would introduce error

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