how to measure LNA noise figure using spectrum analysizer?

Use Y-factor method.
http://cp.literature.agilent.com/lit...5952-3706E.pdf

There are quite a few methods can be used to measure NF- you can find some of the materials from different sites. However, to measure NF using SA, you would require noise source, I am attaching a document from Anritsu, please note: the goal of this note is to get an idea about the NF measurements.

I hope, this helps

For some spectrum analysizers (like Agilent's), to measure NF you need a noise source with the firmware option which supports Y-factor method. There is another solution called "gain method", but it's not suitable for low NF component use. You can google it to find the details.

thanks a lot, guys
:)