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Noise figure measurements - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.


Seth
Post subject: Noise figure measurements Posted: Thu Mar 19, 2009 2:56 am

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Joined: Sun Nov 02, 2008 10:16 pm
Posts: 1
My question is on sub 1 dB noise figure measurements. Although I am using a low ENR source and an industry standard noise figure analyzer, I get the impression that the noise figure readings are consistently a little on the high side (0.2-0.3 dB higher) on the low noise amplifiers that I am measuring. Is there an accurate way to cross check the measurements that I am making? The instrument noise figure at the frequency of measurement is about 8.5 dB. Does one have to use a preamplifier to get more accurate results?


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nubbage
Post subject: Re: Noise figure measurementsPosted: Sat Mar 21, 2009 6:32 am

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Joined: Fri Feb 17, 2006 12:07 pm
Posts: 218
Location: London UK
Hi Seth
I had a look at graph 6.1 of Agilent's App Note 57-2 "Noise Figure Measurement Accuracy". It estimates around 0.3dB error when using an analyzer with an 8.5dB NF.
You might expect an error of around 0.2dB if you place a good 2dB NF pre-amp in front of the analyzer.

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IR
Post subject: Re: Noise figure measurementsPosted: Sat Mar 21, 2009 3:55 pm

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Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
You can do the following:

1. Compare the measurements between different DUT's and get a insight on the error magnitude.
2. Use another unit of the same Noise Figure Analyzer which you currently use and see if you get the same size of error - then most probably it is a measurement error of the Analyzer.
3. Better not to use another preamplifier, because then you add another error factors to your measurement setup (Gain and NF).

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