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Noise Figure Measurements - RF Cafe Forums

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Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement


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

General


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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