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Measurements >> RF Measurements >> Measure NF of low-IF mixer
https://designers-guide.org/forum/YaBB.pl?num=1253671020

Message started by aaron_do on Sep 22^nd, 2009, 6:57pm

Title: Measure NF of low-IF mixer
Post by aaron_do on Sep 22^nd, 2009, 6:57pm

Hi all,

I want to measure the NF of a downconversion mixer with an IF of around 100 kHz. Can anybody reccommend equipment to do this? Currently I am using an ESA spectrum analyzer with built in noise personality (it uses the Y-factor method), but the analyzer is not designed to be used below 10 MHz (although it will output data). So i'm worried that the measurement results are far off.

Another method I thought of using is the gain method where I don't need a noise source. Is this method considered accurate for my application. The DUT gain is around 30 dB and the RF frequency is 2.4 GHz.

thanks,
Aaron

Title: Re: Measure NF of low-IF mixer
Post by ACWWong on Sep 23^rd, 2009, 5:48am

I think more important than the gain is the NF you are expecting. A very low noise figure would be more suspectable to measurement errors using simple C/N NF calculation.

Title: Re: Measure NF of low-IF mixer
Post by aaron_do on Sep 23^rd, 2009, 8:26am

I expect an NF of around 6 dB. I figured that the main consideration is the output noise versus the noise floor of the spectrum analyzer...

thanks,
Aaron

Title: Re: Measure NF of low-IF mixer
Post by ACWWong on Sep 23^rd, 2009, 8:51am

Yes based on these numbers, it should be fine to use a spectrum analyser and C/N method.
Analyser noise floor is easily de-embedded... e.g. noise floor 6dB below DUT noise contibutes 1dB to the measured noise, 10dB below contibutes 0.4dB etc.
A post amp might help to get the DUT noise above analyser noise floor if its a problem.