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Measurements >> RF Measurements >> Input Referred Noise
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Message started by aaron_do on Jul 10^th, 2007, 8:33pm

Title: Input Referred Noise
Post by aaron_do on Jul 10^th, 2007, 8:33pm

Hi all,

are there any instruments to directly measure Input Referred Noise?

thanks,
Aaron

Title: Re: Input Referred Noise
Post by greenlinux on Sep 4^th, 2007, 11:21am

I suspect the best you can hope for is to measure the output noise and divide by the gain of your system. Otherwise you may have a problem with the sensitivity of your noise meter, or the internal noise of the meter being significant cf. the noise you wish to measure.

If you wish, you may consider a 2 port measurement system that has the same structure as a network analyser but measures small signal gain and output noise. It would then divide the latter by the former to provide the input noise. if you did some cool jiggery pokery it may be possible to do this in discrete frequency blocks it would then be possible to plot the data from each frequency segment on a graph and get something approximating a curve of input referred Noise voltage (or current) vs. Frequency. Of course you would have to do some maths on your raw data to produce a Y - axis that reads volts(or amps) per root Hz (or volts^2 (or amps^2)/Hz if you prefer).

I submit this as a theoretical discussion only; I’m not saying it’s a good idea.

James