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III. Gm-C Filtering - Epublications - Université de Limoges

III. Gm-C Filtering - Epublications - Université de Limoges

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A.4 Noise Factor and Noise Figure<br />

The noise factor is <strong>de</strong>fined [A.1] as the ratio of the SNR at the input and of the SNR at<br />

the output:<br />

SI / N I NO NO GkT0B + N R<br />

F = = = = (A.11)<br />

SO / NO GN I GkT0B GkT0B where NR is the noise ad<strong>de</strong>d by the receiver.<br />

It is worth highlighting that, for the <strong>de</strong>finition of the noise factor, NI is expressed as:<br />

NI = kT0B (A.12)<br />

where T0 is a standard temperature which value is 290°K.<br />

In electronics NF, which stands for Noise Figure, is also used. It has the following<br />

formula:<br />

( F )<br />

NF = 10log<br />

(A.13)<br />

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