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TN TRB EC 2012 Official Paper

Option 3 : 4.33

Network Theory

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30 Questions
40 Marks
40 Mins

The overall noise figure of cascade devices is \({F_n} = {F_1} + \frac{{{F_2} - 1}}{{{G_1}}} + \frac{{{F_3} - 1}}{{{G_1}{G_2}}} + \ldots + \frac{{{F_n} - 1}}{{{G_1}{G_2} \ldots {G_n}}}\;\)

We have,

gain = 10 dB = 10 and noise figure F = 6 dB = 100.6 = 3.98

Thus, overall noise figure:

\(\rm 3.98+\frac{3.98-1}{10} + \frac{3.98-1}{100} \)

= 4.32