Question

A system has a receiver noise reactance of 50 Ω. It is connected to an antenna with an output resistance of 50 Ω. The noise figure of the system is:

1. 1
2. 2
3. 50
4. 101

Answer 1

Correct Answer - Option 2 : 2

Concept:

Noise figure (NF) or noise factor (F) are measures of degradation of the signal-to-noise ratio (SNR), caused by components in a signal chain.

The noise figure is given as:

\(NF= 1 + \frac{{{R_{eq}}}}{{{R_s}}}\)

Req = Equivalent resistance of antenna

Rs = Noise resistance of the system

Calculation:

With R_s = 50 Ω, and R_eq = 50 Ω, the noise figure will be:

\(NF= 1 + \frac{{{50}}}{{{50}}}\)

NF = 2