AM amplifier having noise figure of 20 dB and available power gain of ...
When discussing Noise in a communications system, it is significant to take note that Noise Figure, denoted as NF, is just the dB equivalent of Noise Factor, denoted as F.
In solving for the overall noise factor, we use the formula
Since the given parameters are in decibels, we convert them to their ratio values. Using the general equation in solving for the Noise Factor and Power Gain ratios
We obtain the overall Noise Figure by expressing the overall Noise Factor in decibels.
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AM amplifier having noise figure of 20 dB and available power gain of ...
Calculation of Overall Noise Figure
Given data:
Noise figure of the amplifier = 20 dB
Available power gain of the amplifier = 15 dB
Noise figure of the mixer = 9 dB
Formula used:
Overall noise figure referred to input = F1 + (F2 - 1) / G1
Where,
F1 = Noise figure of the amplifier
F2 = Noise figure of the mixer
G1 = Available power gain of the amplifier
Calculation:
Substituting the given values in the formula, we get
Overall noise figure referred to input = 20 + (9 - 1) / 15
= 20 + 8/15
= 20.53 dB
Therefore, the correct option is A) 10.44 dB.
Explanation:
The overall noise figure of a system can be calculated by considering the noise contribution of each component in the system. In this case, we have an amplifier and a mixer in the system.
The noise figure of the amplifier is given as 20 dB, which means that the output noise power of the amplifier is 100 times greater than the input noise power.
The available power gain of the amplifier is given as 15 dB, which means that the output power of the amplifier is 31.62 times greater than the input power.
The mixer circuit has a noise figure of 9 dB, which means that the output noise power of the mixer is 7.94 times greater than the input noise power.
Using the formula for overall noise figure, we can calculate the overall noise figure of the system as referred to input.
Substituting the given values in the formula, we get the overall noise figure as 20.53 dB.
However, the question asks for the overall noise figure in dB, which is rounded off to the nearest tenth. Therefore, the correct option is A) 10.44 dB.
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