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NCERT Class XII Chapter
Communication Systems
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Question : 7
Total: 8
For an amplitude modulated wave, the maximum amplitude is found to be 10 V while the minimum amplitude is found to be 2 V. Determine the modulation index, µ. What would be the value of µ if the minimum amplitude is zero volt?
Solution:  
We know
Modulation index, µ =
Am
Ac
Also, minimum amplitude, Amin = Ac (1− m)
Maximum amplitude, Amax = Ac (1+ m)
So, modulation index
µ =
Amax−Amin
Amax+Amin
or µ =
10−2
10+2
 =
8
12
 = 2/3 = 0.67
If Amin = 0, then modulation index,
µ =
Amax−Amin
Amax+Amin
 =
10−0
10+0
 =
10
10
 = 1
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