Communication Systems - Engineering

Q1:

A wave is frequency modulated with an index of 0.1 and its frequency is multiplied by 8 times, the modulation index is

A not changed

B decreased 8 times

C increased 4 times

D increased 8 times

ANS:A - not changed

The effect of ntimes multiplier in fm.

modulation index(B) =n (B)
Fc=nFc
del f=n del f
fm =fm

in FM modulation index =del f/fm.

So new modulation index after multiplier =n (del f/fm).

So the right answer will be option D.