Sarthaks Test
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(i) Draw the plot of amplitude versus ‘ω’ for an amplitude modulated wave whose carrier wave (ωc) is carrying two modulating signals, ω1 and ω22 > ω1). [Hint: Follow derivation from Eq 15.6 of NCERT Textbook of XII] 

(ii) Is the plot symmetrical about ωc? Comment especially about plot in region ω < ωc

(iii) Extrapolate and predict the problems one can expect if more waves are to be modulated. 

(iv) Suggest solutions to the above problem. In the process can one understand another advantage of modulation in terms of bandwidth?

1 Answer

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(i) Plot of amplitude versus w is shown in the Figure.

(ii) As can be seen, the frequency spectrum is not symmetrical about ωc. Crowding of the spectrum is present for ω < ωc

(iii) Adding more modulating signals lead to more crowding in ω < ωc and more chances of mixing of signals. in 

(iv) Increase bandwidth and ωc to accommodate more signals. This shows that large carrier frequency enables to carry more information (more ωm) and which will in turn increase bandwidth.

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