Question

(i) Draw the plot of amplitude versus `omega` for an amplitude modulated were whose carrier wave `(omega_(c))` is carrying two modulating signals, `omega_(1)` and `omega_(2)` `(omega_(2) gt omega_(1))`.
(ii) Is the plot symmetrical about `omega_(c)` ? Comment especially about plot in region `omega lt omega_(c)`.
(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?

Answer 1

(i) The plot of amplitude versus `omega` can be shown in the figure below

(ii) From figure, we note that frequency spectrum is not symmetrical about `omega_(c)`. Crowding of spectrum is present for `omega lt omega_(c)`.
(iii) If more waves are to be modulated then there will be more crowding in the modulating signal in the region `omega lt omega_(c)`. That will result more chances of mixing of signals.
(iv) To accommodate more signals, we should increase bandwidth and frequency carrier waves `omega_(c)`. This shows that large carrier frequency enables to carry more information (i.e., more `omega_(m)`) and the same will in turn increase bandwidth.