Revision as of 08:39, 19 April 2011 by Ssanthak (Talk | contribs)


Practice Question on signal modulation

Let x(t) be a signal whose Fourier transform $ {\mathcal X} (\omega) $ satisfies

$ {\mathcal X} (\omega)=0 \text{ when }|\omega| > 1,000 \pi . $

The signal x(t) is modulated with the complex exponential carrier

$ c(t)= e^{j \omega_c t }. $

a) What conditions should be put on ωc to insure that x(t) can be recovered from the modulated signal x(t)c(t)?

b) Assuming the condition you stated in a) are met, how can one recover x(t) from the modulated signal x(t)c(t)?


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Answer 1

a) ωc > 0

b) to recover x(t) from x(t)c(t), multiply x(t)c(t) by $ e^{-j \omega_c t }. $

--Cmcmican 20:56, 7 April 2011 (UTC)

Answer 2

a) wc > wm

    wc > 1000pi

b)Since y(t) = x(t) e^jwct

        So x(t) = y(t) e^-jwct

   so to demodulate multiply by e^-jwct

--Ssanthak 12:39, 19 April 2011 (UTC)

Answer 3

Write it here.


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