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ECE 301, Homework #13, due date: 11/24/2010
http://cobweb.ecn.purdue.edu/
∼
chihw/10ECE301F/10ECE301F.html
Question 1:
Consider an AMDSB signal
y
(
t
) = (
x
(
t
) + 0
.
5)cos(3
πt
) is sent by a trans
mitter.
1. In what condition can we use
asynchronous demodulation
for the above system so
that
x
(
t
) can be reconstructed perfectly?
2. Suppose the receiver receives
y
(
t
) as follows. What is the end result if we use
asynchronous demodulation to construct the original signal
x
(
t
).
3
2
1
0
1
2
3
1.5
1
0.5
0
0.5
1
1.5
y(t)
t
3. The receiver realizes that the synchronous carrier at the receiver side is actually
sin(3
πt
) instead of cos(3
πt
). Explain why it changes from cos(3
πt
) to sin(3
πt
).
4. How to construct
x
(
t
) from
y
(
t
) using synchronous demodulation. Please describe
it by a diagram and explicitly specify all the frequencies involved.
5. What is the end result of using synchronous demodulation to reconstruct
x
(
t
)?
Question 2:
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This note was uploaded on 02/07/2011 for the course ECE 301 taught by Professor V."ragu"balakrishnan during the Fall '06 term at Purdue University.
 Fall '06
 V."Ragu"Balakrishnan

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