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CITY UNIVERSITY OF
HONG
KONG
 
Course code
&
title
:
EE3008 Principles of Communications
Session
:
Semester
A
200712008
Time allowed
:
Two hours


This paper has FIVE pages (including this cover page).
1.
This paper consists of FOUR questions.
2.
Attempt all the FOUR questions.
3.
Start a new page in the answering script for each question.
...............................................................................................
Materials, aids
&
instruments permitted to be used during examination:
1.
Nonprogrammable portable batteryoperated calculator
Special materials (other than standard materials e.g. answer book or
supplementary sheets) to be supplied to students:
Nil
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View Full DocumentQuestion
1) (25 marks)
Consider the following transmission method based on fir) shown in Fig.1. The data
rate is 2.5kblsec. Let the transmitted signal
.
s(t)
=
sl(t)
=
AAt) if information bit "1" is transmitted, and
.
s(r)
=
so(i)
=
BAt) if information bit
"0"
is transmitted,
where A and B are real constants. The probabilities of sending "0" and "1" are equal.
The received signal is r(i)=s(t)+n(t), where n(t) represents channel noise. An optimal
correlation receiver is shown in Fig. 2.
Fig. 1
Sampling at
t=T
Fig.2
decision device
reference signal
At)
(a)
Determine the value of T above.
[2 marks]
(b)
Find the expression for the spectrum offit). (Hint: Treat fir) as a rectangular
pulse plus its delayed version with reversed sign. The Fourier transform of a
rectangular
pulse g(t) with nonzero
duration
[212,
2/21
is given by
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 Fall '08
 PingLi

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