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(ELEC211)[2010](sum)quiz~2105^_10307.pdf
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ELEC211Si l dS t
ELEC 211 Signals and Systems
Review Short Questions
Chapters 1-55
Chapters 1
Albert Wongg
Chapters 1 2
Chapters 1 --2
Question 1 -Which of the following is NOT a
compp
lex sinusoid?
. jt
(a) () () = ee 8
(a) xtxt
1
. (2 + j )t
(b) xt() = e 8
(b) () 8
j2 n
j
(c) (c) xnxn[] =
[] ee
j(( 2 + ) n
(d) [] = ej 3)
xn
The Hong Kong University of Science and Technolog
Department of Electrical and Electronic Engineering
Question 3 Which of the following is correct if
y[n]=w[[
n]*[[
nn--33]?
y[]] ]
aa.
y[n]=w[3]
y[n]=w[3]
b y[n]y[n]=w[n+3]
b.
w[n+3]
c.
y[n]=w[n3]
y[n]=w[n--3]
d. y[3]=1, otherwise =0
The Hong Kong University of Science and Technolog
Department of Electrical and Electronic Engineering
Question 4 -Which of the following impulse response
is causal AND stable?
hh((tt)) hh((tt))
(c)
h(t)(a) (b)
tt t
t
Chapters 1-2 -Answers
Chapters 1 2 Answers
1.
(b) C it is a general complex exponential; Also, (c) is
(b) Cit is a general complex exponential; Also, (c) is not strictly speaking periodic C it is something that
we will not encounter in this course and it is not
par
ticticu
llarl
ly
meaningfmeaningful
l tto
discdiscuss it
it
2. (d)
33.
()
(c)
4. (b)
5 ()(a) C th
the
iintegral on
ththe RHS is a
ffuncti
tion o
ff . It
It
5.
l RHSi
integrates away t.
Chapter 3
QuestionQuestion 11 --What is the FS of
cosot ?
11
(a)
a = , a =. , and a = 0,for k 1,.1
1 .1 k
2 j 2 j
11
(b)
a1 = , a. =. , and a = 0,for k 1,.1
2 122 k
2
(c)
a = 1, a = 1 , and a = 0,for k 1,.1
(c)
11 .11 kk
2 j 22 j
2 jj
(d)(d)
a 12 , a.1 = 12 and aa = 00,forfor k 1 .1
a = a , and k 1, 1
1 k
The Hong Kong University of Science and Technolog
Department of Electrical and Electronic Engineering
Question 2 -
Which of the following is a valid
Which of the following Fourier Series analyy
sis eqq
uation?
. jk t
(a) ()) = akk 8
() xt( e
k
3
13 . jj t
1 88
(b) a = x(t)e ddt
(b) 33 ()
0
1
1
1 16. jt
(c) a4 = x() 2
te dt
0
16
92
. jk n
() xn e 8
(d) [] = akk
k = 2
The Hong Kong University of Science and Technolog
Department of Electrical and Electronic Engineering
Question 3 -What is the FS coefficients of
Question 3 What is the FS coefficients of
the shifted periodic impulse train
xt = t .nT .
()( )
n=.
(a)
ak =1/T
(b)
ak (1
=.)/ T
2
.jk
(c)
akk =eT / T
(d)
ak =1/(T .)
The Hong Kong University of Science and Technolog
Department of Electrical and Electronic Engineering
Question 4 C x[n] has a period of N and is real
Question 4 x[n] has a period of N and is real,
and let ak be its FS coefficients. Which of the
and let a
following statements is not necessarily true?
f