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Purdue Basics SIGNALS AND SYSTEMS

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ECE 301-003 and OL1, Homework #1 (CRN: 11474 and 26295)

Due date: Friday 1/29/2021

https://engineering.purdue.edu/~chihw/21ECE301S/21ECE301S.html

Review of calculus and arithmetics:

Question 1: Compute the values of the following integrals. You can leave your answers
in the form of trigonometric function values such as “cos(1.35).” There is no need to use
calculator to find the numerical value of the final answer.
∫ 3π
πω
sin(2ω + 0.5π + )dω
2π 2
∫ 3π
cos(π/3 − u)du
0
∫ 2 ∫ 2.5
3xπ yπ
cos( + )dxdy
y=1 x=0 4 3

Question 2: Compute the values of the following integrals.


∫ 4π
2−|t−π| e−j 2 t dt
π

−2π
∫ 3
π
ω cos( ω)dω
−2 3
∫ 3
(|z − 2|)ej2πz dz
−3

Question 3: Compute the values of the following integrals.


∫ 4
| cos(ω) − j(2ω + 1)|2 dω
1
∫ 5∫ 4 2
1

(2 − t) + j2√2t dsdt
3 3
Question 4: Compute the expressions of the following integrals.
∫ 2
ω
(t + 2s)e−jωπ(2t+s) ds
0
(∫ ∫ 2T )
T /2
1 T 2kπ T 2kπ
and ( − t)ej T t dt + (t − )ej T t dt ,
T −T 2 T /2 2

where k is an integer.

Question 5: Suppose f (s) = s2 + 2s − 3. Define g(t) = f (1 − t). Compute the following


values.

g(3)
∫ 5
g(1 + 2s)ds
2
∫ 3
and g ′ (s)ejπs ds,
0

where g ′ (t) is the first order derivative of g(t).

Question 6: Suppose f (t) = |1 − t|. Define


∫ t+2
g(t) = f (s)ds
t−1

Compute the following values.

g(3)
∫ 4
g(s)ds
1
∫ 1
and f (s)g(1 − s)ds.
−1

Question 7: Consider a discrete series f [n] = 2n + 1. Define


1
g[n] = kf [k − n]
k=−2
Compute the following values.

g[3]

1
4k g[k]
k=−2
∑∞
3−k−1 g[k + 1]
k=3

−2
and 2k g[k]
k=−∞

Hint: If |r| < 1, then we have the following formulas for computing the sum of a geometric
sequence.


a
ark−1 =
k=1
1−r


a
kark−1 = .
k=1
(1 − r)2

Question 8: Consider a discrete series f [n] = 3n − 1. Define


1
g[n] = (f [n] − f [−n]) . (1)
2
Compute the following values.

g[3]

1
and f [k]g[2 − k]
k=−1

Question 9: Consider a discrete series such that f [n] = 1 − j · |n| if −2 ≤ n ≤ 1 and


f [n] = 0 otherwise. Define



g[n] = f [n − k]2|k| .
k=−∞

Compute g[−3]. Find the expression of g[n].


Define


h[n] = f [k]2|n−k| .
k=−∞

Compute h[−3]. Find the expression of h[n].

Question 10: Suppose f (t) = cos(0.5πt − π). A discrete series g[n] is defined as

g[n] = f (6n).

Find the values of g[0], g[1], g[2], g[3]. [Optional] Find the expression of g[n] for general
n values.

Question 11: Suppose f [n] = (2n − 1)−2 . A function g(t) is defined as

g(t) = e−j2t (cos(t)f [3] + j sin(t)f [−1]).

Compute the following value


∫ π
|g(s)|2 ds.
−π/2

Question 12: Compute the following partial fractions:


1 a d
= + .
5− ω2− 6jω b + c · jω e + f · jω
Namely, find the real-valued coefficients a, b, c, d, e, and f .
Compute the following partial fractions:
1 3 − 2jω a d g
× = + + .
5− ω2− 6jω 1 − jω b + c · jω e + f · jω (b + c · jω)2

Namely, find the real-valued coefficients a, b, c, d, e, f , and g.

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