Tanta University 1st year, Computers & Control Dept.
Faculty of Engineering Signals and Systems
Sheet 2
1. State whether the following system are static, linear, shift invariant, causal, and stable or not.
a. 𝑦(𝑡) = 𝑡 − 𝑥(𝑡 2 − 3)
b. 𝑦(𝑡) = 𝑥(𝑡 2 )
c. 𝑦(𝑡) = (𝑡 + 1)(0.5)𝑥(𝑡)
d. 𝑦(𝑛( = 𝑥(𝑡) cos (𝑥(𝑡 + 1))
e. 𝑦(𝑡) = (2)𝑡−1 𝑥(2𝑡 − 3)
f. 𝑦(𝑛) = 2𝑛 + 𝑥(𝑛2 + 2)
g. 𝑦(𝑛) = (0.5)𝑛+1 𝑥(𝑛)
h. 𝑦(𝑛( = 𝑥(𝑛) cos (𝑤𝑛 + 1)
i. 𝑦(𝑛) = 𝑥(𝑛) + 3𝑢(𝑛 + 1)
2. State whether the following system are causal or non-causal.
a. ℎ(𝑛) = { 1, 2, −1, 1, −0.5}
b. ℎ(𝑛) = {−1, 2, −1, 1, −0.5}
c. ℎ(𝑛) = 𝛿(𝑛) − 𝛿(−𝑛 − 1) − 2 𝛿(𝑛 − 1) + 𝛿(𝑛 − 3) + 𝛿(−𝑛 − 3)
3. Compute the linear convolution , 𝑦(𝑛) = 𝑥 (𝑛) ∗ ℎ(𝑛) , for the following sequences:
a. 𝑥(𝑛) = { 1, 2, −1} and ℎ(𝑛) = 𝑥(𝑛)
b. 𝑥(𝑛) = { 1, 2, 3, 4, 5 } and ℎ(𝑛) = { 1}
1, −1≤𝑛 ≤1
c. 𝑥(𝑛) = ℎ(𝑛) = {
0 , 𝑒𝑙𝑠𝑒𝑤ℎ𝑒𝑟𝑒
Dr. M. Arafa Signals and Systems Course
1 , 𝑛 = −2, 0, 1
d. 𝑥(𝑛) = { 2 , 𝑛 = −1 , and
0 𝑒𝑙𝑠𝑒𝑤ℎ𝑒𝑟𝑒
ℎ(𝑛) = 𝛿(𝑛 + 1) − 𝛿(𝑛 − 1) + 𝛿(𝑛 − 2)
e. 𝑥(𝑛) = {1 , −1 , 0 , 1 , 1} , and ℎ(𝑛) = 2𝑢(𝑛) − 2𝑢(𝑛 − 2)
f. 𝑥(𝑛) = 𝑢(𝑛) , and ℎ(𝑛) = 𝛿(𝑛) + 0.5 𝛿(𝑛 − 1) − 𝛿(𝑛 − 2)
4. Complete the following sentences:
a) If the input and output characteristics of the system change with shift of time, then the
system is called ……….. .
b) The type of system that needs a memory for its operations is called ……….. .
c) If the input output characteristics of the system change with shift of time, then the system
is called .………..
d) If the system output depends upon the future input values, then the system is called
.………..
e) The linear convolution is used to ………..
Dr. M. Arafa Signals and Systems Course