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Signal and systems miscellaneous

Signals and Systems

  1. The impulse response of a system consists of two delta function as shown in the given figure.

    The input to the system is a unit amplitude square pulse of one unit time duration. Which one of the following depicts the correct output?
Correct Option: B

Given that impulse response i.e.

h(t) = 1.δ(t) –
1
δ(t – 1)
2


or H(s) = 1 –
1
e–s
2


Also, given x(t) = unit amplitude pulse of one unit time duration i.e.
or x(t) = u(t) – u(t – 1)

or X(s) =
1
-
1
e–s
ss


Now, Y(s) = H(s).X(s)

or Y(s) = 1 -
1
e–s
1
-
1
e–s
sss


or Y(s) =
1
-
1
.
1
e–s +
1
1
e–s
s2s2s


or Y(s) =
1
-
1
- e–s -
1
1
e–s +
1
1
e–2s
ss2s2s

Taking inverse Laplace transform

or y(t) = u(t) – u(t – 1) – 1/2 · u(t – 1) + 1/2 u(t – 2)
or y(t) = u(t) – 3/2 u(t – 1) + 1/2 u(t – 2)
Hence, alternative (B) is the correct choice.



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