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Electronics and Communication Engineering (ECE) : Signals and Systems - Quiz(MCQ)
When is a complex exponential signal pure DC?
A)
σ = 0 and Ω < 0
B)
σ = 0 and Ω = 0
C)
σ < 0 and Ω = 0
D)
σ < 0 and Ω < 0

Correct Answer : Option (B) :   σ = 0 and Ω = 0


Explanation : A complex exponential signal is represented as x(t)= est
Where, s = σ + jΩ
⇒ x(t) = eσt [cosΩt + jsinΩt] When, σ = 0 and Ω = 0 ⇒ x(t) = e0 [cos0 + jsin0] = 1 × 1 = 1 which is pure DC.

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