Question

Is the signal x(n) = u(n + 4) – u(n – 4) causal?

(a) YES

(b) NO

The question was asked in unit test.

Enquiry is from Signal Classification and Properties in division Signals and Systems Basics of Signals and Systems

Answer 1

Correct option is (b) NO

For explanation: A signal is said to be causal if it is 0 for t < 0.

⇒ u (n + 4) = 1 for n ≥ – 4

⇒ u(n – 4) = 1 for n ≥ 4

∴ The signal x (t) is defined for the interval [-4, 4] and it is zero for all other n values.

∵ The signal is defined for both n > 0 and n < 0

∴ The signal is non-causal.