Question

Which of the following is an example for non- causal system?

(a) y[n] = ^1⁄3 {x[n-1] + x[n] + x[n-2]}

(b) y[n] = ^1⁄3 {x[n-1] + x[n] + x[n+1]}

(c) y[n] = ^1⁄2 {x[n-1] + x[n]}

(d) y[n] = ^1⁄2 {x[n] + x[n-2]}

I got this question in an online quiz.

My question comes from Properties of Systems in portion Signals and Systems Basics of Signals and Systems

Answer 1

Correct answer is (b) y[n] = ^1⁄3 {x[n-1] + x[n] + x[n+1]}

Best explanation: y[n] = ^1⁄3 {x[n-1] + x[n] + x[n+1]} is an example for non- causal system since the output y [n] depends on the future value of the input namely x [n+1].