Signals and Systems - Engineering

Q1:

which one is discrete time periodic signal?

A
sin 3pn

B
cos 2pn

C
sin 3pn

D all

ANS:C -

sin 3pn

In Discrete time signal irrational function cannot be periodic, frequency must be rational. Hence only (c) is periodic. sin 3pn = sin 3p(n + N) ⇒ for Periodic 3pN = 2Kp .