signals and systems

Thread Starter

juhir

Joined Jul 6, 2008
3
for each of the following signals determine whether this signals are periodic or not?If periodic find fundamental period.

a. x(t)= cos2(2piet)
b.x(t)= (-1)^n
 

thingmaker3

Joined May 16, 2005
5,083
What have you come up with thus far in your own efforts?

One way to solve these problems is to make a graph of the function. You will be able to tell whether they are periodic, and will be able to calculate any period easily.

Another way to solve these problems is to compare the function to known periodic functions and look for similarities.
 

Dave

Joined Nov 17, 2003
6,969
Simple intuition should illstrate that one signal is periodic, whereas the other is not. Btw, I think you have a misplaced "2" in question a).

Dave
 

roddefig

Joined Apr 29, 2008
149
You can prove that a signal is periodic if it repeats itself. The way to describe this concept mathematically is:

\(
x(t) = x(t+T)
\)

Basically, x(t) is equal to itself \(T\) seconds later. You can generalize this as follows

\(
x(t) = x(t+nT) \ \forall\ n
\)

x(t) is equal to itself every \(nT\) seconds, where \(n\) is any integer.

If I remember my linear systems class correctly satisfying the first equation is enough to prove periodicity, but I would check with your notes to see what your professor wants.
 
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