Is u[n] - u[n-4] a power or energy signal?

[smart_worker]

Homework Statement

Determine whether u[n] - u[n-4] is a power or energy signal.

Homework Equations

The Attempt at a Solution

I am stuck here. I don't know how to simply further. Please help.

 

[lewando]

You could tell by inspection based on the definitions of "energy signal" and "power signal". If you want to use that formula, what can you say about the equivalence of u[n] - u[n-4] and |u[n] - u[n-4]|² ?

 

[smart_worker]

You could tell by inspection based on the definitions of "energy signal" and "power signal". If you want to use that formula, what can you say about the equivalence of u[n] - u[n-4] and |u[n] - u[n-4]|² ?

I think u[n] - u[n-4] = 1 for n=0,1,2,3 and 0 elsewhere.
So, E_x becomes 4. So, it's an Energy Signal. Am I right?

 

[lewando]

I think u[n] - u[n-4] = 1 for n=0,1,2,3 and 0 elsewhere.
So, E_x becomes 4.

That is exactly right.

So, it's an Energy Signal.

You might want to indicate (for others who might want to follow your logic) what is so special about "4" that leads you to classify the signal as you have. What if the result was "5"?