# What is the power of unit step signal with magnitude A

## Homework Statement

Find power of signal A u(t)
A is constant like 5, 6 some value.[/B]

## Homework Equations

Power is integration over -T/2 to +T/2 of [x(t)]2 dt
The whole divide by T

## The Attempt at a Solution

Power is integration over -T/2 to +T/2 of [A u(t)]2dt[/B]
The whole divide by T

So 1/T integral A2 dt...integral limits are -T/2 to +T/2
This comes as 1/T A2 integral dt

integral dt is t. limits are -T/2 to +T/2
so integral dt = [T/2 - ( -T/2) ] which becomes T
so Poewr is 1/T * A2 * T
which gives A2

But book answer is A2 /2
Where did the divide by 2 come from?

Simon Bridge
Homework Helper
u(t)=1 when t>0 only.
integral is area under the graph - sketch the graph and see...

• jaus tail
LCKurtz
Homework Helper
Gold Member
What are ##T## and ##u(t)## in your problem?

• jaus tail
u(t) is unit function
u(t) =1 for t > 0 or t =0
u(t) = 0 otherwise.

T is just a random time value. So -T to +T is symmetric about y axis.

Ok now i get it. Since u(t) = 0 for negative time. the integral limit changes from (-T/2 to +T/2) to ( 0 to +T/2).
Got it. Thanks.

• Simon Bridge