Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

i need to sketch y[n] where * denotes the convolution operator and delta is the unit impulse. I know how to sketch x[n-1] and delta[n-2] but i have problems with the convolution. In my script i only found this formula for convolution with delta pulses.

\begin{aligned} z[n] * \delta[n-n0] & = z[n-n0] \\ \end{aligned}

But it doesn't help me at all...

\begin{aligned} x[n] & = (\frac{1}{2})^n (u[n+1]-u[n-3]) \\ y[n] & = x[n-1] * \delta[n-2] \end{aligned}

Maybe someone can help me. ;-)
And is there an easy way to prove my sketches?
Wolfram Alpha doesn't work i think.

share|cite|improve this question
up vote 2 down vote accepted

Write explicitly $X[m] = x[m-1]$ as a function of $n$ and put $m = n-2$.

share|cite|improve this answer
Well, i am a beginner in dsp. I do not know exactly what u mean. Shall i just sketch x[n-3] ? – madmax Apr 14 '11 at 13:11
Sure, but I just described the logics which leads to this result. – Ilya Apr 14 '11 at 13:17
That's all? Ok, i trust u. ;-) Till now i don't really know what i am doing ... – madmax Apr 14 '11 at 13:26

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.