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<math>y[n]=h[n]*x[n]=\sum_{k=-\infty}^\infty \frac{1}{5^k}u[k]u[n-k]=\sum_{k=0}^\infty \frac{1}{5^k}u[n-k]=\Bigg( \sum_{k=0}^n \frac{1}{5^k} \Bigg)u[n]</math>
 
<math>y[n]=h[n]*x[n]=\sum_{k=-\infty}^\infty \frac{1}{5^k}u[k]u[n-k]=\sum_{k=0}^\infty \frac{1}{5^k}u[n-k]=\Bigg( \sum_{k=0}^n \frac{1}{5^k} \Bigg)u[n]</math>
  
Right here I run into the same problem that I had with the original problem.  I don't know how to compute this sum. If it were an infinite sum I could compute it, but it's not. I can't find any references that tell me how to compute this sum in non-infinite form. I tried convolving in the opposite order, but came up with <math>\Bigg( \sum_{k=0}^n \frac{1}{5^{n-k}} \Bigg)u[n]</math> which is no better (as far as I can tell).  Is there something I am missing?  How do I compute this sum??????
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I'm not totally sure that this is the way to compute this sum...
  
--[[User:Cmcmican|Cmcmican]] 20:53, 31 January 2011 (UTC)
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<math>y[n]=\Bigg(\frac{1-(1/5)^{n+1}}{1-(1/5)}\Bigg)u[n]</math>
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--[[User:Cmcmican|Cmcmican]] 20:57, 31 January 2011 (UTC)
  
 
===Answer 2===
 
===Answer 2===

Revision as of 16:57, 31 January 2011

Practice Question on Computing the Output of an LTI system by Convolution

The unit impulse response h[n] of a DT LTI system is

$ h[n]= \frac{1}{5^n}u[n]. \ $

Use convolution to compute the system's response to the input

$ x[n]= u[n] \ $


Share your answers below

You will receive feedback from your instructor and TA directly on this page. Other students are welcome to comment/discuss/point out mistakes/ask questions too!


Answer 1

$ y[n]=h[n]*x[n]=\sum_{k=-\infty}^\infty \frac{1}{5^k}u[k]u[n-k]=\sum_{k=0}^\infty \frac{1}{5^k}u[n-k]=\Bigg( \sum_{k=0}^n \frac{1}{5^k} \Bigg)u[n] $

I'm not totally sure that this is the way to compute this sum...

$ y[n]=\Bigg(\frac{1-(1/5)^{n+1}}{1-(1/5)}\Bigg)u[n] $

--Cmcmican 20:57, 31 January 2011 (UTC)

Answer 2

Write it here.

Answer 3

Write it here.


Back to ECE301 Spring 2011 Prof. Boutin

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Ph.D. 2007, working on developing cool imaging technologies for digital cameras, camera phones, and video surveillance cameras.

Buyue Zhang