1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Causal system/convolution question

  1. Oct 20, 2014 #1
    1. The problem statement, all variables and given/known data

    a) find if the system is causal.
    b) find the impulse response

    given: y(t)=x(t-1)u(t)

    ans:
    a) Causal
    b) delta(t-1)

    2. Relevant equations


    3. The attempt at a solution

    a)

    I thought this is a non-causal system because if our input is delta(t), the resultant output is delta(t-1)
    if t=1, input value depends on delta(1), and its output is delta(0). output depends on future value.


    b) I don't know where that u(t) comes from...


    thanks.
     
  2. jcsd
  3. Oct 21, 2014 #2

    RUber

    User Avatar
    Homework Helper

    Usually this type of problem will the additional condition that x(t) = 0 for t<0, so that it is more clear that this is a weighted ( by u(t) ) shift operation.
    I am assuming that x and u are known and y is the output.
     
  4. Oct 21, 2014 #3

    FOIWATER

    User Avatar
    Gold Member

    a) The system is causal because the output is only dependent on past values of input x[t-1] is a time in the past.

    b) y[t]=x[t-1]*u[t] --> for the impulse response, we put delta function as input (x) and then solve for output. so, impulse response:
    h[t] = delta[t-1]*u[t] = delta[t-1]
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Causal system/convolution question
  1. Causal system (Replies: 0)

  2. Causal Systems (Replies: 2)

  3. Causal System ? (Replies: 3)

Loading...