Causal LTI system question

Discussion in 'Homework Help' started by kaiosama, Feb 7, 2012.

  1. kaiosama

    kaiosama Thread Starter New Member

    Dec 6, 2010
    Here is a question in the textbook that I have no idea how to do:

    Consider a causal LTI system with input x[n] and output y[n]

    y[n] = 0.25 y[n-1] + x[n]

    Determine y[n] if x[n] = UnitImpulse[n-1]

    The solution starts off with "Since the system is causal, y[n] = 0 for n < 1".... but I don't understand how they are able to say that...Why do they say this?
  2. Zazoo

    Zazoo Member

    Jul 27, 2011
    Maine, USA
    A causal system will not be able to generate an output before an input is supplied. Since the shifted unit step input is zero for all values before n=1, the output of the causal system is also necessarily zero for all n less than 1.
Similar Threads
Forum Title Date
Homework Help Causal System or not ? Feb 25, 2014
Homework Help Causal or anti-causal? Dec 21, 2013
Homework Help Linear time invariant system - find output signal if transfer function is known Oct 8, 2014
Homework Help First order system ramp input Oct 3, 2014
Homework Help Need help on Passive Recovery System Designs For Rockets!! Oct 1, 2014

Share This Page