Wednesday, February 29, 2012

Homework - 9

Answer the following questions by referring to the text book :

  1. Can we connect two LTI systems, with impulse responces h1[n] and h2[n], in series ? What will be the output y[n] in such a case ?
  2. Extend the above understanding on how to calculate the overall response when independent LTIs are connected in a complex arrangement of series and parallel connections.
  3. What do you understand about Region of Convergence (RoC) ?
  4. Explain why the z-Transform is incomplete (without RoC) in defining the z-domain representation of a given time-domain function. Given examples.
  5. What are the properties of z-Transform ?
  6. Locate the z-Transforms and RoC for the following functions from your text book :
    1. Impulse function delta[n]
    2. Step function u[n]
    3. Increasing function a^n u[n]. Read a^n as a raised to the power of n.
    4. n (a^n) u[n]
    5. -a^n. u[-n-1]
    6. -na^n u[-n-1]
  7. Note : The inverse z-Transform can be computed by any one of the following methods :
    1. Direct evaluation
    2. Expansion into a series of terms in the variables z, and z^-1
    3. Partial-fraction expansion and table lookups.
Good Day

2 comments:

  1. Related to Q1

    Can we connect two LTI systems, with impulse responces h1[n] and h2[n], in series ? What will be the output y[n] in such a case ?

    Yes we can connect two LTI systems in series (cascade).
    Output in such case when impulse is sent as an input signal is:

    y(n) = -inf to +inf Σh1(k)h2(n-k) or equivalently
    y(n) = -inf to +inf Σh2(k)h1(n-k)

    Sir please let me know if my understanding is right.

    ReplyDelete
  2. x[n] ---> h1[n]--h2[n]-----> y[n]

    y[n] = x[n]*h1[n]*h2[n] where * indicates convolution operation.

    So, what you wrote is correct except that you have not included the input x[n].

    You can find y[n] in two ways.
    First find h1[n]*h2[n].

    Then find x[n]* {result of the above convolution operation}

    ReplyDelete