Z-Transform System Analysis

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Questions and Answers

What domain is represented by a sequence of values at discrete points in time?

  • Continuous time domain
  • Frequency domain
  • Discrete time domain (correct)
  • Z-domain

The Z-transform converts a signal from the continuous time domain to the Z-domain.

False (B)

What is the Z-transform of the unit step function, where $x[n] = 1$ for $n \geq 0$?

z/(z-1)

In the context of systems, what does a 'one sample delay' operation do to the output $y[n]$ relative to the input $u[n]$?

<p>Delays y[n] by one sample (C)</p> Signup and view all the answers

A system described as an 'Integrator' performs a summation of the input signal over time, resulting in an output that represents the ______ accumulation of past inputs.

<p>cumulative</p> Signup and view all the answers

Match the system operation with its corresponding Z-transform representation.

<p>Direct System (Output equals Input) = Y(z) = 1 One Sample Delay = Y(z) = z^{-1} Integrator = Y(z) = z/(z-1)</p> Signup and view all the answers

If a system is described by the equation $y[n] + 0.5y[n-1] = u[n]$, what is the transfer function $Y(z)/U(z)$ of the system in the Z-domain?

<p>$1/(1 + 0.5z^{-1})$ (A)</p> Signup and view all the answers

The Discrete-Time Fourier Transform (DTFT) transforms a signal from the Z-domain to the frequency domain.

<p>False (B)</p> Signup and view all the answers

Write the formula that represents the relationship between the Discrete-Time Fourier Transform $X(w)$ and the Z-transform $X(z)$ for a discrete signal $x[n]$.

<p>$X(w) = \sum_{n=-\infty}^{\infty} x[n]e^{-iwn}$ , $X(z) = \sum_{n=-\infty}^{\infty} x[n]z^{-n}$</p> Signup and view all the answers

For a finite-length signal, what concern is typically eliminated when computing its Z-transform?

<p>Convergence (D)</p> Signup and view all the answers

Given a finite length signal, the Z-transform is a finite ______, meaning that convergence issues are not a concern.

<p>sum</p> Signup and view all the answers

Consider the signal $x[k] = {1, 3, 2, -1}$ for $k = {-1, 0, 1, 2}$, respectively. What is the Z-transform $X(z)$ of this signal?

<p>$z + 3 + 2z - z^2$ (D)</p> Signup and view all the answers

The Z-transform of the sequence $x[k] = {1,3,2,-1}$ for $k = {-1, 0, 1, 2}$ is expressed as $Z^{-1}+3+2Z-Z^{2}$

<p>False (B)</p> Signup and view all the answers

Determine the expression for DTFT, $X(\Omega)$, if $X(z) = z + 3 + 2\cdot z^{-1} - z^{-2}$ .

<p>$e^{j\Omega} + 3 + 2e^{-j\Omega} - e^{-2j\Omega}$</p> Signup and view all the answers

In the expression $X(\Omega) = e^{j\Omega} + 3 + 2e^{-j\Omega} - e^{-2j\Omega}$, what substitution was made to derive it from the Z-transform $X(z)$?

<p>z = e^{j\Omega} (C)</p> Signup and view all the answers

Given $x[k] = {1, 3, 2, }$ for $k = {, 0, 1, 2}$, the term corresponding to $k=1$ in the Z-transform $X(z)$ is expressed as $2z^{blank}$

<p>-1</p> Signup and view all the answers

Match the operation with its Z-transform effect.

<p>Multiplication by $a^n$ = Scaling in the z-domain by $a$ Time Reversal = Replacing z with $z^{-1}$ Convolution = Multiplication of Z-transforms</p> Signup and view all the answers

Which property allows us to analyze systems by transforming differential equations into algebraic equations?

<p>Linearity (B)</p> Signup and view all the answers

The Z-transform of $x[n-1]$ is $zX(z)$, where $X(z)$ is the Z-transform of $x[n]$.

<p>False (B)</p> Signup and view all the answers

If the Z-transform of $x[n]$ is $X(z)$, what is the Z-transform of $x[n+k]$, where k is an integer?

<p>$z^k X(z)$</p> Signup and view all the answers

Flashcards

Z-Transform Definition

A mathematical transform used to analyze discrete-time signals and systems. It converts a discrete-time signal, which is a sequence of real or complex numbers, into a complex frequency-domain representation.

Z-Transform Formula

The formula to transform a discrete time domain signal x[n] into the z-domain.

System of 1

A system where the output at any time depends only on the input at that same time; mathematically represented as y[n] = u[n].

One sample delay

A system where the output is delayed by one time unit compared to the input; mathematically represented as y[n] = u[n-1].

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Integrator Definition

The system's output is the accumulation of all past input values, expressed as y[n] = y[n-1] + u[n].

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Discrete-Time Fourier Transform

A transform that decomposes a time-domain signal into its frequency components, but for discrete-time signals.

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DTFT as Z-Transform

A specific case of the Z-transform, used when analyzing the frequency content of a discrete-time signal.

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Finite Length Signal

A Z-Transform can be applied to a discrete signal x[k] that has a finite number of non-zero values. In this case, the region of convergence is the entire z-plane, except possibly at z=0 or z=∞.

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DTFT from Z-Transform

Given a Z-Transform X(z), we can find the DTFT by substituting z = e^(jΩ), where Ω is the discrete-time frequency variable.

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Study Notes

  • The Z Transform is used in discrete time domain analysis.
  • The Z Transform equation is: X(z) = sum(x[n] * z^(-n)) from n = -infinity to infinity.
  • The Z Transform is useful in analyzing and manipulating discrete-time signals and systems.

System Analysis using Z-Transform:

  • Considering a discrete-time system where u[n] is Input and y[n] is the output.
  • If the system's output y[n] is same as the input u[n], Y(z) = 1.

System with One Sample Delay:

  • For a system delaying the input by one sample, the output y[n] is a delayed version of the input u[n].
  • The Z-transform of the output can be expressed as Y(z) = z^(-1), or 1/z

Integrator System

  • If the system acts as an integrator, the output y[n] is the cumulative sum of the input u[n] up to time n.
  • For the integrator system, Y(z) = z / (z - 1).

System Described by Difference Equation:

  • Consider a system described by the difference equation: y[n] + 0.5y[n-1] = u[n].
  • Taking the Z-transform of the entire equation: Y(z) + 0.5z^(-1)Y(z) = U(z).
  • The system's transfer function Y(z)/U(z) = z / (z + 0.5).

Discrete-Time Fourier Transform vs. Z Transform

  • Discrete-Time Fourier Transform: X(ω) = sum(x[n] * e^(-jωn)) from n = -infinity to infinity.
  • Z-Transform: X(z) = sum(x[n] * z^(-n)) from n = -infinity to infinity.

Z-Transform Example

  • Find the Z-Transform X(z) for x[k] = {1, 3, 2, -1} for k = {-1, 0, 1, 2}.
  • Finite length signal, where X(z) = z + 3 + 2z^(-1) - z^(-2).
  • Find the DTFT of x[Ω]. X(Ω) = e^(jΩ) + 3 + 2e^(-jΩ) - e^(-2jΩ)

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