(New page: Category:2010 Fall ECE 438 Boutin ---- == Solution to Q1 of Week 13 Quiz Pool == ---- Suppose <math>X(w)\,\!</math> is the DTFT of a discrete-time signal <math>x[n]\,\!</math>. What...)
 
 
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Suppose <math>X(w)\,\!</math> is the DTFT of a discrete-time signal <math>x[n]\,\!</math>.
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Suppose <math>X(\omega)\,\!</math> is the DTFT of a discrete-time signal <math>x[n]\,\!</math>.
  
What is the DTFT of the time-reversal <math>x[-n]</math>?
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What is the DTFT of the time-reversal <math>x[-n]\,\!</math>?
  
<math>\begin{align} & \sum_{n=-\inty}^{\infty} x[-n]e^{-jwn} \\ & \quad (\text{change of variable} \;\; m=-n) \\ = & \sum_{m=-\inty}^{\infty} x[m]e^{jwm} = X(-w) \\ \end{align}</math>
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<math>\begin{align} & \sum_{n=-\infty}^{\infty} x[-n]e^{-j\omega n} \\ & \quad (\text{change of variable} \;\; m=-n) \\ = & \sum_{m=-\infty}^{\infty} x[m]e^{j\omega m} = X(-\omega) \\ \end{align}</math>
  
 
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Latest revision as of 10:24, 17 November 2010



Solution to Q1 of Week 13 Quiz Pool


Suppose $ X(\omega)\,\! $ is the DTFT of a discrete-time signal $ x[n]\,\! $.

What is the DTFT of the time-reversal $ x[-n]\,\! $?

$ \begin{align} & \sum_{n=-\infty}^{\infty} x[-n]e^{-j\omega n} \\ & \quad (\text{change of variable} \;\; m=-n) \\ = & \sum_{m=-\infty}^{\infty} x[m]e^{j\omega m} = X(-\omega) \\ \end{align} $


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