(New page: Category:2010 Fall ECE 438 Boutin == Solution to Q4 of Week 5 Quiz Pool == ---- From the first question, we knew that <math> -a^{n}u[-n-1] = \mathcal{Z}^{-1}\bigg\{\frac{1}{1-az^{-...)
 
Line 4: Line 4:
 
----
 
----
  
From the first question, we knew that  
+
From the definition, we know that
  
<math> -a^{n}u[-n-1] = \mathcal{Z}^{-1}\bigg\{\frac{1}{1-az^{-1}}\bigg\} \text{ where } |z|<|a|. \,\!</math>
+
<math> H(e^{jw}) = \frac{e^{jw}-j}{e^{jw}-2} \,\!</math>
  
And the time-shifting property of Z-transform is defined as
+
<math> \text{For } w_1, \; |H(e^{j w_1})| = \bigg|\frac{e^{j\frac{\pi}{2}}-j}{e^{j\frac{\pi}{2}}-2}\bigg| = 0, \;\; \text{ since } e^{j\frac{\pi}{2}}=j. \,\!</math>
  
<math> x[n-k] = \mathcal{Z}^{-1}\bigg\{z^{-k}X(z)\bigg\} \text{   when  } x[n] = \mathcal{Z}^{-1}\bigg\{X(z)\bigg\}\,\!</math>
+
<math> \text{For } w_2, \; \text{ since } e^{-j\frac{\pi}{2}}=-j, \; H(e^{j w_2}) = \frac{e^{-j\frac{\pi}{2}}-j}{e^{-j\frac{\pi}{2}}-2} = \frac{-j-j}{-j-2} = \frac{2j}{2+j}.  \,\!</math>
 +
 
 +
Therefore,
 +
 
 +
<math> |H(e^{j w_2})| = \bigg|\frac{2j}{2+j}\bigg| = \frac{2}{\sqrt{5}}. \,\!</math>
  
Therefore, if we use the time-shifting property of Z-transform, then
 
  
<math> -a^{n-3}u[-(n-3)-1] = \mathcal{Z}^{-1}\bigg\{\frac{z^{-3}}{1-az^{-1}}\bigg\} \text{ where } |z|<|a|. \,\!</math>
 
  
Combined with the result from the linearity of Z-transform, then
 
  
<math>
 
\begin{align}
 
\mathcal{Z}^{-1}\bigg\{\frac{2z^{-3}}{1-az^{-1}}\bigg\}  \text{ for } |z|<|a| &= -2a^{n-3}u[-(n-3)-1], \\
 
&= -2a^{n-3}u[-n+2]
 
\end{align}
 
\,\!</math>
 
 
----
 
----
 
Back to [[ECE438_Week5_Quiz|Lab Week 5 Quiz Pool]]
 
Back to [[ECE438_Week5_Quiz|Lab Week 5 Quiz Pool]]

Revision as of 15:13, 19 September 2010


Solution to Q4 of Week 5 Quiz Pool


From the definition, we know that

$ H(e^{jw}) = \frac{e^{jw}-j}{e^{jw}-2} \,\! $

$ \text{For } w_1, \; |H(e^{j w_1})| = \bigg|\frac{e^{j\frac{\pi}{2}}-j}{e^{j\frac{\pi}{2}}-2}\bigg| = 0, \;\; \text{ since } e^{j\frac{\pi}{2}}=j. \,\! $

$ \text{For } w_2, \; \text{ since } e^{-j\frac{\pi}{2}}=-j, \; H(e^{j w_2}) = \frac{e^{-j\frac{\pi}{2}}-j}{e^{-j\frac{\pi}{2}}-2} = \frac{-j-j}{-j-2} = \frac{2j}{2+j}. \,\! $

Therefore,

$ |H(e^{j w_2})| = \bigg|\frac{2j}{2+j}\bigg| = \frac{2}{\sqrt{5}}. \,\! $




Back to Lab Week 5 Quiz Pool

Back to ECE 438 Fall 2010 Lab Wiki Page

Back to ECE 438 Fall 2010

Alumni Liaison

Ph.D. 2007, working on developing cool imaging technologies for digital cameras, camera phones, and video surveillance cameras.

Buyue Zhang