(New page: CT signal: <math>x(t) = 2\sin(2 \pi t) - (1 + 3j)\cos(5 \pi t)\,</math> <math>x(t) = 2 * \frac{e^{j2\pi t} - e^{-j2\pi t}}{2j} - (1 + 3j)*\frac{e^{j5\pi t} + e^{-j5\pi t}}{2}\,</math> ...)
 
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<math>x(t) = \frac{1}{j}e^{j2\pi t} - \frac{1}{j}e^{-j2\pi t} - \frac{1+3j}{2}e^{j3\pi t} - \frac{1+3j}{2}e^{j3\pi t}\,</math>
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<math>x(t) = \frac{1}{j}e^{j2\pi t} - \frac{1}{j}e^{-j2\pi t} - \frac{1+3j}{2}e^{j5\pi t} - \frac{1+3j}{2}e^{j5\pi t}\,</math>
  
  
  
<math>x(t) = \frac{2}{j}e^{5*j\pi t} - \frac{2}{j}e^{-5*j\pi t} - \frac{2+j}{2}e^{3*j\pi t} - \frac{2+j}{2}e^{-3*j\pi t}\,</math>
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<math>x(t) = \frac{1}{j}e^{2*j\pi t} - \frac{1}{j}e^{-2*j\pi t} - \frac{1+3j}{2}e^{5*j\pi t} - \frac{1+3j}{2}e^{-5*j\pi t}\,</math>
  
  
  
<math>\omega_0\,</math> ends up being <math>\pi\,</math> for this signal
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<math>\omega_0\,</math> = <math>\pi\,</math> therefore k = 2,-2,5,-5
  
So because of that, in my last step, i was able to determine what value of K's i had.  (k = 3,-3,5,-5)
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Applying the coefficients to get the <math>a_k\,</math>
  
So then you just take the coefficients of those terms to get the <math>a_k\,</math>
 
  
  
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<math>a_5 = \frac{-1-3j}{2}\,</math>    <math>a_{-5} = \frac{-1-3j}{2}\,</math>
  
Therefore:
 
  
  
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<math>a_2 = \frac{1}{j}\,</math>          <math>a_{-2} = \frac{-1}{j}\,</math>
  
<math>a_3 = \frac{-2-j}{2}\,</math>
 
  
  
 
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For K \neq [2,-2,-5,5], <math>a_k\, = 0</math>
<math>a_{-3} = \frac{-2-j}{2}\,</math>
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<math>a_5 = \frac{2}{j}\,</math>
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<math>a_{-5} = \frac{-2}{j}\,</math>
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For every other k:
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<math>a_k\, = 0</math>
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Revision as of 16:01, 26 September 2008

CT signal:

$ x(t) = 2\sin(2 \pi t) - (1 + 3j)\cos(5 \pi t)\, $


$ x(t) = 2 * \frac{e^{j2\pi t} - e^{-j2\pi t}}{2j} - (1 + 3j)*\frac{e^{j5\pi t} + e^{-j5\pi t}}{2}\, $


$ x(t) = \frac{1}{j}e^{j2\pi t} - \frac{1}{j}e^{-j2\pi t} - \frac{1+3j}{2}e^{j5\pi t} - \frac{1+3j}{2}e^{j5\pi t}\, $


$ x(t) = \frac{1}{j}e^{2*j\pi t} - \frac{1}{j}e^{-2*j\pi t} - \frac{1+3j}{2}e^{5*j\pi t} - \frac{1+3j}{2}e^{-5*j\pi t}\, $


$ \omega_0\, $ = $ \pi\, $ therefore k = 2,-2,5,-5

Applying the coefficients to get the $ a_k\, $


$ a_5 = \frac{-1-3j}{2}\, $ $ a_{-5} = \frac{-1-3j}{2}\, $


$ a_2 = \frac{1}{j}\, $ $ a_{-2} = \frac{-1}{j}\, $


For K \neq [2,-2,-5,5], $ a_k\, = 0 $

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Basic linear algebra uncovers and clarifies very important geometry and algebra.

Dr. Paul Garrett