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  <name xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Continuous-Time Fourier Transform</name>
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  <md:version xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">1.1</md:version>
  <md:created xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">2004/06/10 16:47:24 GMT-5</md:created>
  <md:revised xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">2004/06/29 13:34:16.013 GMT-5</md:revised>
  <md:authorlist xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">
      <md:author xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="richb">
      <md:firstname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Richard</md:firstname>
      <md:othername xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">G.</md:othername>
      <md:surname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Baraniuk</md:surname>
      <md:email xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">richb@rice.edu</md:email>
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      <md:firstname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Harika</md:firstname>
      
      <md:surname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Basana</md:surname>
      <md:email xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">ilsai@rice.edu</md:email>
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    <md:maintainer xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="richb">
      <md:firstname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Richard</md:firstname>
      <md:othername xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">G.</md:othername>
      <md:surname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Baraniuk</md:surname>
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    <md:maintainer xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="jsilv">
      <md:firstname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Jeffrey</md:firstname>
      
      <md:surname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Silverman</md:surname>
      <md:email xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">jsilv@rice.edu</md:email>
    </md:maintainer>
    <md:maintainer xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="s001552">
      <md:firstname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Per</md:firstname>
      
      <md:surname xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Thorsteinsson</md:surname>
      <md:email xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">s001552@student.dtu.dk</md:email>
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  <md:abstract xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Introduction to the continuous-time Fourier Transform.</md:abstract>
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  <content xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">
    <para xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="begin">
      <name xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Theme:</name>
      Fourier representation for infinite-length "aperiodic" signals
    </para>
    <figure xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="f1">
      <name xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Fourier Series</name>
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    </figure>
    <figure xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="f2">
      <name xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">Fourier Transform</name>
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    </figure>
    <para xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="end">
      Alternative notations for CTFT:
      <m:math>
	<m:apply>
	  <m:ci type="fn">F</m:ci>
	  <m:ci>ω</m:ci>
	</m:apply>
      </m:math>
      and
      <m:math>
	<m:apply>
	  <m:ci type="fn">F</m:ci>
	  <m:apply>
	    <m:times/>
	    <m:imaginaryi/>
	    <m:ci>ω</m:ci>
	  </m:apply>
	</m:apply>
      </m:math>
    </para>
    <para xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="by">
      Recall that Fourier Series builds up
      <emphasis xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">periodic</emphasis> or<emphasis xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/"> finite
      length</emphasis> signal from sum of <emphasis xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">harmonic
      sinusoids</emphasis> with frequencies that are multiples of
      <m:math>
	<m:apply>
	  <m:eq/>
	  <m:ci>
	    <m:msub>
	      <m:mi>ω</m:mi>
	      <m:mi>o</m:mi>
	    </m:msub>
	  </m:ci>
	  <m:apply>
	    <m:divide/>
	    <m:apply>
	      <m:times/>
	      <m:cn>2</m:cn>
	      <m:pi/>
	    </m:apply>
	    <m:ci>T</m:ci>
	  </m:apply>
	</m:apply>
      </m:math>
    </para>
    <para xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="the">
      CTFT builds up arbitrary signal from sum of sinusoids of
      <emphasis xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">all</emphasis> frequencies
      <m:math>
	<m:apply>
	  <m:in/>
	  <m:ci>ω</m:ci>
	  <m:reals/>
	</m:apply>
      </m:math>
    
      <equation xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="way">
	<m:math>
	  <m:apply>
	    <m:eq/>
	    <m:apply>
	      <m:ci type="fn">F</m:ci>
	      <m:apply>
		<m:times/>
		<m:imaginaryi/>
		<m:ci>ω</m:ci>
	      </m:apply>
	    </m:apply>
	    <m:apply>
	      <m:int/>
	      <m:bvar><m:ci>t</m:ci></m:bvar>
	      <m:lowlimit>
		<m:apply>
		  <m:minus/>
		  <m:infinity/>
		</m:apply>
	      </m:lowlimit>
	      <m:uplimit>
		<m:infinity/>
	      </m:uplimit>
	      <m:apply>
		<m:times/>
		<m:apply>
		  <m:ci type="fn">f</m:ci>  
		  <m:ci>t</m:ci>
		</m:apply>
		<m:apply>
		  <m:exp/>
		  <m:apply>
		    <m:minus/>
		    <m:apply>
		      <m:times/>
		      <m:imaginaryi/>
		      <m:ci>ω</m:ci>
		      <m:ci>t</m:ci>
		    </m:apply>
		  </m:apply>
		</m:apply>
	      </m:apply>
	    </m:apply>
	  </m:apply>
	</m:math>
      </equation>

      <equation xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="way12">
	<m:math>
	  <m:apply>
	    <m:eq/>
	    <m:apply>
	      <m:ci type="fn">f</m:ci>  
	      <m:ci>t</m:ci>
	    </m:apply>
	    <m:apply>
	      <m:times/>
	      <m:apply>
		<m:divide/>
		<m:cn>1</m:cn>
		<m:apply>
		  <m:times/>
		  <m:cn>2</m:cn>
		  <m:pi/>
		</m:apply>
	      </m:apply>
	      <m:apply>
		<m:int/>
		<m:bvar><m:ci>ω</m:ci></m:bvar>
		<m:lowlimit>
		  <m:apply>
		    <m:minus/>
		    <m:infinity/>
		  </m:apply>
		</m:lowlimit>
		<m:uplimit>
		  <m:infinity/>
		</m:uplimit>
		<m:apply>
		  <m:times/>
		<m:apply>
		    <m:ci type="fn">F</m:ci>
		    <m:apply>
		      <m:times/>
		      <m:imaginaryi/>
		      <m:ci>ω</m:ci>
		    </m:apply>
		  </m:apply>
		  <m:apply>
		    <m:exp/>
		    <m:apply>
		      <m:times/>
		      <m:imaginaryi/>
		      <m:ci>ω</m:ci>
		      <m:ci>t</m:ci>
		    </m:apply>
		  </m:apply>
		</m:apply>
	      </m:apply>
	    </m:apply>
	  </m:apply>
	</m:math>
      </equation>
      <note xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/">CTFT is totally symmetrical except for the 
	<m:math>
	  <m:apply>
	    <m:divide/>
	    <m:cn>1</m:cn>
	    <m:apply>
	      <m:times/>
	      <m:cn>2</m:cn>
	      <m:pi/>
	    </m:apply>
	  </m:apply>
	</m:math> goes with 
	<m:math>
	<m:ci>δω</m:ci>
	</m:math>
      </note>
      Alternate normalizations include :
      <list xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/" id="hyewr">
	<item xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/"> 
	   <m:math>
	    <m:apply>
	      <m:divide/>
	      <m:cn>1</m:cn>
	      <m:apply>
		<m:root/>
		<m:apply>
		  <m:times/>
		  <m:cn>2</m:cn>
		  <m:pi/>
		</m:apply>
	      </m:apply>
	    </m:apply>
	  </m:math> in both the above equations.
	</item>
	<item xmlns:md="http://cnx.rice.edu/mdml/0.4" xmlns:m="http://www.w3.org/1998/Math/MathML" xmlns:bib="http://bibtexml.sf.net/"> Do not use rad/sec frequency 
	  <m:math>
	    <m:ci>ω</m:ci>
	  </m:math> but rather Hz frequency 
	  <m:math>
	    <m:ci>γ</m:ci>
	  </m:math>. Then all the
	  <m:math>
	    <m:apply>
	      <m:divide/>
	      <m:cn>1</m:cn>
	      <m:apply>
		<m:times/>
		<m:cn>2</m:cn>
		<m:pi/>
	      </m:apply>
	    </m:apply>
	  </m:math>'s go away.
	  
	</item>
      </list>
    </para>
  </content>
</document>
