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Viewing changes to modules/signal_processing/help/en_US/remezb.xml

  • Committer: Package Import Robot
  • Author(s): Sylvestre Ledru
  • Date: 2012-08-30 14:42:38 UTC
  • mfrom: (1.4.7)
  • Revision ID: package-import@ubuntu.com-20120830144238-c1y2og7dbm7m9nig
Tags: 5.4.0-beta-3-1~exp1
* New upstream release
* Update the scirenderer dep
* Get ride of libjhdf5-java dependency

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modules/signal_processing/help/en_US/remezb.xml
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<?xml version="1.0" encoding="UTF-8"?>
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<refentry xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:svg="http://www.w3.org/2000/svg" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:db="http://docbook.org/ns/docbook" version="5.0-subset Scilab" xml:lang="en" xml:id="remezb">
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  <refnamediv>
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    <refname>remezb</refname>
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    <refpurpose> Minimax approximation of magnitude response</refpurpose>
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  </refnamediv>
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  <refsynopsisdiv>
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    <title>Calling Sequence</title>
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    <synopsis>[an]=remezb(nc,fg,ds,wt)</synopsis>
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  </refsynopsisdiv>
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  <refsection>
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    <title>Arguments</title>
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    <variablelist>
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      <varlistentry>
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        <term>nc</term>
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        <listitem>
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          <para>Number of cosine functions</para>
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        </listitem>
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      </varlistentry>
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      <varlistentry>
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        <term>fg</term>
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        <listitem>
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          <para>Grid of frequency points in [0,.5)</para>
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        </listitem>
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      </varlistentry>
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      <varlistentry>
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        <term>ds</term>
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        <listitem>
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          <para>
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            Desired magnitude on grid <literal>fg</literal>
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          </para>
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        </listitem>
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      </varlistentry>
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      <varlistentry>
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        <term>wt</term>
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        <listitem>
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          <para>
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            Weighting function on error on grid <literal>fg</literal>
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          </para>
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        </listitem>
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      </varlistentry>
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      <varlistentry>
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        <term>an</term>
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        <listitem>
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          <para>Cosine filter coefficients</para>
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        </listitem>
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      </varlistentry>
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    </variablelist>
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  </refsection>
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  <refsection>
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    <title>Description</title>
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    <para>
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      Minimax approximation of a frequency domain
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      magnitude response. The approximation takes
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      the form <literal>h = sum[a(n)*cos(wn)]</literal>
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      for n=0,1,...,nc. An FIR, linear-phase filter
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      can be obtained from the output of the function
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      by using the following commands
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    </para>
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    <programlisting role=""><![CDATA[ 
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hn(1:nc-1)=an(nc:-1:2)/2;
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hn(nc)=an(1);
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hn(nc+1:2*nc-1)=an(2:nc)/2;
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 ]]></programlisting>
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  </refsection>
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  <refsection>
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    <title>Examples</title>
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    <programlisting role="example"><![CDATA[ 
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// Choose the number of cosine functions and create a dense grid 
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// in [0,.24) and [.26,.5)
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nc=21;ngrid=nc*16;
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fg=.24*(0:ngrid/2-1)/(ngrid/2-1);
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fg(ngrid/2+1:ngrid)=fg(1:ngrid/2)+.26*ones(1:ngrid/2);
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// Specify a low pass filter magnitude for the desired response
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ds(1:ngrid/2)=ones(1:ngrid/2);
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ds(ngrid/2+1:ngrid)=zeros(1:ngrid/2);
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// Specify a uniform weighting function
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wt=ones(fg);
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// Run remezb
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an=remezb(nc,fg,ds,wt)
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// Make a linear phase FIR filter 
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hn(1:nc-1)=an(nc:-1:2)/2;
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hn(nc)=an(1);
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hn(nc+1:2*nc-1)=an(2:nc)/2;
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// Plot the filter's magnitude response
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plot(.5*(0:255)/256,frmag(hn,256));
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// Choose the number of cosine functions and create a dense grid in [0,.5)
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nc=21; ngrid=nc*16;
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fg=.5*(0:(ngrid-1))/ngrid;
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// Specify a triangular shaped magnitude for the desired response
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ds(1:ngrid/2)=(0:ngrid/2-1)/(ngrid/2-1);
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ds(ngrid/2+1:ngrid)=ds(ngrid/2:-1:1);
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// Specify a uniform weighting function
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wt=ones(fg);
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// Run remezb
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an=remezb(nc,fg,ds,wt)
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// Make a linear phase FIR filter 
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hn(1:nc-1)=an(nc:-1:2)/2;
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hn(nc)=an(1);
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hn(nc+1:2*nc-1)=an(2:nc)/2;
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// Plot the filter's magnitude response
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plot(.5*(0:255)/256,frmag(hn,256));
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 ]]></programlisting>
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  </refsection>
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  <refsection role="see also">
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    <title>See Also</title>
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    <simplelist type="inline">
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      <member>
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        <link linkend="eqfir">eqfir</link>
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      </member>
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    </simplelist>
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  </refsection>
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</refentry>