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Viewing changes to modules/signal_processing/help/en_US/filters/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/filters/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>