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<?xml version="1.0" encoding="UTF-8"?>
<!--
*
* This help file was generated from buttord.sci using help_from_sci().
*
-->
<refentry version="5.0-subset Scilab" xml:id="buttord" xml:lang="en"
xmlns="http://docbook.org/ns/docbook"
xmlns:xlink="http://www.w3.org/1999/xlink"
xmlns:svg="http://www.w3.org/2000/svg"
xmlns:ns3="http://www.w3.org/1999/xhtml"
xmlns:mml="http://www.w3.org/1998/Math/MathML"
xmlns:scilab="http://www.scilab.org"
xmlns:db="http://docbook.org/ns/docbook">
<refnamediv>
<refname>buttord</refname>
<refpurpose>Minimum filter order and 3dB cutoff frequency of a digital Butterworth filter with the desired response characteristics. </refpurpose>
</refnamediv>
<refsynopsisdiv>
<title>Calling Sequence</title>
<synopsis>
n = buttord(Wp, Ws, Rp, Rs)
[n, Wc] = buttord(Wp, Ws, Rp, Rs)
</synopsis>
</refsynopsisdiv>
<refsection>
<title>Parameters</title>
<variablelist>
<varlistentry><term>Wp:</term>
<listitem><para> scalar or vector of length 2 (passband edge(s)), elements must be in the range [0,1]</para></listitem></varlistentry>
<varlistentry><term>Ws:</term>
<listitem><para> scalar or vector of length 2 (stopband edge(s)), elements must be in the range [0,1]</para></listitem></varlistentry>
<varlistentry><term>Rp:</term>
<listitem><para> passband ripple in dB.</para></listitem></varlistentry>
<varlistentry><term>Rs:</term>
<listitem><para> stopband attenuation in dB.</para></listitem></varlistentry>
<varlistentry><term>n:</term>
<listitem><para> Minimum filter order satisfying specs.</para></listitem></varlistentry>
<varlistentry><term>Wc:</term>
<listitem><para> 3dB cutoff frequency/frequencies.</para></listitem></varlistentry>
</variablelist>
</refsection>
<refsection>
<title>Description</title>
<para>
This function computes the minimum filter order of a Butterworth filter with the desired response characteristics. </para>
<para>The filter frequency band edges are specified by the passband frequency wp and stopband frequency ws.</para>
<para>Frequencies are normalized to the Nyquist frequency in the range [0,1]. </para>
<para>Rp is measured in decibels and is the allowable passband ripple, and Rs is also in decibels and is the minimum attenuation in the stop band.</para>
<para>If ws>wp, the filter is a low pass filter. If wp>ws, the filter is a high pass filter.</para>
<para>If wp and ws are vectors of length 2, then the passband interval is defined by wp the stopband interval is defined by ws. </para>
<para>If wp is contained within the lower and upper limits of ws, the filter is a band-pass filter. If ws is contained within the lower and upper limits of wp the filter is a band-stop or band-reject filter.
</para>
</refsection>
<refsection>
<title>Examples</title>
<programlisting role="example"><![CDATA[
Wp = 40/500 ;
Ws = 150/500 ;
[n, Wc] = buttord(Wp, Ws, 3, 60)
]]></programlisting>
</refsection>
<refsection>
<title>Modified by :</title>
<simplelist type="vert">
<member>Sonu Sharma, RGIT Mumbai (fellow at FOSSEE, IIT Bombay)</member>
</simplelist>
</refsection>
</refentry>
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