scilab/modules/signal_processing/help/en_US/wigner.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <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" xmlns:scilab="http://www.scilab.org"  version="5.0-subset Scilab" xml:lang="en" xml:id="wigner">
   3     <refnamediv>
   4         <refname>wigner</refname>
   5         <refpurpose> 'time-frequency' wigner spectrum</refpurpose>
   6     </refnamediv>
   7     <refsynopsisdiv>
   8         <title>Calling Sequence</title>
   9         <synopsis>[tab]=wigner(x,h,deltat,zp)</synopsis>
  10     </refsynopsisdiv>
  11     <refsection>
  12         <title>Arguments</title>
  13         <variablelist>
  14             <varlistentry>
  15                 <term>tab</term>
  16                 <listitem>
  17                     <para>wigner spectrum (lines correspond to the time variable)</para>
  18                 </listitem>
  19             </varlistentry>
  20             <varlistentry>
  21                 <term>x</term>
  22                 <listitem>
  23                     <para>analyzed signal</para>
  24                 </listitem>
  25             </varlistentry>
  26             <varlistentry>
  27                 <term>h</term>
  28                 <listitem>
  29                     <para>data window</para>
  30                 </listitem>
  31             </varlistentry>
  32             <varlistentry>
  33                 <term>deltat</term>
  34                 <listitem>
  35                     <para>analysis time increment (in samples)</para>
  36                 </listitem>
  37             </varlistentry>
  38             <varlistentry>
  39                 <term>zp</term>
  40                 <listitem>
  41                     <para>
  42                         length of FFT's. <literal>%pi/zp</literal> gives the frequency increment.
  43                     </para>
  44                 </listitem>
  45             </varlistentry>
  46         </variablelist>
  47     </refsection>
  48     <refsection>
  49         <title>Description</title>
  50         <para>
  51             function which computes the 'time-frequency' wigner
  52             spectrum of a signal.
  53         </para>
  54     </refsection>
  55     <refsection>
  56         <title>Sample</title>
  57         <scilab:image>
  58             a=[488^2 488 1;408^2 408 1;568^2 568 1];
  59             b=[1.28;0;0];
  60             x=a\b;
  61             t=408:568;
  62             p=x'*[t.*t;t;ones(t)];
  63             u=[0*ones(408:487) ones(488:568)];
  64             s=p.*sin(2*%pi/16*t+u*%pi);
  65             s=[0*ones(0:407) s 0*ones(569:951)];
  66             h=ones(1,64);
  67             w=wigner(s,h,12,128);
  68             scf();
  69             plot3d(1:69,1:64,abs(w(1:69,1:64)));
  70         </scilab:image>
  71     </refsection>
  72
  73     <refsection>
  74         <title>Examples</title>
  75         <programlisting role="example"><![CDATA[
  76 a=[488^2 488 1;408^2 408 1;568^2 568 1];
  77 b=[1.28;0;0];
  78 x=a\b;
  79 t=408:568;
  80 p=x'*[t.*t;t;ones(t)];
  81 // unit step function
  82 u=[0*ones(408:487) ones(488:568)];
  83 // finite duration sinusoid
  84 s=p.*sin(2*%pi/16*t+u*%pi);
  85 // signal to be analyzed
  86 s=[0*ones(0:407) s 0*ones(569:951)];
  87 // 64-point rectangular window
  88 h=ones(1,64);
  89 // wigner spectrum
  90 w=wigner(s,h,12,128);
  91 scf();
  92 plot3d(1:69,1:64,abs(w(1:69,1:64)));
  93  ]]></programlisting>
  94     </refsection>
  95
  96 </refentry>