Mercurial > hg > ltpda
view m-toolbox/html_help/help/ug/sigproc_iir.html @ 47:dd93c9ba6624 database-connection-manager
Fix Java dialog
author | Daniele Nicolodi <nicolodi@science.unitn.it> |
---|---|
date | Tue, 06 Dec 2011 19:07:27 +0100 |
parents | f0afece42f48 |
children |
line wrap: on
line source
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd"> <html lang="en"> <head> <meta name="generator" content= "HTML Tidy for Mac OS X (vers 1st December 2004), see www.w3.org"> <meta http-equiv="Content-Type" content= "text/html; charset=us-ascii"> <title>IIR Filters (LTPDA Toolbox)</title> <link rel="stylesheet" href="docstyle.css" type="text/css"> <meta name="generator" content="DocBook XSL Stylesheets V1.52.2"> <meta name="description" content= "Presents an overview of the features, system requirements, and starting the toolbox."> </head> <body> <a name="top_of_page" id="top_of_page"></a> <p style="font-size:1px;"> </p> <table class="nav" summary="Navigation aid" border="0" width= "100%" cellpadding="0" cellspacing="0"> <tr> <td valign="baseline"><b>LTPDA Toolbox</b></td><td><a href="../helptoc.html">contents</a></td> <td valign="baseline" align="right"><a href= "sigproc_dfilt.html"><img src="b_prev.gif" border="0" align= "bottom" alt="Digital Filtering"></a> <a href= "sigproc_fir.html"><img src="b_next.gif" border="0" align= "bottom" alt="FIR Filters"></a></td> </tr> </table> <h1 class="title"><a name="f3-12899" id="f3-12899"></a>IIR Filters</h1> <hr> <p> <p> Infinite Impulse Response filters are those filters present a non-zero infinite length response when excited with a very brief (ideally an infinite peak) input signal. A linear causal IIR filter can be described by the following difference equation </p> <div align="center"> <IMG src="images/sigproc_7.png" width="283" height="56" align="middle" border="0"> </div> <p> This operation describe a recursive system, i.e. a system that depends on current and past samples of the input x[n], but also on the output data stream y[n]. </p> <h2><a name="IIRbuild">Creating a IIR filter in the LTPDA</a></h2> The LTPDA Toolbox allows the implementation of IIR filters by means of the <a href="pzmodel_filter.html"> miir class</a>. <h2><a name="IIRplist">Creating from a plist</a></h2> <p> The following example creates an order 1 highpass filter with high frequency gain 2. Filter is designed for 10 Hz sampled data and has a cut-off frequency of 0.2 Hz. </p> <div class="fragment"><pre> pl = plist(<span class="string">'type'</span>, <span class="string">'highpass'</span>, ... <span class="string">'order'</span>, 1, ... <span class="string">'gain'</span>, 2.0, ... <span class="string">'fs'</span>, 10, ... <span class="string">'fc'</span>, 0.2); f = miir(pl) </pre></div> <h2><a name="IIRpzmodel">Creating from a pzmodel</a></h2> <p> IIR filters can also be <a href="pzmodel_filter.html"> created from a pzmodel </a>. </p> <h2><a name="IIRdiff">Creating from a difference equation</a></h2> <p> Alternatively, the filter can be defined in terms of two vectors specifying the coefficients of the filter and the sampling frequency. The following example creates a IIR filter with sampling frequency 1 Hz and the following recursive equation: </p> <div align="center"> <IMG src="images/sigproc_9.png" width="299" height="28" align="middle" border="0"> </div> <p><br></p> <div class="fragment"><pre> a = [0.5 -0.01]; b = [1 0.1]; fs = 1; f = miir(a,b,fs) </pre></div> <p> <br> Notice that the convetion used in this function is the one described in the <a href="sigproc_dfilt.html"> Digital filters classification</a> section </p> <h2><a name="IIRimport">Importing an existing model</a></h2> <p> The miir constructor also accepts as an input existing models in different formats: </p> <li> <li><p>LISO files:<p> <div class="fragment"><pre> f = miir(<span class="string">'foo_iir.fil'</span>) </pre></div> </li> <li><p>XML files:</p> <div class="fragment"><pre> f = miir(<span class="string">'foo_iir.xml'</span>) </pre></div> <li><p>MAT files:</p> <div class="fragment"><pre> f = miir(<span class="string">'foo_iir.mat'</span>) </pre></div> </li> <li><p>From repository:</p> <div class="fragment"><pre> f = miir(plist(<span class="string">'hostname'</span>, <span class="string">'localhost'</span>, <span class="string">'database'</span>, <span class="string">'ltpda'</span>, <span class="string">'ID'</span>, [])) </pre></div> </li> </ul> </p> <br> <br> <table class="nav" summary="Navigation aid" border="0" width= "100%" cellpadding="0" cellspacing="0"> <tr valign="top"> <td align="left" width="20"><a href="sigproc_dfilt.html"><img src= "b_prev.gif" border="0" align="bottom" alt= "Digital Filtering"></a> </td> <td align="left">Digital Filtering</td> <td> </td> <td align="right">FIR Filters</td> <td align="right" width="20"><a href= "sigproc_fir.html"><img src="b_next.gif" border="0" align= "bottom" alt="FIR Filters"></a></td> </tr> </table><br> <p class="copy">©LTP Team</p> </body> </html>