Mercurial > hg > ltpda

comparison m-toolbox/html_help/help/ug/sigproc_iir.html @ 0:f0afece42f48

Find changesets by keywords (author, files, the commit message), revision number or hash, or revset expression.
Import.
author Daniele Nicolodi <nicolodi@science.unitn.it>
date Wed, 23 Nov 2011 19:22:13 +0100
parents
children
comparison
equal deleted inserted replaced
-1:000000000000 0:f0afece42f48
1 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
2 "http://www.w3.org/TR/1999/REC-html401-19991224/loose.dtd">
3
4 <html lang="en">
5 <head>
6 <meta name="generator" content=
7 "HTML Tidy for Mac OS X (vers 1st December 2004), see www.w3.org">
8 <meta http-equiv="Content-Type" content=
9 "text/html; charset=us-ascii">
10
11 <title>IIR Filters (LTPDA Toolbox)</title>
12 <link rel="stylesheet" href="docstyle.css" type="text/css">
13 <meta name="generator" content="DocBook XSL Stylesheets V1.52.2">
14 <meta name="description" content=
15 "Presents an overview of the features, system requirements, and starting the toolbox.">
16 </head>
17
18 <body>
19 <a name="top_of_page" id="top_of_page"></a>
20
21 <p style="font-size:1px;">&nbsp;</p>
22
23 <table class="nav" summary="Navigation aid" border="0" width=
24 "100%" cellpadding="0" cellspacing="0">
25 <tr>
26 <td valign="baseline"><b>LTPDA Toolbox</b></td><td><a href="../helptoc.html">contents</a></td>
27
28 <td valign="baseline" align="right"><a href=
29 "sigproc_dfilt.html"><img src="b_prev.gif" border="0" align=
30 "bottom" alt="Digital Filtering"></a>&nbsp;&nbsp;&nbsp;<a href=
31 "sigproc_fir.html"><img src="b_next.gif" border="0" align=
32 "bottom" alt="FIR Filters"></a></td>
33 </tr>
34 </table>
35
36 <h1 class="title"><a name="f3-12899" id="f3-12899"></a>IIR Filters</h1>
37 <hr>
38
39 <p>
40 <p>
41 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
42 </p>
43 <div align="center">
44 <IMG src="images/sigproc_7.png" width="283" height="56" align="middle" border="0">
45 </div>
46 <p>
47 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].
48 </p>
49 <h2><a name="IIRbuild">Creating a IIR filter in the LTPDA</a></h2>
50
51 The LTPDA Toolbox allows the implementation of IIR filters by means of the <a href="pzmodel_filter.html"> miir class</a>.
52
53 <h2><a name="IIRplist">Creating from a plist</a></h2>
54 <p>
55 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.
56 </p>
57 <div class="fragment"><pre>
58
59 pl = plist(<span class="string">'type'</span>, <span class="string">'highpass'</span>, ...
60 <span class="string">'order'</span>, 1, ...
61 <span class="string">'gain'</span>, 2.0, ...
62 <span class="string">'fs'</span>, 10, ...
63 <span class="string">'fc'</span>, 0.2);
64 f = miir(pl)
65 </pre></div>
66
67 <h2><a name="IIRpzmodel">Creating from a pzmodel</a></h2>
68 <p>
69 IIR filters can also be <a href="pzmodel_filter.html"> created from a pzmodel </a>.
70 </p>
71 <h2><a name="IIRdiff">Creating from a difference equation</a></h2>
72 <p>
73 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:
74 </p>
75
76 <div align="center">
77 <IMG src="images/sigproc_9.png" width="299" height="28" align="middle" border="0">
78 </div>
79
80 <p><br></p>
81
82 <div class="fragment"><pre>
83
84 a = [0.5 -0.01];
85 b = [1 0.1];
86 fs = 1;
87 f = miir(a,b,fs)
88 </pre></div>
89
90 <p>
91 <br>
92 Notice that the convetion used in this function is the one described in the <a href="sigproc_dfilt.html"> Digital filters classification</a> section
93 </p>
94
95 <h2><a name="IIRimport">Importing an existing model</a></h2>
96 <p>
97 The miir constructor also accepts as an input existing models in different formats:
98 </p>
99 <li>
100 <li><p>LISO files:<p>
101 <div class="fragment"><pre>
102 f = miir(<span class="string">'foo_iir.fil'</span>)
103 </pre></div>
104 </li>
105 <li><p>XML files:</p>
106 <div class="fragment"><pre>
107 f = miir(<span class="string">'foo_iir.xml'</span>)
108 </pre></div>
109 <li><p>MAT files:</p>
110 <div class="fragment"><pre>
111 f = miir(<span class="string">'foo_iir.mat'</span>)
112 </pre></div>
113 </li>
114 <li><p>From repository:</p>
115 <div class="fragment"><pre>
116 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>, []))
117 </pre></div>
118 </li>
119 </ul>
120
121
122 </p>
123
124 <br>
125 <br>
126 <table class="nav" summary="Navigation aid" border="0" width=
127 "100%" cellpadding="0" cellspacing="0">
128 <tr valign="top">
129 <td align="left" width="20"><a href="sigproc_dfilt.html"><img src=
130 "b_prev.gif" border="0" align="bottom" alt=
131 "Digital Filtering"></a>&nbsp;</td>
132
133 <td align="left">Digital Filtering</td>
134
135 <td>&nbsp;</td>
136
137 <td align="right">FIR Filters</td>
138
139 <td align="right" width="20"><a href=
140 "sigproc_fir.html"><img src="b_next.gif" border="0" align=
141 "bottom" alt="FIR Filters"></a></td>
142 </tr>
143 </table><br>
144
145 <p class="copy">&copy;LTP Team</p>
146 </body>
147 </html>