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author Daniele Nicolodi <nicolodi@science.unitn.it>
date Wed, 23 Nov 2011 19:22:13 +0100
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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>
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7 "HTML Tidy for Mac OS X (vers 1st December 2004), see www.w3.org">
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10
11 <title>Generating model noise (LTPDA Toolbox)</title>
12 <link rel="stylesheet" href="docstyle.css" type="text/css">
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15 "Presents an overview of the features, system requirements, and starting the toolbox.">
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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 "builtin_models.html"><img src="b_prev.gif" border="0" align=
30 "bottom" alt="Built-in models of LTPDA"></a>&nbsp;&nbsp;&nbsp;<a href=
31 "franklin_ng.html"><img src="b_next.gif" border="0" align=
32 "bottom" alt="Franklin noise-generator"></a></td>
33 </tr>
34 </table>
35
36 <h1 class="title"><a name="f3-12899" id="f3-12899"></a>Generating model noise</h1>
37 <hr>
38
39 <p>
40 <p>
41
42 Generating non-white random noise means producing arbitrary long time series with a given spectral density.
43 Such time series are needed for example for the following purposes:
44 </p>
45 <p>
46 <ul>
47 <li> To generate test data sets for programs that compute spectral densities, </li>
48 <li> as inputs for various simulations.</li>
49 </ul>
50 </p>
51 <p>
52 One way of doing this is to apply digital filters (FIR or IIR) to white input noise.<br/>
53 This approach is effectively implemented for the generation of <a href="ndim_ng.html"> multichannel noise </a>
54 with a given cross spectral density. <br/>
55 Multichannel transfer functions are identified by an automatic fit procedure based
56 on a modified version of the vector-fitting algorithm
57 (see <a href="zdomainfit.html"> Z-Domain Fit </a> for further details on the algorithm). <br/>
58 Partial fraction expansion of multichannel transfer functions and the implementation of
59 <a href="sigproc_dfilt.html">filter</a> state initialization avoid the presence of unwanted 'warm-up period'.
60 </p>
61
62 <p>
63 A different approach is implemented in LTPDA as <a href="franklin_ng.html">Franklin noise-generator</a>.<br/>
64 It produces spectral densities according to a given pole zero model (see <a href="pzmodel.html">Pole/Zero Modeling</a>) and does not require any warm-up period. <br/>
65 </p>
66
67 </p>
68
69 <br>
70 <br>
71 <table class="nav" summary="Navigation aid" border="0" width=
72 "100%" cellpadding="0" cellspacing="0">
73 <tr valign="top">
74 <td align="left" width="20"><a href="builtin_models.html"><img src=
75 "b_prev.gif" border="0" align="bottom" alt=
76 "Built-in models of LTPDA"></a>&nbsp;</td>
77
78 <td align="left">Built-in models of LTPDA</td>
79
80 <td>&nbsp;</td>
81
82 <td align="right">Franklin noise-generator</td>
83
84 <td align="right" width="20"><a href=
85 "franklin_ng.html"><img src="b_next.gif" border="0" align=
86 "bottom" alt="Franklin noise-generator"></a></td>
87 </tr>
88 </table><br>
89
90 <p class="copy">&copy;LTP Team</p>
91 </body>
92 </html>