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<h1>gri_iir.h</h1> </div>
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<a href="gri__iir_8h.html">Go to the documentation of this file.</a><div class="fragment"><pre class="fragment"><a name="l00001"></a>00001 <span class="comment">/* -*- c++ -*- */</span>
<a name="l00002"></a>00002 <span class="comment">/*</span>
<a name="l00003"></a>00003 <span class="comment"> * Copyright 2002 Free Software Foundation, Inc.</span>
<a name="l00004"></a>00004 <span class="comment"> * </span>
<a name="l00005"></a>00005 <span class="comment"> * This file is part of GNU Radio</span>
<a name="l00006"></a>00006 <span class="comment"> * </span>
<a name="l00007"></a>00007 <span class="comment"> * GNU Radio is free software; you can redistribute it and/or modify</span>
<a name="l00008"></a>00008 <span class="comment"> * it under the terms of the GNU General Public License as published by</span>
<a name="l00009"></a>00009 <span class="comment"> * the Free Software Foundation; either version 3, or (at your option)</span>
<a name="l00010"></a>00010 <span class="comment"> * any later version.</span>
<a name="l00011"></a>00011 <span class="comment"> * </span>
<a name="l00012"></a>00012 <span class="comment"> * GNU Radio is distributed in the hope that it will be useful,</span>
<a name="l00013"></a>00013 <span class="comment"> * but WITHOUT ANY WARRANTY; without even the implied warranty of</span>
<a name="l00014"></a>00014 <span class="comment"> * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the</span>
<a name="l00015"></a>00015 <span class="comment"> * GNU General Public License for more details.</span>
<a name="l00016"></a>00016 <span class="comment"> * </span>
<a name="l00017"></a>00017 <span class="comment"> * You should have received a copy of the GNU General Public License</span>
<a name="l00018"></a>00018 <span class="comment"> * along with GNU Radio; see the file COPYING. If not, write to</span>
<a name="l00019"></a>00019 <span class="comment"> * the Free Software Foundation, Inc., 51 Franklin Street,</span>
<a name="l00020"></a>00020 <span class="comment"> * Boston, MA 02110-1301, USA.</span>
<a name="l00021"></a>00021 <span class="comment"> */</span>
<a name="l00022"></a>00022
<a name="l00023"></a>00023 <span class="preprocessor">#ifndef INCLUDED_GRI_IIR_H</span>
<a name="l00024"></a>00024 <span class="preprocessor"></span><span class="preprocessor">#define INCLUDED_GRI_IIR_H</span>
<a name="l00025"></a>00025 <span class="preprocessor"></span>
<a name="l00026"></a>00026 <span class="preprocessor">#include <vector></span>
<a name="l00027"></a>00027 <span class="preprocessor">#include <stdexcept></span>
<a name="l00028"></a>00028 <span class="comment"></span>
<a name="l00029"></a>00029 <span class="comment">/*!</span>
<a name="l00030"></a>00030 <span class="comment"> * \brief base class template for Infinite Impulse Response filter (IIR)</span>
<a name="l00031"></a>00031 <span class="comment"> */</span>
<a name="l00032"></a>00032 <span class="keyword">template</span><<span class="keyword">class</span> i_type, <span class="keyword">class</span> o_type, <span class="keyword">class</span> tap_type>
<a name="l00033"></a><a class="code" href="classgri__iir.html">00033</a> <span class="keyword">class </span><a class="code" href="classgri__iir.html" title="base class template for Infinite Impulse Response filter (IIR)">gri_iir</a> {
<a name="l00034"></a>00034 <span class="keyword">public</span>:<span class="comment"></span>
<a name="l00035"></a>00035 <span class="comment"> /*!</span>
<a name="l00036"></a>00036 <span class="comment"> * \brief Construct an IIR with the given taps.</span>
<a name="l00037"></a>00037 <span class="comment"> *</span>
<a name="l00038"></a>00038 <span class="comment"> * This filter uses the Direct Form I implementation, where</span>
<a name="l00039"></a>00039 <span class="comment"> * \p fftaps contains the feed-forward taps, and \p fbtaps the feedback ones.</span>
<a name="l00040"></a>00040 <span class="comment"> *</span>
<a name="l00041"></a>00041 <span class="comment"> * \p fftaps and \p fbtaps must have equal numbers of taps</span>
<a name="l00042"></a>00042 <span class="comment"> *</span>
<a name="l00043"></a>00043 <span class="comment"> * The input and output satisfy a difference equation of the form</span>
<a name="l00044"></a>00044 <span class="comment"></span>
<a name="l00045"></a>00045 <span class="comment"> \f[</span>
<a name="l00046"></a>00046 <span class="comment"> y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]</span>
<a name="l00047"></a>00047 <span class="comment"> \f]</span>
<a name="l00048"></a>00048 <span class="comment"></span>
<a name="l00049"></a>00049 <span class="comment"> * with the corresponding rational system function</span>
<a name="l00050"></a>00050 <span class="comment"></span>
<a name="l00051"></a>00051 <span class="comment"> \f[</span>
<a name="l00052"></a>00052 <span class="comment"> H(z) = \frac{\sum_{k=0}^{N} b_k z^{-k}}{1 - \sum_{k=1}^{M} a_k z^{-k}}</span>
<a name="l00053"></a>00053 <span class="comment"> \f]</span>
<a name="l00054"></a>00054 <span class="comment"></span>
<a name="l00055"></a>00055 <span class="comment"> * Note that some texts define the system function with a + in the denominator.</span>
<a name="l00056"></a>00056 <span class="comment"> * If you're using that convention, you'll need to negate the feedback taps.</span>
<a name="l00057"></a>00057 <span class="comment"> */</span>
<a name="l00058"></a><a class="code" href="classgri__iir.html#a79ac3f84ffeb3c6190b249a639b0f2ca">00058</a> <a class="code" href="classgri__iir.html#a9e7ea537a27b610aa96ba407be82831d">gri_iir</a> (<span class="keyword">const</span> <a class="code" href="classstd_1_1vector.html">std::vector<tap_type></a>& fftaps,
<a name="l00059"></a>00059 <span class="keyword">const</span> <a class="code" href="classstd_1_1vector.html">std::vector<tap_type></a>& fbtaps) <span class="keywordflow">throw</span> (std::invalid_argument)
<a name="l00060"></a>00060 {
<a name="l00061"></a>00061 <a class="code" href="classgri__iir.html#abbc8febf2bccd566121688c66b0b0326" title="install new taps.">set_taps</a> (fftaps, fbtaps);
<a name="l00062"></a>00062 }
<a name="l00063"></a>00063
<a name="l00064"></a><a class="code" href="classgri__iir.html#a9e7ea537a27b610aa96ba407be82831d">00064</a> <a class="code" href="classgri__iir.html#a9e7ea537a27b610aa96ba407be82831d">gri_iir</a> () : <a class="code" href="classgri__iir.html#af7e5eba6e33011c68e168a1b75ed2baa">d_latest_n</a>(0),<a class="code" href="classgri__iir.html#a325cbd21166ec28dc27ca0feccef7b38">d_latest_m</a>(0) { }
<a name="l00065"></a>00065
<a name="l00066"></a><a class="code" href="classgri__iir.html#a50545f86e1ab90ef36893d3a2b81fb2f">00066</a> <a class="code" href="classgri__iir.html#a50545f86e1ab90ef36893d3a2b81fb2f">~gri_iir</a> () {}
<a name="l00067"></a>00067 <span class="comment"></span>
<a name="l00068"></a>00068 <span class="comment"> /*!</span>
<a name="l00069"></a>00069 <span class="comment"> * \brief compute a single output value.</span>
<a name="l00070"></a>00070 <span class="comment"> * \returns the filtered input value.</span>
<a name="l00071"></a>00071 <span class="comment"> */</span>
<a name="l00072"></a>00072 o_type <a class="code" href="classgri__iir.html#adb60d3d25c5fce9278d8f2cd5e3c74cb" title="compute a single output value.">filter</a> (<span class="keyword">const</span> i_type input);
<a name="l00073"></a>00073 <span class="comment"></span>
<a name="l00074"></a>00074 <span class="comment"> /*!</span>
<a name="l00075"></a>00075 <span class="comment"> * \brief compute an array of N output values.</span>
<a name="l00076"></a>00076 <span class="comment"> * \p input must have N valid entries.</span>
<a name="l00077"></a>00077 <span class="comment"> */</span>
<a name="l00078"></a>00078 <span class="keywordtype">void</span> <a class="code" href="classgri__iir.html#aef452a0ffbc9d9040b08d58d0bbe0589" title="compute an array of N output values. input must have N valid entries.">filter_n</a> (o_type output[], <span class="keyword">const</span> i_type input[], <span class="keywordtype">long</span> n);
<a name="l00079"></a>00079 <span class="comment"></span>
<a name="l00080"></a>00080 <span class="comment"> /*!</span>
<a name="l00081"></a>00081 <span class="comment"> * \return number of taps in filter.</span>
<a name="l00082"></a>00082 <span class="comment"> */</span>
<a name="l00083"></a><a class="code" href="classgri__iir.html#a82e9ff44853cc878f317b5405e786038">00083</a> <span class="keywordtype">unsigned</span> <a class="code" href="classgri__iir.html#a82e9ff44853cc878f317b5405e786038">ntaps_ff</a> ()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> <a class="code" href="classgri__iir.html#aadd595c780fc6b2ee50c7c8b3eb5eea3">d_fftaps</a>.size (); }
<a name="l00084"></a><a class="code" href="classgri__iir.html#afe39444b015e40596401bc98c613264b">00084</a> <span class="keywordtype">unsigned</span> <a class="code" href="classgri__iir.html#afe39444b015e40596401bc98c613264b">ntaps_fb</a> ()<span class="keyword"> const </span>{ <span class="keywordflow">return</span> <a class="code" href="classgri__iir.html#ae270ca4360515fbd80cf9ad513b96f24">d_fbtaps</a>.size (); }
<a name="l00085"></a>00085 <span class="comment"></span>
<a name="l00086"></a>00086 <span class="comment"> /*!</span>
<a name="l00087"></a>00087 <span class="comment"> * \brief install new taps.</span>
<a name="l00088"></a>00088 <span class="comment"> */</span>
<a name="l00089"></a><a class="code" href="classgri__iir.html#abbc8febf2bccd566121688c66b0b0326">00089</a> <span class="keywordtype">void</span> <a class="code" href="classgri__iir.html#abbc8febf2bccd566121688c66b0b0326" title="install new taps.">set_taps</a> (<span class="keyword">const</span> <a class="code" href="classstd_1_1vector.html">std::vector<tap_type></a> &fftaps,
<a name="l00090"></a>00090 <span class="keyword">const</span> <a class="code" href="classstd_1_1vector.html">std::vector<tap_type></a> &fbtaps) <span class="keywordflow">throw</span> (std::invalid_argument)
<a name="l00091"></a>00091 {
<a name="l00092"></a>00092
<a name="l00093"></a>00093
<a name="l00094"></a>00094 <a class="code" href="classgri__iir.html#af7e5eba6e33011c68e168a1b75ed2baa">d_latest_n</a> = 0;
<a name="l00095"></a>00095 <a class="code" href="classgri__iir.html#a325cbd21166ec28dc27ca0feccef7b38">d_latest_m</a> = 0;
<a name="l00096"></a>00096 <a class="code" href="classgri__iir.html#aadd595c780fc6b2ee50c7c8b3eb5eea3">d_fftaps</a> = fftaps;
<a name="l00097"></a>00097 <a class="code" href="classgri__iir.html#ae270ca4360515fbd80cf9ad513b96f24">d_fbtaps</a> = fbtaps;
<a name="l00098"></a>00098
<a name="l00099"></a>00099 <span class="keywordtype">int</span> n = fftaps.size ();
<a name="l00100"></a>00100 <span class="keywordtype">int</span> m = fbtaps.size ();
<a name="l00101"></a>00101 <a class="code" href="classgri__iir.html#aac5a985051761be98d5753f5a1542003">d_prev_input</a>.resize (2 * n);
<a name="l00102"></a>00102 <a class="code" href="classgri__iir.html#a566a5d039cf32bb27a750b123e8dae7a">d_prev_output</a>.resize (2 * m);
<a name="l00103"></a>00103
<a name="l00104"></a>00104 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 0; i < 2 * n; i++){
<a name="l00105"></a>00105 <a class="code" href="classgri__iir.html#aac5a985051761be98d5753f5a1542003">d_prev_input</a>[i] = 0;
<a name="l00106"></a>00106 }
<a name="l00107"></a>00107 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 0; i < 2 * m; i++){
<a name="l00108"></a>00108 <a class="code" href="classgri__iir.html#a566a5d039cf32bb27a750b123e8dae7a">d_prev_output</a>[i] = 0;
<a name="l00109"></a>00109 }
<a name="l00110"></a>00110 }
<a name="l00111"></a>00111
<a name="l00112"></a>00112 <span class="keyword">protected</span>:
<a name="l00113"></a><a class="code" href="classgri__iir.html#aadd595c780fc6b2ee50c7c8b3eb5eea3">00113</a> <a class="code" href="classstd_1_1vector.html">std::vector<tap_type></a> <a class="code" href="classgri__iir.html#aadd595c780fc6b2ee50c7c8b3eb5eea3">d_fftaps</a>;
<a name="l00114"></a><a class="code" href="classgri__iir.html#ae270ca4360515fbd80cf9ad513b96f24">00114</a> <a class="code" href="classstd_1_1vector.html">std::vector<tap_type></a> <a class="code" href="classgri__iir.html#ae270ca4360515fbd80cf9ad513b96f24">d_fbtaps</a>;
<a name="l00115"></a><a class="code" href="classgri__iir.html#af7e5eba6e33011c68e168a1b75ed2baa">00115</a> <span class="keywordtype">int</span> <a class="code" href="classgri__iir.html#af7e5eba6e33011c68e168a1b75ed2baa">d_latest_n</a>;
<a name="l00116"></a><a class="code" href="classgri__iir.html#a325cbd21166ec28dc27ca0feccef7b38">00116</a> <span class="keywordtype">int</span> <a class="code" href="classgri__iir.html#a325cbd21166ec28dc27ca0feccef7b38">d_latest_m</a>;
<a name="l00117"></a><a class="code" href="classgri__iir.html#a566a5d039cf32bb27a750b123e8dae7a">00117</a> <a class="code" href="classstd_1_1vector.html">std::vector<tap_type></a> <a class="code" href="classgri__iir.html#a566a5d039cf32bb27a750b123e8dae7a">d_prev_output</a>;
<a name="l00118"></a><a class="code" href="classgri__iir.html#aac5a985051761be98d5753f5a1542003">00118</a> <a class="code" href="classstd_1_1vector.html">std::vector<i_type></a> <a class="code" href="classgri__iir.html#aac5a985051761be98d5753f5a1542003">d_prev_input</a>;
<a name="l00119"></a>00119 };
<a name="l00120"></a>00120
<a name="l00121"></a>00121
<a name="l00122"></a>00122 <span class="comment">//</span>
<a name="l00123"></a>00123 <span class="comment">// general case. We may want to specialize this</span>
<a name="l00124"></a>00124 <span class="comment">//</span>
<a name="l00125"></a>00125 <span class="keyword">template</span><<span class="keyword">class</span> i_type, <span class="keyword">class</span> o_type, <span class="keyword">class</span> tap_type>
<a name="l00126"></a>00126 o_type
<a name="l00127"></a><a class="code" href="classgri__iir.html#adb60d3d25c5fce9278d8f2cd5e3c74cb">00127</a> <a class="code" href="classgri__iir.html#adb60d3d25c5fce9278d8f2cd5e3c74cb" title="compute a single output value.">gri_iir<i_type, o_type, tap_type>::filter</a> (<span class="keyword">const</span> i_type input)
<a name="l00128"></a>00128 {
<a name="l00129"></a>00129 tap_type acc;
<a name="l00130"></a>00130 <span class="keywordtype">unsigned</span> i = 0;
<a name="l00131"></a>00131 <span class="keywordtype">unsigned</span> n = ntaps_ff ();
<a name="l00132"></a>00132 <span class="keywordtype">unsigned</span> m = ntaps_fb ();
<a name="l00133"></a>00133
<a name="l00134"></a>00134 <span class="keywordflow">if</span> (n == 0)
<a name="l00135"></a>00135 <span class="keywordflow">return</span> (o_type) 0;
<a name="l00136"></a>00136
<a name="l00137"></a>00137 <span class="keywordtype">int</span> latest_n = d_latest_n;
<a name="l00138"></a>00138 <span class="keywordtype">int</span> latest_m = d_latest_m;
<a name="l00139"></a>00139
<a name="l00140"></a>00140 acc = d_fftaps[0] * input;
<a name="l00141"></a>00141 <span class="keywordflow">for</span> (i = 1; i < n; i ++)
<a name="l00142"></a>00142 acc += (d_fftaps[i] * d_prev_input[latest_n + i]);
<a name="l00143"></a>00143 <span class="keywordflow">for</span> (i = 1; i < m; i ++)
<a name="l00144"></a>00144 acc += (d_fbtaps[i] * d_prev_output[latest_m + i]);
<a name="l00145"></a>00145
<a name="l00146"></a>00146 <span class="comment">// store the values twice to avoid having to handle wrap-around in the loop</span>
<a name="l00147"></a>00147 d_prev_output[latest_m] = acc;
<a name="l00148"></a>00148 d_prev_output[latest_m+m] = acc;
<a name="l00149"></a>00149 d_prev_input[latest_n] = input;
<a name="l00150"></a>00150 d_prev_input[latest_n+n] = input;
<a name="l00151"></a>00151
<a name="l00152"></a>00152 latest_n--;
<a name="l00153"></a>00153 latest_m--;
<a name="l00154"></a>00154 <span class="keywordflow">if</span> (latest_n < 0)
<a name="l00155"></a>00155 latest_n += n;
<a name="l00156"></a>00156 <span class="keywordflow">if</span> (latest_m < 0)
<a name="l00157"></a>00157 latest_m += m;
<a name="l00158"></a>00158
<a name="l00159"></a>00159 d_latest_m = latest_m;
<a name="l00160"></a>00160 d_latest_n = latest_n;
<a name="l00161"></a>00161 <span class="keywordflow">return</span> (o_type) acc;
<a name="l00162"></a>00162 }
<a name="l00163"></a>00163
<a name="l00164"></a>00164
<a name="l00165"></a>00165 <span class="keyword">template</span><<span class="keyword">class</span> i_type, <span class="keyword">class</span> o_type, <span class="keyword">class</span> tap_type>
<a name="l00166"></a>00166 <span class="keywordtype">void</span>
<a name="l00167"></a><a class="code" href="classgri__iir.html#aef452a0ffbc9d9040b08d58d0bbe0589">00167</a> <a class="code" href="classgri__iir.html#aef452a0ffbc9d9040b08d58d0bbe0589" title="compute an array of N output values. input must have N valid entries.">gri_iir<i_type, o_type, tap_type>::filter_n</a> (o_type output[],
<a name="l00168"></a>00168 <span class="keyword">const</span> i_type input[],
<a name="l00169"></a>00169 <span class="keywordtype">long</span> n)
<a name="l00170"></a>00170 {
<a name="l00171"></a>00171 <span class="keywordflow">for</span> (<span class="keywordtype">int</span> i = 0; i < n; i++)
<a name="l00172"></a>00172 output[i] = filter (input[i]);
<a name="l00173"></a>00173 }
<a name="l00174"></a>00174
<a name="l00175"></a>00175 <span class="preprocessor">#endif </span><span class="comment">/* INCLUDED_GRI_IIR_H */</span>
<a name="l00176"></a>00176
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