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annotate scripts/signal/freqz_plot.m @ 7016:93c65f2a5668

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[project @ 2007-10-12 06:40:56 by jwe]
author jwe
date Fri, 12 Oct 2007 06:41:26 +0000
parents a8105a726e68
children a1dbe9d80eee
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1 ## Copyright (C) 2002 John W. Eaton
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2 ##
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3 ## This file is part of Octave.
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4 ##
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5 ## Octave is free software; you can redistribute it and/or modify it
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6 ## under the terms of the GNU General Public License as published by
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7 ## the Free Software Foundation; either version 3 of the License, or (at
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8 ## your option) any later version.
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9 ##
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10 ## Octave is distributed in the hope that it will be useful, but
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11 ## WITHOUT ANY WARRANTY; without even the implied warranty of
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12 ## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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13 ## General Public License for more details.
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14 ##
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15 ## You should have received a copy of the GNU General Public License
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16 ## along with Octave; see the file COPYING. If not, see
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17 ## <http://www.gnu.org/licenses/>.
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18
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19 ## -*- texinfo -*-
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20 ## @deftypefn {Function File} {} freqz_plot (@var{w}, @var{h})
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21 ## Plot the pass band, stop band and phase response of @var{h}.
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22 ## @end deftypefn
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23
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24 ## Author: Paul Kienzle <pkienzle@users.sf.net>
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25
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26 function freqz_plot (w, h)
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27
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28 n = length (w);
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29
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30 ## ## exclude zero-frequency
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31 ## h = h (2 : length (h));
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32 ## w = w (2 : length (w));
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33 ## n = n-1;
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34
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35 mag = 20 * log10 (abs (h));
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36 phase = unwrap (arg (h));
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37 maxmag = max (mag);
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38
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39 subplot (3, 1, 1);
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40 plot (w, mag);
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41 grid ("on");
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42 legend("Pass band (dB)");
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43 axis ([w(1), w(n), maxmag-3, maxmag], "labely");
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44
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45 subplot (3, 1, 2);
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46 plot (w, mag);
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47 grid ("on");
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48 legend ("Stop band (dB)");
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49 if (maxmag - min (mag) > 100)
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50 axis ([w(1), w(n), maxmag-100, maxmag], "labely");
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51 else
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52 axis ("autoy", "labely");
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53 endif
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54
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55 subplot (3, 1, 3);
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56 plot (w, phase*360/(2*pi));
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57 grid ("on");
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58 legend ("Phase (degrees)");
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59 xlabel ("Frequency");
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60 axis ([w(1), w(n)], "autoy", "label");
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61
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62 endfunction