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annotate m-toolbox/classes/+utils/@math/blwhitenoise.m @ 0:f0afece42f48

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Import.
author Daniele Nicolodi <nicolodi@science.unitn.it>
date Wed, 23 Nov 2011 19:22:13 +0100
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Daniele Nicolodi <nicolodi@science.unitn.it>
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1 % BLWHITENOISE return a band limited gaussian distributed white noise
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Daniele Nicolodi <nicolodi@science.unitn.it>
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2 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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3 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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4 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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5 % DESCRIPTION: BLWHITENOISE return a band limited Gaussian distributed
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Daniele Nicolodi <nicolodi@science.unitn.it>
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6 % white noise
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Daniele Nicolodi <nicolodi@science.unitn.it>
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7 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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8 % CALL: wn = blwhitenoise()
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Daniele Nicolodi <nicolodi@science.unitn.it>
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9 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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10 % INPUTS: npts - number of data points in the series. Note, number of
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Daniele Nicolodi <nicolodi@science.unitn.it>
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11 % seconds is npts*fs
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Daniele Nicolodi <nicolodi@science.unitn.it>
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12 % fs - sampling frequency
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Daniele Nicolodi <nicolodi@science.unitn.it>
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13 % fl - lower bandwidth frequency
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Daniele Nicolodi <nicolodi@science.unitn.it>
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14 % fh - higher bandwidth frequency
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15 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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16 % OUTPUTS: wn - band limited gaussian white noise
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17 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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18 % REFERENCES:
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Daniele Nicolodi <nicolodi@science.unitn.it>
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19 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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20 % [1] Kafadar, K., Gaussian white-noise generation for digital signal
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Daniele Nicolodi <nicolodi@science.unitn.it>
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21 % synthesis. IEEE Transactions on Instrumentation and Measurement IM-35(4),
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Daniele Nicolodi <nicolodi@science.unitn.it>
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22 % 492-495, 1986.
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23 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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24 % VERSION: $Id: rand.m,v 1.2 2008/10/24 06:19:23 hewitson Exp $
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25 %
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Daniele Nicolodi <nicolodi@science.unitn.it>
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26 % HISTORY: 04-01-2010 Luigi Ferraioli
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Daniele Nicolodi <nicolodi@science.unitn.it>
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27 % Creation
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Daniele Nicolodi <nicolodi@science.unitn.it>
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28 %
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29 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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30
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Daniele Nicolodi <nicolodi@science.unitn.it>
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31 function Xt = blwhitenoise(npts,fs,fl,fh)
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32
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33 % generate linear spaced frequency vactor for fft
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Daniele Nicolodi <nicolodi@science.unitn.it>
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34 f = (0:floor(npts/2)).*fs./npts;
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Daniele Nicolodi <nicolodi@science.unitn.it>
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35 f = f';
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Daniele Nicolodi <nicolodi@science.unitn.it>
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36 nf = length(f);
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37
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Daniele Nicolodi <nicolodi@science.unitn.it>
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38 % amplitude vector
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Daniele Nicolodi <nicolodi@science.unitn.it>
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39 amp = zeros(nf,1);
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40
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Daniele Nicolodi <nicolodi@science.unitn.it>
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41 % phase vactor
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Daniele Nicolodi <nicolodi@science.unitn.it>
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42 phs = zeros(nf,1);
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43
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Daniele Nicolodi <nicolodi@science.unitn.it>
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44 % select frequency range
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Daniele Nicolodi <nicolodi@science.unitn.it>
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45 if fh>fs/2
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46 fh = fs/2;
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47 end
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48 if fl<0
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49 fl = 0;
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50 end
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51
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52 idxl = f>=fl;
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53 idxh = f<=fh;
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54 idx = idxl&idxh;
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Daniele Nicolodi <nicolodi@science.unitn.it>
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55 n1s = sum(idx);
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56
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57 phs(idx,1) = -pi + (2*pi).*rand(n1s,1);
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58 phs(1,1) = 0;
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59 phs(end,1) = 0;
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60 amp(idx,1) = sqrt(npts);
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61 amp(1,1) = 0;
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62 amp(end,1) = 0;
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63
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Daniele Nicolodi <nicolodi@science.unitn.it>
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64 % get final random phase and constant amplitude
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Daniele Nicolodi <nicolodi@science.unitn.it>
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65 phs = [phs;-1.*flipud(phs(2:end-1))];
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66 amp = [amp;flipud(amp(2:end-1))];
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67
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68 % fft signal
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69 Xf = amp.*(cos(phs)+1i.*sin(phs));
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70
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71 % time domain signal
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Daniele Nicolodi <nicolodi@science.unitn.it>
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72 Xt = ifft(Xf);
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73
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74 end
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75 % END
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