makebwhite

----- MakeWNB:  This script generates a Gaussian-modulated 
      burst of noise which is white over a specified frequency 
      band.

 -- Patrick Sutton & Sam Finn 2004.08.28

0001 function x = makebwhite(fc, df, dt, fs, T)
0002 
0003 %----- MakeWNB:  This script generates a Gaussian-modulated
0004 %      burst of noise which is white over a specified frequency
0005 %      band.
0006 %
0007 % -- Patrick Sutton & Sam Finn 2004.08.28
0008 
0009 % $Id: makebwhite.m,v 1.1 2005/05/11 19:39:16 stuver Exp $
0010 
0011 
0012 %-----------------------------------------------
0013 % User-specified quantities.
0014 %-----------------------------------------------
0015 
0016 %----- Set desired time-frequency properties:
0017 % fc = 1000;  % central frequency
0018 % df = 100;   % bandwidth
0019 % dt = 0.001; % duration
0020 % fs = 16384; % sampling rate
0021 % T = 1;      % duration of data sample
0022 
0023 
0024 %-----------------------------------------------
0025 % Do not edit below this line.
0026 %-----------------------------------------------
0027 
0028 %----- Generate noise with the desired frequency content:
0029 
0030 %----- Generate white noise burst with duration dt at sample rate df
0031 %      (white over entire band [-df/2,df/2]).
0032 nSamp = ceil(T*df);
0033 x = randn([1,nSamp]);
0034 
0035 %----- Resample to sample rate fSamp
0036 [p,q] = rat(fs/df);
0037 x = resample(x,p,q);
0038 
0039 %----- Truncate (if necessary) to duration dt
0040 nSamp = floor(T*fs);
0041 x = x(1:nSamp);
0042 
0043 %----- Heterodyne up by f+df/2 (moves zero frequency to center of desired
0044 %      band)
0045 fup = fc+df/2;
0046 x = x.*exp(-2*pi*i*fup/fs*(1:numel(x)));
0047 
0048 %----- Take real part and adjust amplitude
0049 x = real(x)/sqrt(2);
0050 
0051 %----- window in the time domain
0052 t = [0:1/fs:T-1/fs]';
0053 env = exp(-(t-T/2).^2/2/dt.^2);
0054 x = env.*x';