File:Processing gain comparison (Hann vs Blackman).gif

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Processing_gain_comparison_(Hann_vs_Blackman).gif ‎(647 × 518 pixels, file size: 16 KB, MIME type: image/gif)

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Description
English: This figure compares the processing gain of two window functions for sinusoidal inputs, with both minimum and maximum scalloping loss.
Date
Source Own work
Author Bob K
Permission
(Reusing this file)
I, the copyright holder of this work, hereby publish it under the following license:
Creative Commons CC-Zero This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication.
The person who associated a work with this deed has dedicated the work to the public domain by waiving all of their rights to the work worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.

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Derivative works of this file:

GIF development
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This GIF graphic was created with LibreOffice.
Gnu Octave Script
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This graphic was created with the help of the following script:

Octave code

graphics_toolkit gnuplot

  N = 256;                % sams_per_fft;
  window1 = hann(N)'/sum(hann(N));
  window2 = blackmanharris(N)/sum(blackmanharris(N));
%
  Fs = N;                 % sams_per_sec;
  HzPerBin = Fs/N;
  F1 = -20.0*HzPerBin;    % bin -20
  F2 = +20.5*HzPerBin;    % bin 20.5
%
  L = 100000;
  n = 1:L;
  x = exp(j*2*pi*F1/Fs*n) + exp(j*2*pi*F2/Fs*n);
  x = x + (randn(1,L) +j*randn(1,L))*1.4;
%
  sams_per_offset = 0.75*N;    % overlap = 25%
%
% number of samples available beyond just one FFT
  excess_sams = length(x) - N;
%
  j1 = floor( excess_sams / sams_per_offset );
  sams_per_offset = floor( excess_sams / j1 );
  num_ffts = 1 + j1;
%
% define the first block of data
  samples = 1:N;
%
  amplitude1 = zeros(1,N);
  amplitude2 = zeros(1,N);
%
% Loop over all the available blocks
  for j1 = 1 : num_ffts
    amplitude1 = amplitude1 + abs(fft( x(samples) .* window1 ));
    amplitude2 = amplitude2 + abs(fft( x(samples) .* window2 ));
    samples = samples + sams_per_offset;
  end
%
  amplitude1  = 20*log10(fftshift(amplitude1/num_ffts));
  amplitude2  = 20*log10(fftshift(amplitude2/num_ffts));
% 
  abscissa = -40:40;
  figure
  set(gca,'FontSize',8)
  subplot(2,1,1);
  h = area(abscissa, amplitude1(abscissa +N/2+1), ...
  'FaceColor', [.871 .49 0], 'edgecolor', [.871 .49 0])
  set(h,'BaseValue',-20)
  xlim([-40 40])
  ylim([-20 2])
  set(gca,'XTick', [ ])
  set(gca,'YGrid','on')
  ylabel('decibels')
  title('Hann');
%
  subplot(2,1,2);
  h = area(abscissa, amplitude2(abscissa +N/2+1), ...
  'FaceColor', [.871 .49 0], 'edgecolor', [.871 .49 0])
  set(h,'BaseValue',-20)
  xlim([-40 40])
  ylim([-20 2])
  set(gca,'XTick', [ ])
  set(gca,'YGrid','on')
  ylabel('decibels')
  title('Blackman-Harris');

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Date/TimeThumbnailDimensionsUserComment
current01:02, 25 February 2013Thumbnail for version as of 01:02, 25 February 2013647 × 518 (16 KB)Bob K (talk | contribs)User created page with UploadWizard

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