class SPCore::FlatTopWindow

Produces a flat top window of a given size (number of samples). A flat top window is a partially negative-valued window that has a flat top in the frequency domain. They are designed to have a broader bandwidth and so have a poorer frequency resolution, leading to low amplitude measurement error suitable for use in in spectrum analyzers for the measurement of amplitudes of sinusoidal frequency components For more info, see en.wikipedia.org/wiki/Window_function#Flat_top_window.

Attributes

data[R]

Public Class Methods

new(size) click to toggle source
# File lib/spcore/windows/flat_top_window.rb, line 11
def initialize size
  @data = Array.new(size)
  a0, a1, a2, a3, a4 = 1.0, 1.93, 1.29, 0.388, 0.032
  
  size.times do |n|
    @data[n] = a0 - a1 * Math::cos((TWO_PI * n)/(size - 1)) + a2 * Math::cos((FOUR_PI * n)/(size - 1)) - a3 * Math::cos((SIX_PI * n)/(size - 1)) + a4 * Math::cos((EIGHT_PI * n)/(size - 1))
  end
  
  max = @data.max
  
  # normalize to max of 1.0
  @data.each_index do |i|
    @data[i] /= max
  end
end