Class: Digiproc::BlackmanWindow

Inherits:
WindowStrategy show all
Defined in:
lib/strategies/window/blackman_window.rb

Overview

Blackman Window Used to improve digital filters by using a non-retangular frequency domain window

Constant Summary

Constants inherited from WindowStrategy

WindowStrategy::PI

Instance Attribute Summary

Attributes inherited from WindowStrategy

#data, #equation, #size, #values

Instance Method Summary collapse

Methods inherited from WindowStrategy

#calculate, #make_odd, #to_signal

Constructor Details

#initialize(size: nil, norm_trans_freq: nil) ⇒ BlackmanWindow

Input Args

size (Optional)

Numeric (default: nil), how many datapoings the window should have

norm_trans_freq

Numeric (default: nil), the desired transition frequency

If you know what size of the the window that you need, you can input size without norm_trans_freq If you kow the desired transition frequency, the necessary size will be calculated for you based off of the window type so it is not necessary to enter the size



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# File 'lib/strategies/window/blackman_window.rb', line 13

def initialize(size: nil , norm_trans_freq: nil)
    super(size: norm_trans_freq.nil? ? size : find_size(norm_trans_freq))
    #size = @size + 2
    #@equation = lambda { |n| 0.42 - 0.5 * Math.cos(2 * PI * (n + 1) / (size - 1)) + 0.08 * Math.cos(4*PI*(n + 1) / (size - 1)) }
    @equation = lambda { |n| 0.42 - 0.5 * Math.cos(2 * PI * (n) / (size - 1)) + 0.08 * Math.cos(4*PI*(n) / (size - 1)) }
    calculate
    @values = @values.take(@size)
end

Instance Method Details

#find_size(freq) ⇒ Object

Given a freqency, return the required size of a BlackmanWindow



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# File 'lib/strategies/window/blackman_window.rb', line 23

def find_size(freq)
    size = 5.5 / freq
    make_odd(size.ceil)
end

#transition_width ⇒ Object

Return the transition width (in rad/s) based off of the size



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# File 'lib/strategies/window/blackman_window.rb', line 29

def transition_width
    5.5 / @size
end