Class: Digiproc::LowpassFilter

Inherits:
DigitalFilter show all
Defined in:
lib/filters/lowpass_filter.rb

Overview

Creates a Lowpass filter via the windowing method

Constant Summary

Constants inherited from DigitalFilter

DigitalFilter::PI

Instance Attribute Summary collapse

Attributes inherited from DigitalFilter

#fft, #size, #weights, #window

Instance Method Summary collapse

Methods inherited from DigitalFilter

#calculate_ideal, #set_fft_size, #to_ds

Constructor Details

#initialize(size:, window: RectangularWindow, wc:, correct: true) ⇒ LowpassFilter

Inputs

size
Integer

number of datapoints window should be

window
Digiproc::WindowStrategy

desired window strategy

wo
Float

center frequency in radians

bw
Float

bandwidth in radians

correct
Boolean

perform frequency corrections to make frequency points more accurate. Defaults to true

Digiproc::BandpassFilter.new(size: 1000, wo: Math::PI / 4, bw: Math::PI / 10)



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# File 'lib/filters/lowpass_filter.rb', line 16

def initialize(size:, window: RectangularWindow, wc: , correct: true)
    super(size: size, window: window)
    wc = wc + @window.transition_width * PI if correct
    @equation = ->(n){ 
        n == 0 ? (wc / PI) : (Math.sin(wc * n) / (PI * n)) 
    }
    ideal_filter = calculate_ideal
    @weights = self.window.values.times ideal_filter
    @fft = Digiproc::FFT.new(time_data: self.weights)
    @fft.calculate
end

Instance Attribute Details

#equation ⇒ Object

Returns the value of attribute equation.



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# File 'lib/filters/lowpass_filter.rb', line 5

def equation
  @equation
end