Class: Digiproc::BandstopFilter

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

Overview

Creates a bandstop 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, wo: nil, bw: nil, wlp_upper: nil, whp_lower: nil, correct: true) ⇒ BandstopFilter

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

wlp_upper
Float

Upper frequency limit (radians) of the lowpass passband

whp_lower
Float

Lower frequency limit (radians) of the highpass passband

correct
Boolean

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

Must have either ‘wo` and `bw` or `wlp_upper` and `whp_lower` For wo and bw, include the “don’t care” areas in the bandstop area

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



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# File 'lib/filters/bandstop_filter.rb', line 22

def initialize(size:, window: RectangularWindow, wo: nil, bw: nil, wlp_upper: nil , whp_lower: nil, correct: true )

    super(size: size, window: window)
    
    if !!wo && !!bw
        bw += (@window.transition_width * 2 * PI)
        wlp_upper = wo - bw / 2.0
        whp_lower = wo + bw / 2.0
    else
        raise ArgumentError.new("You must provide either bandwidth and center freq or frequency bands") if wlp_upper.nil? or whp_lower.nil? 
        wlp_upper += @window.transition_width * PI if correct
        whp_lower -= @window.transition_width * PI if correct
    end
    
    @equation = ->(n){ 
        n == 0 ?  (wlp_upper / PI) + (( PI - whp_lower )/ PI ) : ((Math.sin(wlp_upper * n) - Math.sin(whp_lower * n)) / (PI * n))
    }
    ideal_filter = calculate_ideal
    @weights = self.window.values.times ideal_filter
    @fft = FFT.new(data: self.weights)
    @fft.calculate
end

Instance Attribute Details

#equation ⇒ Object

Returns the value of attribute equation.



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# File 'lib/filters/bandstop_filter.rb', line 6

def equation
  @equation
end