class Digiproc::BandstopFilter

Creates a bandstop filter via the Windowing Method

Attributes

equation[RW]

Public Class Methods

new(size:, window: RectangularWindow, wo: nil, bw: nil, wlp_upper: nil , whp_lower: nil, correct: true ) click to toggle source

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)
Calls superclass method Digiproc::DigitalFilter::new
# 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