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Contents
##
# Creates a bandstop filter via the Windowing Method
class Digiproc::BandstopFilter < Digiproc::DigitalFilter
attr_accessor :equation
##
# == 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)
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
end
Version data entries
7 entries across 7 versions & 1 rubygems