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/***********************************************/
/**
* @file DigitalFilterNotch.cpp
*
* Implemented after Sophocles J. Orfanidis, "Introduction To Signal Processing", 2009.
*
* @brief Notch filter.
*
* @author Andreas Kvas
* @date 2017-02-07
*
*/
/***********************************************/
#include "base/import.h"
#include "base/fourier.h"
#include "classes/digitalFilter/digitalFilterNotch.h"
#include "files/fileMatrix.h"
/***********************************************/
DigitalFilterNotch::DigitalFilterNotch(Config& config)
{
try
{
Double w0; // normalized notch frequency
Double bw; // bandwidth at -3db
readConfig(config, "notchFrequency", w0, Config::MUSTSET, "", "normalized notch frequency w_n = (f_n/f_nyq)");
readConfig(config, "bandWidth", bw, Config::MUSTSET, "", "bandwidth at -3db. Quality factor of filter Q = w_n/bw");
readConfig(config, "backwardDirection", backward, Config::DEFAULT, "0", "apply filter in backward direction");
readConfig(config, "inFrequencyDomain", inFrequencyDomain, Config::DEFAULT, "0", "apply filter in frequency domain");
readConfig(config, "padType", padType, Config::MUSTSET, "", "");
if(isCreateSchema(config)) return;
w0 *= PI;
bw *= PI;
Double gb = 1/std::sqrt(2); // |H(w)|^2 = 1/2, p. 575 11.3.1
Double beta = (std::sqrt(1.0-gb*gb)/gb)*std::tan(bw/2.0); // p. 575 11.3.4
Double gain = 1.0/(1.0+beta); // p. 575 11.3.6
bn = Vector(3, gain);
bn(1) = -2.0*std::cos(w0)*gain; // bn = gain*[1.0, -2*cos(w0), 1.0], p. 575 11.3.7
bnStartIndex = 0;
an = Vector(3, 1.0);
an(1) = -2.0*gain*std::cos(w0);
an(2) = 2.0*gain-1.0; // an = [1.0, -2*gain*cos(w0), 2*gain-1.0], p. 575 11.3.7
}
catch(std::exception &e)
{
GROOPS_RETHROW(e)
}
}
/***********************************************/
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