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sdrangel/sdrbase/dsp/goertzel.cpp

75 lines
2.5 KiB
C++

///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2012 maintech GmbH, Otto-Hahn-Str. 15, 97204 Hoechberg, Germany //
// written by Christian Daniel //
// Copyright (C) 2015-2019 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
// Copyright (C) 2020 Jon Beniston, M7RCE <jon@beniston.com> //
// //
// This program is free software; you can redistribute it and/or modify //
// it under the terms of the GNU General Public License as published by //
// the Free Software Foundation as version 3 of the License, or //
// (at your option) any later version. //
// //
// This program is distributed in the hope that it will be useful, //
// but WITHOUT ANY WARRANTY; without even the implied warranty of //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
// GNU General Public License V3 for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
///////////////////////////////////////////////////////////////////////////////////
#include "goertzel.h"
Goertzel::Goertzel(double frequency, int sampleRate) :
m_s0(0.0),
m_s1(0.0),
m_s2(0.0),
m_z(0.0),
m_sampleCount(0)
{
m_a = 2.0 * M_PI * frequency / sampleRate;
m_b = 2.0 * cos(m_a);
m_c = std::complex<double>(cos(-m_a), sin(-m_a));
}
void Goertzel::reset()
{
m_s0 = 0.0;
m_s1 = 0.0;
m_s2 = 0.0;
m_z = 0.0;
m_sampleCount = 0;
}
void Goertzel::filter(double sample)
{
m_s0 = m_b * m_s1 - m_s2 + sample;
m_s2 = m_s1;
m_s1 = m_s0;
m_sampleCount++;
}
std::complex<double> Goertzel::goertzel(double lastSample)
{
m_s0 = m_b * m_s1 - m_s2 + lastSample;
m_sampleCount++;
std::complex<double> y = m_s0 - m_s1 * m_c;
double x = -m_a * (m_sampleCount - 1.0);
std::complex<double> d(cos(x), sin(x));
double scale = m_sampleCount / 2.0;
m_z = y * d / scale;
return m_z;
}
double Goertzel::mag()
{
return std::abs(m_z);
}
double Goertzel::phase()
{
return std::arg(m_z);
}