mirror of https://github.com/f4exb/sdrangel.git
138 lines
4.2 KiB
C++
138 lines
4.2 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2018 F4EXB //
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// written by Edouard Griffiths //
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// //
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// See: http://liquidsdr.org/blog/pll-howto/ //
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// Fixes filter registers saturation //
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// //
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// This program is free software; you can redistribute it and/or modify //
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// it under the terms of the GNU General Public License as published by //
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// the Free Software Foundation as version 3 of the License, or //
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// //
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// This program is distributed in the hope that it will be useful, //
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// but WITHOUT ANY WARRANTY; without even the implied warranty of //
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
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// GNU General Public License V3 for more details. //
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// //
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// You should have received a copy of the GNU General Public License //
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// along with this program. If not, see <http://www.gnu.org/licenses/>. //
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///////////////////////////////////////////////////////////////////////////////////
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#include <complex.h>
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#include <math.h>
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#include "phaselockcomplex.h"
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PhaseLockComplex::PhaseLockComplex() :
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m_a1(1.0),
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m_a2(1.0),
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m_b0(1.0),
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m_b1(1.0),
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m_b2(1.0),
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m_v0(0.0),
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m_v1(0.0),
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m_v2(0.0),
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m_deltaPhi(0.0),
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m_phiHatLast(0.0),
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m_phiHat(0.0),
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m_y(1.0, 0.0),
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m_yRe(1.0),
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m_yIm(0.0),
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m_freq(0.0)
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{
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}
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void PhaseLockComplex::computeCoefficients(Real wn, Real zeta, Real K)
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{
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double t1 = K/(wn*wn); //
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double t2 = 2*zeta/wn - 1/K; //
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double b0 = 2*K*(1.+t2/2.0f);
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double b1 = 2*K*2.;
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double b2 = 2*K*(1.-t2/2.0f);
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double a0 = 1 + t1/2.0f;
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double a1 = -t1;
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double a2 = -1 + t1/2.0f;
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qDebug("PhaseLockComplex::computeCoefficients: b_raw: %f %f %f", b0, b1, b2);
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qDebug("PhaseLockComplex::computeCoefficients: a_raw: %f %f %f", a0, a1, a2);
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m_b0 = b0 / a0;
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m_b1 = b1 / a0;
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m_b2 = b2 / a0;
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// a0 = 1.0 is implied
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m_a1 = a1 / a0;
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m_a2 = a2 / a0;
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qDebug("PhaseLockComplex::computeCoefficients: b: %f %f %f", m_b0, m_b1, m_b2);
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qDebug("PhaseLockComplex::computeCoefficients: a: 1.0 %f %f", m_a1, m_a2);
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reset();
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}
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void PhaseLockComplex::reset()
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{
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// reset filter accumulators and phase
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m_v0 = 0.0f;
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m_v1 = 0.0f;
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m_v2 = 0.0f;
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m_deltaPhi = 0.0f;
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m_phiHatLast = 0.0f;
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m_phiHat = 0.0f;
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m_y.real(1.0);
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m_y.real(0.0);
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m_yRe = 1.0f;
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m_yIm = 0.0f;
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m_freq = 0.0f;
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}
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void PhaseLockComplex::feed(float re, float im)
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{
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m_yRe = cos(m_phiHat);
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m_yIm = sin(m_phiHat);
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m_y.real(m_yRe);
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m_y.imag(m_yIm);
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std::complex<float> x(re, im);
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m_deltaPhi = std::arg(x * std::conj(m_y));
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// advance buffer
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m_v2 = m_v1; // shift center register to upper register
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m_v1 = m_v0; // shift lower register to center register
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// compute new lower register
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m_v0 = m_deltaPhi - m_v1*m_a1 - m_v2*m_a2;
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// compute new output
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m_phiHat = m_v0*m_b0 + m_v1*m_b1 + m_v2*m_b2;
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// prevent saturation
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if (m_phiHat > 2.0*M_PI)
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{
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m_v0 *= (m_phiHat - 2.0*M_PI) / m_phiHat;
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m_v1 *= (m_phiHat - 2.0*M_PI) / m_phiHat;
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m_v2 *= (m_phiHat - 2.0*M_PI) / m_phiHat;
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m_phiHat -= 2.0*M_PI;
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}
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if (m_phiHat < -2.0*M_PI)
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{
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m_v0 *= (m_phiHat + 2.0*M_PI) / m_phiHat;
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m_v1 *= (m_phiHat + 2.0*M_PI) / m_phiHat;
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m_v2 *= (m_phiHat + 2.0*M_PI) / m_phiHat;
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m_phiHat += 2.0*M_PI;
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}
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m_freq = (m_phiHat - m_phiHatLast) / (2.0*M_PI);
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if (m_freq < -1.0f) {
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m_freq += 2.0f;
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} else if (m_freq > 1.0f) {
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m_freq -= 2.0f;
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}
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m_phiHatLast = m_phiHat;
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}
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