///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2018 F4EXB //
// written by Edouard Griffiths //
// //
// See: http://liquidsdr.org/blog/pll-howto/ //
// Fixed filter registers saturation //
// Added order for PSK locking. This brilliant idea actually comes from this //
// post: https://www.dsprelated.com/showthread/comp.dsp/36356-1.php //
// //
// 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 //
// //
// 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 . //
///////////////////////////////////////////////////////////////////////////////////
#include
#include
#include "phaselockcomplex.h"
PhaseLockComplex::PhaseLockComplex() :
m_a1(1.0),
m_a2(1.0),
m_b0(1.0),
m_b1(1.0),
m_b2(1.0),
m_v0(0.0),
m_v1(0.0),
m_v2(0.0),
m_deltaPhi(0.0),
m_phiHat(0.0),
m_phiHatPrev(0.0),
m_phiHat1(0.0),
m_phiHat2(0.0),
m_dPhiHatAccum(0.0),
m_phiHatCount(0),
m_y(1.0, 0.0),
m_p(1.0, 0.0),
m_yRe(1.0),
m_yIm(0.0),
m_freq(0.0),
m_freqPrev(0.0),
m_lock(0.0),
m_lockCount(0),
m_pskOrder(1),
m_lockTime1(480),
m_lockTime(2400),
m_lockTimef(2400.0f),
m_lockThreshold(4.8f),
m_avgF(2400)
{
}
void PhaseLockComplex::computeCoefficients(Real wn, Real zeta, Real K)
{
double t1 = K/(wn*wn); //
double t2 = 2*zeta/wn - 1/K; //
double b0 = 2*K*(1.+t2/2.0f);
double b1 = 2*K*2.;
double b2 = 2*K*(1.-t2/2.0f);
double a0 = 1 + t1/2.0f;
double a1 = -t1;
double a2 = -1 + t1/2.0f;
qDebug("PhaseLockComplex::computeCoefficients: b_raw: %f %f %f", b0, b1, b2);
qDebug("PhaseLockComplex::computeCoefficients: a_raw: %f %f %f", a0, a1, a2);
m_b0 = b0 / a0;
m_b1 = b1 / a0;
m_b2 = b2 / a0;
// a0 = 1.0 is implied
m_a1 = a1 / a0;
m_a2 = a2 / a0;
qDebug("PhaseLockComplex::computeCoefficients: b: %f %f %f", m_b0, m_b1, m_b2);
qDebug("PhaseLockComplex::computeCoefficients: a: 1.0 %f %f", m_a1, m_a2);
reset();
}
void PhaseLockComplex::setPskOrder(unsigned int order)
{
m_pskOrder = order > 0 ? order : 1;
reset();
}
void PhaseLockComplex::setSampleRate(unsigned int sampleRate)
{
m_lockTime1 = sampleRate / 100; // 10ms for order 1
m_lockTime = sampleRate / 20; // 50ms for order > 1
m_lockTimef = (float) m_lockTime;
m_lockThreshold = m_lockTime * 0.00015f; // threshold of 0.002 taking division by lock time into account
m_avgF.resize(m_lockTime);
reset();
}
void PhaseLockComplex::reset()
{
// reset filter accumulators and phase
m_v0 = 0.0f;
m_v1 = 0.0f;
m_v2 = 0.0f;
m_deltaPhi = 0.0f;
m_phiHat = 0.0f;
m_phiHatPrev = 0.0f;
m_phiHat1 = 0.0f;
m_phiHat2 = 0.0f;
m_dPhiHatAccum = 0.0f;
m_phiHatCount = 0;
m_y.real(1.0);
m_y.imag(0.0);
m_p.real(1.0);
m_p.imag(0.0);
m_yRe = 1.0f;
m_yIm = 0.0f;
m_freq = 0.0f;
m_freqPrev = 0.0f;
m_lock = 0.0f;
m_lockCount = 0;
}
void PhaseLockComplex::feed(float re, float im)
{
m_yRe = cos(m_phiHat);
m_yIm = sin(m_phiHat);
m_y.real(m_yRe);
m_y.imag(m_yIm);
std::complex x(re, im);
m_deltaPhi = std::arg(x * std::conj(m_y));
// bring phase 0 on any of the PSK symbols
if (m_pskOrder > 1) {
m_deltaPhi = normalizeAngle(m_pskOrder*m_deltaPhi);
}
// advance buffer
m_v2 = m_v1; // shift center register to upper register
m_v1 = m_v0; // shift lower register to center register
// compute new lower register
m_v0 = m_deltaPhi - m_v1*m_a1 - m_v2*m_a2;
// compute new output
m_phiHat = m_v0*m_b0 + m_v1*m_b1 + m_v2*m_b2;
// prevent saturation
if (m_phiHat > 2.0*M_PI)
{
m_v0 *= (m_phiHat - 2.0*M_PI) / m_phiHat;
m_v1 *= (m_phiHat - 2.0*M_PI) / m_phiHat;
m_v2 *= (m_phiHat - 2.0*M_PI) / m_phiHat;
m_phiHat -= 2.0*M_PI;
}
if (m_phiHat < -2.0*M_PI)
{
m_v0 *= (m_phiHat + 2.0*M_PI) / m_phiHat;
m_v1 *= (m_phiHat + 2.0*M_PI) / m_phiHat;
m_v2 *= (m_phiHat + 2.0*M_PI) / m_phiHat;
m_phiHat += 2.0*M_PI;
}
// lock estimation
if (m_pskOrder > 1)
{
float dPhi = normalizeAngle(m_phiHat - m_phiHatPrev);
m_avgF(dPhi);
if (m_phiHatCount < (m_lockTime-1))
{
m_phiHatCount++;
}
else
{
m_freq = m_avgF.asFloat();
float dFreq = m_freq - m_freqPrev;
if ((dFreq > -m_lockThreshold) && (dFreq < m_lockThreshold))
{
if (m_lockCount < 20) {
m_lockCount++;
}
}
else{
if (m_lockCount > 0) {
m_lockCount--;
}
}
m_freqPrev = m_freq;
m_phiHatCount = 0;
}
// if (m_phiHatCount < (m_lockTime-1))
// {
// m_dPhiHatAccum += dPhi; // re-accumulate phase for differential calculation
// m_phiHatCount++;
// }
// else
// {
// float dPhi11 = (m_dPhiHatAccum - m_phiHat1); // optimized out division by lock time
// float dPhi12 = (m_phiHat1 - m_phiHat2);
// m_lock = dPhi11 - dPhi12; // second derivative of phase to get lock status
// if ((m_lock > -m_lockThreshold) && (m_lock < m_lockThreshold)) // includes re-multiplication by lock time
// {
// if (m_lockCount < 20) { // [0..20]
// m_lockCount++;
// }
// }
// else
// {
// if (m_lockCount > 0) {
// m_lockCount -= 2;
// }
// }
// m_phiHat2 = m_phiHat1;
// m_phiHat1 = m_dPhiHatAccum;
// m_dPhiHatAccum = 0.0f;
// m_phiHatCount = 0;
// }
// m_phiHatPrev = m_phiHat;
}
else
{
m_freq = (m_phiHat - m_phiHatPrev) / (2.0*M_PI);
if (m_freq < -1.0f) {
m_freq += 2.0f;
} else if (m_freq > 1.0f) {
m_freq -= 2.0f;
}
float dFreq = m_freq - m_freqPrev;
if ((dFreq > -0.01) && (dFreq < 0.01))
{
if (m_lockCount < (m_lockTime1-1)) { // [0..479]
m_lockCount++;
}
}
else
{
m_lockCount = 0;
}
m_phiHatPrev = m_phiHat;
m_freqPrev = m_freq;
}
}
float PhaseLockComplex::normalizeAngle(float angle)
{
while (angle <= -M_PI) {
angle += 2.0*M_PI;
}
while (angle > M_PI) {
angle -= 2.0*M_PI;
}
return angle;
}