mirror of
https://github.com/f4exb/sdrangel.git
synced 2025-10-29 20:10:22 -04:00
113 lines
3.6 KiB
C++
113 lines
3.6 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
|
|
// Copyright (C) 2021 Jon Beniston, M7RCE <jon@beniston.com> //
|
|
// Copyright 2006-2021 Free Software Foundation, Inc. //
|
|
// Copyright (C) 2018 Edouard Griffiths, F4EXB //
|
|
// //
|
|
// Based on the Costas Loop from GNU Radio //
|
|
// //
|
|
// 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 "costasloop.h"
|
|
#include <cmath>
|
|
|
|
// Loop bandwidth supposedly ~ 2pi/100 rads/sample
|
|
// pskOrder 2, 4 or 8
|
|
CostasLoop::CostasLoop(float loopBW, unsigned int pskOrder) :
|
|
m_maxFreq(1.0f),
|
|
m_minFreq(-1.0f),
|
|
m_pskOrder(pskOrder)
|
|
{
|
|
computeCoefficients(loopBW);
|
|
reset();
|
|
}
|
|
|
|
CostasLoop::~CostasLoop()
|
|
{
|
|
}
|
|
|
|
void CostasLoop::reset()
|
|
{
|
|
m_y.real(1.0f);
|
|
m_y.imag(0.0f);
|
|
m_freq = 0.0f;
|
|
m_phase = 0.0f;
|
|
m_freq = 0.0f;
|
|
m_error = 0.0f;
|
|
}
|
|
|
|
// 2nd order loop with critical damping
|
|
void CostasLoop::computeCoefficients(float loopBW)
|
|
{
|
|
float damping = sqrtf(2.0f) / 2.0f;
|
|
float denom = (1.0 + 2.0 * damping * loopBW + loopBW * loopBW);
|
|
m_alpha = (4 * damping * loopBW) / denom;
|
|
m_beta = (4 * loopBW * loopBW) / denom;
|
|
}
|
|
|
|
void CostasLoop::setSampleRate(unsigned int sampleRate)
|
|
{
|
|
(void) sampleRate;
|
|
|
|
reset();
|
|
}
|
|
|
|
static float branchlessClip(float x, float clip)
|
|
{
|
|
return 0.5f * (std::abs(x + clip) - std::abs(x - clip));
|
|
}
|
|
|
|
// Don't use built-in complex.h multiply to avoid NaN/INF checking
|
|
static void fastComplexMultiply(std::complex<float> &out, const std::complex<float> cc1, const std::complex<float> cc2)
|
|
{
|
|
float o_r, o_i;
|
|
|
|
o_r = (cc1.real() * cc2.real()) - (cc1.imag() * cc2.imag());
|
|
o_i = (cc1.real() * cc2.imag()) + (cc1.imag() * cc2.real());
|
|
|
|
out.real(o_r);
|
|
out.imag(o_i);
|
|
}
|
|
|
|
void CostasLoop::feed(float re, float im)
|
|
{
|
|
std::complex<float> nco(::cosf(-m_phase), ::sinf(-m_phase));
|
|
|
|
std::complex<float> in, out;
|
|
in.real(re);
|
|
in.imag(im);
|
|
fastComplexMultiply(out, in, nco);
|
|
|
|
switch (m_pskOrder)
|
|
{
|
|
case 2:
|
|
m_error = phaseDetector2(out);
|
|
break;
|
|
case 4:
|
|
m_error = phaseDetector4(out);
|
|
break;
|
|
case 8:
|
|
m_error = phaseDetector8(out);
|
|
break;
|
|
}
|
|
m_error = branchlessClip(m_error, 1.0f);
|
|
|
|
advanceLoop(m_error);
|
|
phaseWrap();
|
|
frequencyLimit();
|
|
|
|
m_y.real(-nco.real());
|
|
m_y.imag(nco.imag());
|
|
}
|