mirror of https://github.com/f4exb/sdrangel.git
123 lines
4.2 KiB
C++
123 lines
4.2 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
|
|
// 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 <http://www.gnu.org/licenses/>. //
|
|
///////////////////////////////////////////////////////////////////////////////////
|
|
|
|
#include "freqlockcomplex.h"
|
|
#include "IIRFilterCode.h"
|
|
|
|
FreqLockComplex::FreqLockComplex() :
|
|
m_a0(1.0),
|
|
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_y(1.0, 0.0),
|
|
m_prod(1.0, 0.0),
|
|
m_yRe(1.0),
|
|
m_yIm(0.0),
|
|
m_freq(0.0),
|
|
m_phi(0.0),
|
|
m_iir(0)
|
|
{
|
|
}
|
|
|
|
FreqLockComplex::~FreqLockComplex()
|
|
{
|
|
if (m_iir) {
|
|
delete m_iir;
|
|
}
|
|
}
|
|
|
|
void FreqLockComplex::reset()
|
|
{
|
|
m_v0 = 0.0f;
|
|
m_v1 = 0.0f;
|
|
m_v2 = 0.0f;
|
|
m_y.real(1.0);
|
|
m_y.imag(0.0);
|
|
m_prod.real(1.0);
|
|
m_prod.imag(0.0);
|
|
m_yRe = 1.0f;
|
|
m_yIm = 0.0f;
|
|
m_freq = 0.0f;
|
|
m_phi = 0.0f;
|
|
}
|
|
|
|
// wn is in terms of Nyquist. For example, if the sampling frequency = 20 kHz
|
|
// and the 3 dB corner frequency is 1.5 kHz, then OmegaC = 0.15
|
|
// i.e. 100.0 / (SR/2) or 200 / SR for 100 Hz
|
|
void FreqLockComplex::computeCoefficients(float wn)
|
|
{
|
|
kitiirfir::TIIRFilterParams params;
|
|
|
|
params.BW = 0.0; // For band pass and notch filters - unused here
|
|
params.Gamma = 0.0; // For Adjustable Gauss. - unused here
|
|
params.IIRPassType = kitiirfir::iirLPF;
|
|
params.NumPoles = 1;
|
|
params.OmegaC = wn;
|
|
params.ProtoType = kitiirfir::BUTTERWORTH;
|
|
params.Ripple = 0.0; // For Elliptic and Chebyshev - unused here
|
|
params.StopBanddB = 0.0; // For Elliptic and Inverse Chebyshev - unused here
|
|
params.dBGain = 0.0;
|
|
|
|
kitiirfir::TIIRCoeff coeff = kitiirfir::CalcIIRFilterCoeff(params);
|
|
float a[3], b[3];
|
|
|
|
a[0] = coeff.a0[0];
|
|
a[1] = coeff.a1[0];
|
|
a[2] = coeff.a2[0];
|
|
b[0] = coeff.b0[0];
|
|
b[1] = coeff.b1[0];
|
|
b[2] = coeff.b2[0];
|
|
|
|
qDebug("FreqLockComplex::computeCoefficients: b: %f %f %f", b[0], b[1], b[2]);
|
|
qDebug("FreqLockComplex::computeCoefficients: a: %f %f %f", a[0], a[1], a[2]);
|
|
|
|
m_iir = new IIRFilter<float, 2>(a, b);
|
|
}
|
|
|
|
void FreqLockComplex::feed(float re, float im)
|
|
{
|
|
m_yRe = cos(m_phi);
|
|
m_yIm = sin(m_phi);
|
|
std::complex<float> y(m_yRe, m_yIm);
|
|
std::complex<float> x(re, im);
|
|
|
|
std::complex<float> prod = x * m_y;
|
|
|
|
// Discriminator: cross * sign(dot) / dt
|
|
float cross = m_prod.real()*prod.imag() - prod.real()*m_prod.imag();
|
|
float dot = m_prod.real()*prod.real() + m_prod.imag()*prod.imag();
|
|
float eF = cross * (dot < 0 ? -1 : 1); // frequency error
|
|
|
|
// LPF section
|
|
float efHat = m_iir->run(eF);
|
|
|
|
m_freq = efHat; // correct instantaneous frequency
|
|
m_phi += efHat; // advance phase with instantaneous frequency
|
|
m_prod = prod; // store previous product
|
|
}
|
|
|