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Added a frequency lock loop

This commit is contained in:
f4exb 2018-05-17 01:05:48 +02:00
parent c495f82235
commit d29958d51f
3 changed files with 188 additions and 0 deletions
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4
sdrbase/CMakeLists.txt
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@ -34,6 +34,7 @@ set(sdrbase_SOURCES
dsp/filterrc.cpp
dsp/filtermbe.cpp
dsp/filerecord.cpp
dsp/freqlockcomplex.cpp
dsp/interpolator.cpp
dsp/hbfiltertraits.cpp
dsp/lowpass.cpp
@ -124,6 +125,7 @@ set(sdrbase_HEADERS
dsp/filterrc.h
dsp/filtermbe.h
dsp/filerecord.h
dsp/freqlockcomplex.h
dsp/gfft.h
dsp/iirfilter.h
dsp/interpolator.h
@ -271,6 +273,7 @@ include_directories(
.
${CMAKE_SOURCE_DIR}/exports
${CMAKE_SOURCE_DIR}/httpserver
${CMAKE_SOURCE_DIR}/kitiirfir
${CMAKE_SOURCE_DIR}/qrtplib
${CMAKE_SOURCE_DIR}/swagger/sdrangel/code/qt5/client
)
@ -278,6 +281,7 @@ include_directories(
target_link_libraries(sdrbase
${QT_LIBRARIES}
httpserver
kitiirfir
qrtplib
swagger
)

122
sdrbase/dsp/freqlockcomplex.cpp Normal file
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@ -0,0 +1,122 @@
///////////////////////////////////////////////////////////////////////////////////
// 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
}

62
sdrbase/dsp/freqlockcomplex.h Normal file
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@ -0,0 +1,62 @@
///////////////////////////////////////////////////////////////////////////////////
// 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/>. //
///////////////////////////////////////////////////////////////////////////////////
#ifndef SDRBASE_DSP_FREQLOCKCOMPLEX_H_
#define SDRBASE_DSP_FREQLOCKCOMPLEX_H_
#include "dsp/dsptypes.h"
#include "iirfilter.h"
#include "export.h"
/** General purpose Phase-locked loop using complex analytic signal input. */
class SDRBASE_API FreqLockComplex
{
public:
FreqLockComplex();
~FreqLockComplex();
void reset();
void computeCoefficients(float wn);
/** Feed PLL with a new signa sample */
void feed(float re, float im);
private:
float m_a0;
float m_a1;
float m_a2;
float m_b0;
float m_b1;
float m_b2;
float m_v0;
float m_v1;
float m_v2;
std::complex<float> m_y;
std::complex<float> m_prod;
float m_yRe;
float m_yIm;
float m_freq;
float m_phi;
IIRFilter<float, 2> *m_iir;
};
#endif /* SDRBASE_DSP_FREQLOCKCOMPLEX_H_ */