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201 lines
5.9 KiB
C++
201 lines
5.9 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2015 F4EXB //
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// written by Edouard Griffiths //
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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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#ifndef INCLUDE_DSP_PHASEDISCRI_H_
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#define INCLUDE_DSP_PHASEDISCRI_H_
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#include "dsp/dsptypes.h"
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#undef M_PI
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#define M_PI 3.14159265358979323846
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class PhaseDiscriminators
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{
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public:
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/**
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* Reset stored values
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*/
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void reset()
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{
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m_m1Sample = 0;
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m_m2Sample = 0;
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}
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/**
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* Scaling factor so that resulting excursion maps to [-1,+1]
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*/
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void setFMScaling(Real fmScaling)
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{
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m_fmScaling = fmScaling;
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}
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/**
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* Standard discriminator using atan2. On modern processors this is as efficient as the non atan2 one.
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* This is better for high fidelity.
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*/
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Real phaseDiscriminator(const Complex& sample)
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{
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Complex d(std::conj(m_m1Sample) * sample);
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m_m1Sample = sample;
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return (std::atan2(d.imag(), d.real()) / M_PI) * m_fmScaling;
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}
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/**
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* Discriminator with phase detection using atan2 and frequency by derivation.
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* This yields a precise deviation to sample rate ratio: Sample rate => +/-1.0
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*/
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Real phaseDiscriminatorDelta(const Complex& sample, double& magsq, Real& fmDev)
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{
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Real fltI = sample.real();
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Real fltQ = sample.imag();
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magsq = fltI*fltI + fltQ*fltQ;
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Real curArg = atan2_approximation2((float) fltQ, (float) fltI);
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fmDev = (curArg - m_prevArg) / M_PI;
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m_prevArg = curArg;
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if (fmDev < -1.0f) {
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fmDev += 2.0f;
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} else if (fmDev > 1.0f) {
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fmDev -= 2.0f;
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}
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return fmDev * m_fmScaling;
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}
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/**
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* Alternative without atan at the expense of a slight distorsion on very wideband signals
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* http://www.embedded.com/design/configurable-systems/4212086/DSP-Tricks--Frequency-demodulation-algorithms-
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* in addition it needs scaling by instantaneous magnitude squared and volume (0..10) adjustment factor
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*/
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Real phaseDiscriminator2(const Complex& sample)
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{
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Real ip = sample.real() - m_m2Sample.real();
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Real qp = sample.imag() - m_m2Sample.imag();
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Real h1 = m_m1Sample.real() * qp;
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Real h2 = m_m1Sample.imag() * ip;
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m_m2Sample = m_m1Sample;
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m_m1Sample = sample;
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//return ((h1 - h2) / M_PI_2) * m_fmScaling;
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return (h1 - h2) * m_fmScaling;
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}
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/**
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* Second alternative
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*/
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Real phaseDiscriminator3(const Complex& sample, long double& magsq, Real& fltVal)
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{
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Real fltI = sample.real();
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Real fltQ = sample.imag();
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double fltNorm;
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Real fltNormI;
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Real fltNormQ;
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//Real fltVal;
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magsq = fltI*fltI + fltQ*fltQ;
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fltNorm = std::sqrt(magsq);
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fltNormI= fltI/fltNorm;
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fltNormQ= fltQ/fltNorm;
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fltVal = m_fltPreviousI*(fltNormQ - m_fltPreviousQ2);
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fltVal -= m_fltPreviousQ*(fltNormI - m_fltPreviousI2);
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fltVal += 2.0f;
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fltVal /= 4.0f; // normally it is /4
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m_fltPreviousQ2 = m_fltPreviousQ;
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m_fltPreviousI2 = m_fltPreviousI;
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m_fltPreviousQ = fltNormQ;
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m_fltPreviousI = fltNormI;
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return fltVal * m_fmScaling;
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}
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private:
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Complex m_m1Sample;
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Complex m_m2Sample;
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Real m_fmScaling;
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Real m_fltPreviousI;
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Real m_fltPreviousQ;
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Real m_fltPreviousI2;
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Real m_fltPreviousQ2;
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Real m_prevArg;
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float atan2_approximation1(float y, float x)
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{
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//http://pubs.opengroup.org/onlinepubs/009695399/functions/atan2.html
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//Volkan SALMA
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const float ONEQTR_PI = M_PI / 4.0;
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const float THRQTR_PI = 3.0 * M_PI / 4.0;
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float r, angle;
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float abs_y = std::fabs(y) + 1e-10f; // kludge to prevent 0/0 condition
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if ( x < 0.0f )
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{
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r = (x + abs_y) / (abs_y - x);
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angle = THRQTR_PI;
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}
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else
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{
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r = (x - abs_y) / (x + abs_y);
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angle = ONEQTR_PI;
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}
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angle += (0.1963f * r * r - 0.9817f) * r;
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if ( y < 0.0f )
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return( -angle ); // negate if in quad III or IV
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else
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return( angle );
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}
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#define PI_FLOAT 3.14159265f
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#define PIBY2_FLOAT 1.5707963f
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// |error| < 0.005
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float atan2_approximation2( float y, float x )
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{
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if ( x == 0.0f )
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{
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if ( y > 0.0f ) return PIBY2_FLOAT;
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if ( y == 0.0f ) return 0.0f;
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return -PIBY2_FLOAT;
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}
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float atan;
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float z = y/x;
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if ( std::fabs( z ) < 1.0f )
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{
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atan = z/(1.0f + 0.28f*z*z);
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if ( x < 0.0f )
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{
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if ( y < 0.0f ) return atan - PI_FLOAT;
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return atan + PI_FLOAT;
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}
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}
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else
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{
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atan = PIBY2_FLOAT - z/(z*z + 0.28f);
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if ( y < 0.0f ) return atan - PI_FLOAT;
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}
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return atan;
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}
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};
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#endif /* INCLUDE_DSP_PHASEDISCRI_H_ */
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