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79 lines
2.7 KiB
C++
79 lines
2.7 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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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_2) * 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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}
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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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};
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#endif /* INCLUDE_DSP_PHASEDISCRI_H_ */
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