mirror of
https://github.com/f4exb/sdrangel.git
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179 lines
5.8 KiB
C++
179 lines
5.8 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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#include <vector>
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#include "dsp/dsptypes.h"
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#include "export.h"
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/** Phase-locked loop mainly for broadcadt FM stereo pilot. */
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class SDRBASE_API PhaseLock
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{
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public:
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/** Expected pilot frequency (used for PPS events). */
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static const int pilot_frequency = 19000;
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/** Timestamp event produced once every 19000 pilot periods. */
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struct PpsEvent
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{
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quint64 pps_index;
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quint64 sample_index;
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double block_position;
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};
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/**
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* Construct phase-locked loop.
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*
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* freq :: 19 kHz center frequency relative to sample freq
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* (0.5 is Nyquist)
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* bandwidth :: bandwidth relative to sample frequency
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* minsignal :: minimum pilot amplitude
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*/
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PhaseLock(Real freq, Real bandwidth, Real minsignal);
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virtual ~PhaseLock()
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{}
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/**
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* Change phase locked loop parameters
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*
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* freq :: 19 kHz center frequency relative to sample freq
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* (0.5 is Nyquist)
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* bandwidth :: bandwidth relative to sample frequency
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* minsignal :: minimum pilot amplitude
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*/
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void configure(Real freq, Real bandwidth, Real minsignal);
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/**
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* Process samples and extract 19 kHz pilot tone.
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* Generate phase-locked 38 kHz tone with unit amplitude.
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* Bufferized version with input and output vectors
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*/
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void process(const std::vector<Real>& samples_in, std::vector<Real>& samples_out);
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/**
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* Process samples and track a pilot tone. Generate samples for single or multiple phase-locked
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* signals. Implement the processPhase virtual method to produce the output samples.
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* In flow version. Ex: Use 19 kHz stereo pilot tone to generate 38 kHz (stereo) and 57 kHz
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* pilots (see RDSPhaseLock class below).
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* This is the in flow version
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*/
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void process(const Real& sample_in, Real *samples_out);
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/** Return true if the phase-locked loop is locked. */
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bool locked() const
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{
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return m_lock_cnt >= m_lock_delay;
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}
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/** Return detected amplitude of pilot signal. */
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Real get_pilot_level() const
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{
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return 2 * m_pilot_level;
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}
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protected:
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Real m_phase;
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Real m_psin;
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Real m_pcos;
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/**
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* Callback method to produce multiple outputs from the current phase value in m_phase
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* and/or the sin and cos values in m_psin and m_pcos
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*/
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virtual void processPhase(Real *samples_out __attribute__((unused))) const {};
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private:
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Real m_minfreq, m_maxfreq;
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Real m_phasor_b0, m_phasor_a1, m_phasor_a2;
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Real m_phasor_i1, m_phasor_i2, m_phasor_q1, m_phasor_q2;
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Real m_loopfilter_b0, m_loopfilter_b1;
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Real m_loopfilter_x1;
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Real m_freq;
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Real m_minsignal;
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Real m_pilot_level;
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int m_lock_delay;
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int m_lock_cnt;
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int m_pilot_periods;
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quint64 m_pps_cnt;
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quint64 m_sample_cnt;
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std::vector<PpsEvent> m_pps_events;
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};
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class SimplePhaseLock : public PhaseLock
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{
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public:
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SimplePhaseLock(Real freq, Real bandwidth, Real minsignal) :
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PhaseLock(freq, bandwidth, minsignal)
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{}
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virtual ~SimplePhaseLock()
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{}
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protected:
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virtual void processPhase(Real *samples_out) const
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{
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samples_out[0] = m_psin; // f Pilot
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samples_out[1] = m_pcos; // f Pilot
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}
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};
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class StereoPhaseLock : public PhaseLock
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{
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public:
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StereoPhaseLock(Real freq, Real bandwidth, Real minsignal) :
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PhaseLock(freq, bandwidth, minsignal)
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{}
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virtual ~StereoPhaseLock()
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{}
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protected:
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virtual void processPhase(Real *samples_out) const
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{
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samples_out[0] = m_psin; // f Pilot
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// Generate double-frequency output.
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// sin(2*x) = 2 * sin(x) * cos(x)
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samples_out[1] = 2.0 * m_psin * m_pcos; // 2f Pilot sin
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// cos(2*x) = 2 * cos(x) * cos(x) - 1
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samples_out[2] = (2.0 * m_pcos * m_pcos) - 1.0; // 2f Pilot cos
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}
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};
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class RDSPhaseLock : public PhaseLock
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{
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public:
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RDSPhaseLock(Real freq, Real bandwidth, Real minsignal) :
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PhaseLock(freq, bandwidth, minsignal)
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{}
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virtual ~RDSPhaseLock()
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{}
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protected:
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virtual void processPhase(Real *samples_out) const
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{
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samples_out[0] = m_psin; // Pilot signal (f)
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// Generate double-frequency output.
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// sin(2*x) = 2 * sin(x) * cos(x)
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samples_out[1] = 2.0 * m_psin * m_pcos; // Pilot signal (2f)
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// cos(2*x) = 2 * cos(x) * cos(x) - 1
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samples_out[2] = (2.0 * m_pcos * m_pcos) - 1.0; // 2f Pilot cos
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samples_out[3] = m_phase; // Pilot phase
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}
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};
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