mirror of
https://github.com/f4exb/sdrangel.git
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68 lines
2.7 KiB
C
68 lines
2.7 KiB
C
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///////////////////////////////////////////////////////////////////////////////////
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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 "dsp/dsptypes.h"
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/** Phase-locked loop mainly for broadcadt FM stereo pilot. */
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class 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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/**
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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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/**
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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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*/
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void process(const std::vector<Real>& samples_in, std::vector<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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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, m_phase;
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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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};
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