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100 lines
4.2 KiB
C++
100 lines
4.2 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2012 maintech GmbH, Otto-Hahn-Str. 15, 97204 Hoechberg, Germany //
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// written by Christian Daniel //
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// Copyright (C) 2015-2019 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
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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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// (at your option) any later version. //
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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_NCO_H
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#define INCLUDE_NCO_H
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#include "dsp/dsptypes.h"
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#include "export.h"
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// Numerically Controlled Oscillator (NCO), using 2^12 entry 32-bit LUT and Q12.20 fixed-point phase accumulator with linear interpolation
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// With a 2^12 32-bit LUT, SFDR is 144 dBc. 2^13 would be 156 dBc.
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// Fractional part can be set to 0 by setting integerPhase = true, to increase SFDR while decreasing frequency accuracy.
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// Frequency accuracy = sampleRate / 2^PhaseBits.
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// So:
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// 48k / 2^32 = 0.00001 Hz
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// 48k / 2^12 = 15.2 Hz (integer only)
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// 2M / 2^32 = 0.00046 Hz
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// 2M / 2^12 = 488 Hz (integer only)
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class SDRBASE_API NCO {
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private:
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#ifdef NCO_64_BIT
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constexpr static unsigned PhaseBits = 64;
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typedef uint64_t Phase;
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typedef double Frac;
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#else
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constexpr static unsigned PhaseBits = 32;
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typedef uint32_t Phase;
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typedef float Frac;
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#endif
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constexpr static unsigned TableBits = 12;
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constexpr static unsigned TableSize = 1 << TableBits;
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constexpr static unsigned IntShift = PhaseBits - TableBits;
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constexpr static Phase IntMask = TableSize - 1u;
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constexpr static Phase FracMask = ((1ull << IntShift) - 1u);
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constexpr static Frac Denom = 1ull << IntShift;
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static Real m_table[TableSize];
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static bool m_tableInitialized;
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static void initTable();
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uint64_t prsg63();
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Phase m_phaseIncrement;
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Phase m_phase;
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Phase m_phaseDithered;
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uint64_t m_lfsr; // Linear feedback shift register for psuedo random number generation
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Phase m_ditherMask; // Bit mask to select bits from lfsr to use for phase dithering
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public:
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NCO();
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void setFreq(Real freq, Real sampleRate, bool integerPhase = false, int ditherBits = 0);
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void setPhase(Phase phase) { m_phase = phase; }
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void nextPhase() //!< Increment phase
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{
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m_phase += m_phaseIncrement; // No need to wrap, as that is handled by overflow
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m_phaseDithered = m_phase;
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if (m_ditherMask) {
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m_phaseDithered += prsg63() & m_ditherMask;
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}
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}
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Real next(); //!< Return next real sample
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Complex nextIQ(); //!< Return next complex sample
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Complex nextQI(); //!< Return next complex sample (reversed)
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Complex nextIQ(float imbalance); //!< Return next complex sample with an imbalance factor on I
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void nextIQMul(Real& i, Real& q); //!< multiply I,Q separately with next sample
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Real get() const; //!< Return current real sample (no phase increment)
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Complex getIQ() const; //!< Return current complex sample (no phase increment)
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void getIQ(Complex& c) const; //!< Sets to the current complex sample (no phase increment)
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Complex getQI() const; //!< Return current complex sample (no phase increment, reversed)
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void getQI(Complex& c) const; //!< Sets to the current complex sample (no phase increment, reversed)
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};
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#endif // INCLUDE_NCO_H
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