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New PLL: implemented trick on the phase comparator for M-ary PSK operation
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@ -3,7 +3,9 @@
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// written by Edouard Griffiths //
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// written by Edouard Griffiths //
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// //
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// //
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// See: http://liquidsdr.org/blog/pll-howto/ //
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// See: http://liquidsdr.org/blog/pll-howto/ //
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// Fixes filter registers saturation //
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// Fixed filter registers saturation //
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// Added order for PSK locking. This brilliant idea actually comes from this //
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// post: https://www.dsprelated.com/showthread/comp.dsp/36356-1.php //
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// //
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// //
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// This program is free software; you can redistribute it and/or modify //
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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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// it under the terms of the GNU General Public License as published by //
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@ -37,7 +39,8 @@ PhaseLockComplex::PhaseLockComplex() :
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m_y(1.0, 0.0),
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m_y(1.0, 0.0),
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m_yRe(1.0),
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m_yRe(1.0),
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m_yIm(0.0),
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m_yIm(0.0),
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m_freq(0.0)
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m_freq(0.0),
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m_pskOrder(1)
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{
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{
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}
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}
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@ -71,6 +74,11 @@ void PhaseLockComplex::computeCoefficients(Real wn, Real zeta, Real K)
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reset();
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reset();
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}
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}
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void PhaseLockComplex::setPskOrder(unsigned int order)
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{
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m_pskOrder = order > 0 ? order : 1;
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}
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void PhaseLockComplex::reset()
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void PhaseLockComplex::reset()
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{
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{
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// reset filter accumulators and phase
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// reset filter accumulators and phase
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@ -96,6 +104,11 @@ void PhaseLockComplex::feed(float re, float im)
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std::complex<float> x(re, im);
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std::complex<float> x(re, im);
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m_deltaPhi = std::arg(x * std::conj(m_y));
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m_deltaPhi = std::arg(x * std::conj(m_y));
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// bring phase 0 on any of the PSK symbols
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if (m_pskOrder > 1) {
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m_deltaPhi = normalizeAngle(m_pskOrder*m_deltaPhi);
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}
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// advance buffer
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// advance buffer
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m_v2 = m_v1; // shift center register to upper register
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m_v2 = m_v1; // shift center register to upper register
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m_v1 = m_v0; // shift lower register to center register
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m_v1 = m_v0; // shift lower register to center register
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@ -134,4 +147,13 @@ void PhaseLockComplex::feed(float re, float im)
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m_phiHatLast = m_phiHat;
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m_phiHatLast = m_phiHat;
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}
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}
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float PhaseLockComplex::normalizeAngle(float angle)
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{
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while (angle <= -M_PI) {
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angle += 2.0*M_PI;
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}
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while (angle > M_PI) {
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angle -= 2.0*M_PI;
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}
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return angle;
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}
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@ -3,7 +3,9 @@
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// written by Edouard Griffiths //
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// written by Edouard Griffiths //
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// //
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// //
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// See: http://liquidsdr.org/blog/pll-howto/ //
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// See: http://liquidsdr.org/blog/pll-howto/ //
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// Fixes filter registers saturation //
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// Fixed filter registers saturation //
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// Added order for PSK locking. This brilliant idea actually comes from this //
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// post: https://www.dsprelated.com/showthread/comp.dsp/36356-1.php //
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// //
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// //
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// This program is free software; you can redistribute it and/or modify //
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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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// it under the terms of the GNU General Public License as published by //
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@ -35,6 +37,10 @@ public:
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* \param K PLL loop gain
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* \param K PLL loop gain
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* */
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* */
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void computeCoefficients(Real wn, Real zeta, Real K);
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void computeCoefficients(Real wn, Real zeta, Real K);
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/** Set the PSK order for the phase comparator
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* \param order 0,1: no PSK (CW), 2: BPSK, 4: QPSK, 8: 8-PSK, ... use powers of two for real cases
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*/
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void setPskOrder(unsigned int order);
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void reset();
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void reset();
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void feed(float re, float im);
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void feed(float re, float im);
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const std::complex<float>& getComplex() const { return m_y; }
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const std::complex<float>& getComplex() const { return m_y; }
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@ -46,6 +52,9 @@ public:
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float getPhiHat() const { return m_phiHat; }
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float getPhiHat() const { return m_phiHat; }
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private:
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private:
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/** Normalize angle in radians into the [-pi,+pi] region */
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static float normalizeAngle(float angle);
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// a0 = 1 is implied
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// a0 = 1 is implied
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float m_a1;
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float m_a1;
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float m_a2;
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float m_a2;
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@ -62,7 +71,7 @@ private:
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float m_yRe;
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float m_yRe;
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float m_yIm;
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float m_yIm;
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float m_freq;
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float m_freq;
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unsigned int m_pskOrder;
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};
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};
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