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24 #ifndef INCLUDED_GR_COSTAS_LOOP_CC_H
25 #define INCLUDED_GR_COSTAS_LOOP_CC_H
27 #include <gr_sync_block.h>
32 /*! \brief A Costas loop carrier recovery module.
35 * The Costas loop locks to the center frequency of a signal and
36 * downconverts it to baseband. The second (order=2) order loop is
37 * used for BPSK where the real part of the output signal is the
38 * baseband BPSK signal and the imaginary part is the error
39 * signal. When order=4, it can be used for quadrature modulations
40 * where both I and Q (real and imaginary) are outputted.
42 * More details can be found online:
44 * J. Feigin, "Practical Costas loop design: Designing a simple and inexpensive
45 * BPSK Costas loop carrier recovery circuit," RF signal processing, pp. 20-36,
48 * http://rfdesign.com/images/archive/0102Feigin20.pdf
50 * \param alpha the loop gain used for phase adjustment
51 * \param beta the loop gain for frequency adjustments
52 * \param max_freq the maximum frequency deviation (radians/sample) the loop can handle
53 * \param min_freq the minimum frequency deviation (radians/sample) the loop can handle
54 * \param order the loop order, either 2 or 4
56 class gr_costas_loop_cc;
57 typedef boost::shared_ptr<gr_costas_loop_cc> gr_costas_loop_cc_sptr;
60 gr_costas_loop_cc_sptr
61 gr_make_costas_loop_cc (float alpha, float beta,
62 float max_freq, float min_freq,
64 ) throw (std::invalid_argument);
68 * \brief Carrier tracking PLL for QPSK
70 * input: complex; output: complex
71 * <br>The Costas loop can have two output streams:
72 * stream 1 is the baseband I and Q;
73 * stream 2 is the normalized frequency of the loop
75 * \p order must be 2 or 4.
77 class gr_costas_loop_cc : public gr_sync_block
79 friend gr_costas_loop_cc_sptr gr_make_costas_loop_cc (float alpha, float beta,
80 float max_freq, float min_freq,
82 ) throw (std::invalid_argument);
84 float d_alpha, d_beta, d_max_freq, d_min_freq, d_phase, d_freq;
87 gr_costas_loop_cc (float alpha, float beta,
88 float max_freq, float min_freq,
90 ) throw (std::invalid_argument);
92 /*! \brief the phase detector circuit for fourth-order loops
93 * \param sample complex sample
94 * \return the phase error
96 float phase_detector_4(gr_complex sample) const; // for QPSK
98 /*! \brief the phase detector circuit for second-order loops
99 * \param sample a complex sample
100 * \return the phase error
102 float phase_detector_2(gr_complex sample) const; // for BPSK
105 float (gr_costas_loop_cc::*d_phase_detector)(gr_complex sample) const;
109 /*! \brief set the first order gain
112 void set_alpha(float alpha);
114 /*! \brief get the first order gain
117 float alpha() const { return d_alpha; }
119 /*! \brief set the second order gain
122 void set_beta(float beta);
124 /*! \brief get the second order gain
127 float beta() const { return d_beta; }
129 int work (int noutput_items,
130 gr_vector_const_void_star &input_items,
131 gr_vector_void_star &output_items);
133 /*! \brief returns the current NCO frequency in radians/sample
136 float freq() const { return d_freq; }