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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>
31 class gr_costas_loop_cc;
32 typedef boost::shared_ptr<gr_costas_loop_cc> gr_costas_loop_cc_sptr;
34 /*! \brief A Costas loop carrier recovery module.
36 * The Costas loop locks to the center frequency of a signal and
37 * downconverts it to baseband. The second (order=2) order loop is
38 * used for BPSK where the real part of the output signal is the
39 * baseband BPSK signal and the imaginary part is the error
40 * signal. When order=4, it can be used for quadrature modulations
41 * where both I and Q (real and imaginary) are outputted.
43 * More details can be found online:
45 * J. Feigin, "Practical Costas loop design: Designing a simple and inexpensive
46 * BPSK Costas loop carrier recovery circuit," RF signal processing, pp. 20-36,
49 * http://rfdesign.com/images/archive/0102Feigin20.pdf
51 * \param alpha the loop gain used for phase adjustment
52 * \param beta the loop gain for frequency adjustments
53 * \param max_freq the maximum frequency deviation (normalized frequency) the loop can handle
54 * \param min_freq the minimum frequency deviation (normalized frequency) the loop can handle
55 * \param order the loop order, either 2 or 4
57 gr_costas_loop_cc_sptr
58 gr_make_costas_loop_cc (float alpha, float beta,
59 float max_freq, float min_freq,
61 ) throw (std::invalid_argument);
65 * \brief Carrier tracking PLL for QPSK
67 * input: complex; output: complex
68 * <br>The Costas loop can have two output streams:
69 * stream 1 is the baseband I and Q;
70 * stream 2 is the normalized frequency of the loop
72 * \p order must be 2 or 4.
74 class gr_costas_loop_cc : public gr_sync_block
76 friend gr_costas_loop_cc_sptr gr_make_costas_loop_cc (float alpha, float beta,
77 float max_freq, float min_freq,
79 ) throw (std::invalid_argument);
81 float d_alpha, d_beta, d_max_freq, d_min_freq, d_phase, d_freq;
84 gr_costas_loop_cc (float alpha, float beta,
85 float max_freq, float min_freq,
87 ) throw (std::invalid_argument);
89 /*! \brief the phase detector circuit for fourth-order loops
90 * \param sample complex sample
91 * \return the phase error
93 float phase_detector_4(gr_complex sample) const; // for QPSK
95 /*! \breif the phase detector circuit for second-order loops
96 * \param a complex sample
97 * \return the phase error
99 float phase_detector_2(gr_complex sample) const; // for BPSK
102 float (gr_costas_loop_cc::*d_phase_detector)(gr_complex sample) const;
106 int work (int noutput_items,
107 gr_vector_const_void_star &input_items,
108 gr_vector_void_star &output_items);