GNU Radio 3.6.5.1 C++ API
digital_costas_loop_cc.h
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1 /* -*- c++ -*- */
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22 
23 
24 #ifndef INCLUDED_DIGITAL_COSTAS_LOOP_CC_H
25 #define INCLUDED_DIGITAL_COSTAS_LOOP_CC_H
26 
27 #include <gr_sync_block.h>
28 #include <gri_control_loop.h>
29 #include <stdexcept>
30 #include <fstream>
31 #include <digital_api.h>
32 
35 
36 
38 digital_make_costas_loop_cc (float loop_bw, int order
39  ) throw (std::invalid_argument);
40 
41 /*!
42  * \brief A Costas loop carrier recovery module.
43  * \ingroup synchronizers_blk
44  *
45  * \details
46  * The Costas loop locks to the center frequency of a signal and
47  * downconverts it to baseband. The second (order=2) order loop is
48  * used for BPSK where the real part of the output signal is the
49  * baseband BPSK signal and the imaginary part is the error
50  * signal. When order=4, it can be used for quadrature modulations
51  * where both I and Q (real and imaginary) are outputted.
52  *
53  * More details can be found online:
54  *
55  * J. Feigin, "Practical Costas loop design: Designing a simple and
56  * inexpensive BPSK Costas loop carrier recovery circuit," RF signal
57  * processing, pp. 20-36, 2002.
58  *
59  * http://rfdesign.com/images/archive/0102Feigin20.pdf
60  */
62 {
64  digital_make_costas_loop_cc (float loop_bw, int order
65  ) throw (std::invalid_argument);
66 
67  int d_order;
68 
69  /*!
70  * \brief Carrier tracking PLL for QPSK
71  * input: complex; output: complex
72  * <br>The Costas loop can have two output streams:
73  * stream 1 is the baseband I and Q;
74  * stream 2 is the normalized frequency of the loop
75  *
76  * \param loop_bw internal 2nd order loop bandwidth (~ 2pi/100)
77  * \param order the loop order, either 2, 4, or 8
78  */
79  digital_costas_loop_cc (float loop_bw, int order
80  ) throw (std::invalid_argument);
81 
82  /*! \brief the phase detector circuit for 8th-order PSK loops
83  * \param sample complex sample
84  * \return the phase error
85  */
86  float phase_detector_8(gr_complex sample) const; // for 8PSK
87 
88  /*! \brief the phase detector circuit for fourth-order loops
89  * \param sample complex sample
90  * \return the phase error
91  */
92  float phase_detector_4(gr_complex sample) const; // for QPSK
93 
94  /*! \brief the phase detector circuit for second-order loops
95  * \param sample a complex sample
96  * \return the phase error
97  */
98  float phase_detector_2(gr_complex sample) const; // for BPSK
99 
100 
101  float (digital_costas_loop_cc::*d_phase_detector)(gr_complex sample) const;
102 
103 public:
104 
105  int work (int noutput_items,
106  gr_vector_const_void_star &input_items,
107  gr_vector_void_star &output_items);
108 };
109 
110 #endif