GNU Radio C++ API
digital_costas_loop_cc.h
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1 /* -*- c++ -*- */
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3  * Copyright 2006,2011 Free Software Foundation, Inc.
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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 
32 
33 /*!
34  * \brief A Costas loop carrier recovery module.
35  * \ingroup sync_blk
36  * \ingroup digital
37  *
38  * The Costas loop locks to the center frequency of a signal and
39  * downconverts it to baseband. The second (order=2) order loop is
40  * used for BPSK where the real part of the output signal is the
41  * baseband BPSK signal and the imaginary part is the error
42  * signal. When order=4, it can be used for quadrature modulations
43  * where both I and Q (real and imaginary) are outputted.
44  *
45  * More details can be found online:
46  *
47  * J. Feigin, "Practical Costas loop design: Designing a simple and
48  * inexpensive BPSK Costas loop carrier recovery circuit," RF signal
49  * processing, pp. 20-36, 2002.
50  *
51  * http://rfdesign.com/images/archive/0102Feigin20.pdf
52  *
53  * \param alpha the loop gain used for phase adjustment
54  * \param beta the loop gain for frequency adjustments
55  * \param max_freq the maximum frequency deviation (radians/sample) the loop can handle
56  * \param min_freq the minimum frequency deviation (radians/sample) the loop can handle
57  * \param order the loop order, either 2 or 4
58  */
59 
60 #include <digital_api.h>
61 
64 
65 
67 digital_make_costas_loop_cc (float loop_bw, int order
68  ) throw (std::invalid_argument);
69 
70 
71 /*!
72  * \brief Carrier tracking PLL for QPSK
73  * \ingroup sync_blk
74  * input: complex; output: complex
75  * <br>The Costas loop can have two output streams:
76  * stream 1 is the baseband I and Q;
77  * stream 2 is the normalized frequency of the loop
78  *
79  * \p order must be 2 or 4.
80  */
82 {
84  digital_make_costas_loop_cc (float loop_bw, int order
85  ) throw (std::invalid_argument);
86 
87  int d_order;
88 
89  digital_costas_loop_cc (float loop_bw, int order
90  ) throw (std::invalid_argument);
91 
92  /*! \brief the phase detector circuit for 8th-order PSK loops
93  * \param sample complex sample
94  * \return the phase error
95  */
96  float phase_detector_8(gr_complex sample) const; // for 8PSK
97 
98  /*! \brief the phase detector circuit for fourth-order loops
99  * \param sample complex sample
100  * \return the phase error
101  */
102  float phase_detector_4(gr_complex sample) const; // for QPSK
103 
104  /*! \brief the phase detector circuit for second-order loops
105  * \param sample a complex sample
106  * \return the phase error
107  */
108  float phase_detector_2(gr_complex sample) const; // for BPSK
109 
110 
111  float (digital_costas_loop_cc::*d_phase_detector)(gr_complex sample) const;
112 
113 public:
114 
115  int work (int noutput_items,
116  gr_vector_const_void_star &input_items,
117  gr_vector_void_star &output_items);
118 };
119 
120 #endif