GNU Radio 3.6.2 C++ API
digital_cma_equalizer_cc.h
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1 /* -*- c++ -*- */
2 /*
3  * Copyright 2011 Free Software Foundation, Inc.
4  *
5  * This file is part of GNU Radio
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22 
23 #ifndef INCLUDED_DIGITAL_CMA_EQUALIZER_CC_H
24 #define INCLUDED_DIGITAL_CMA_EQUALIZER_CC_H
25 
26 #include <digital_api.h>
27 #include <gr_adaptive_fir_ccc.h>
28 #include <gr_math.h>
29 #include <iostream>
30 
33 
35 digital_make_cma_equalizer_cc(int num_taps, float modulus, float mu, int sps);
36 
37 /*!
38  * \brief Implements constant modulus adaptive filter on complex stream
39  * \ingroup eq_blk
40  * \ingroup digital
41  *
42  * The error value and tap update equations (for p=2) can be found in:
43  *
44  * "D. Godard, "Self-Recovering Equalization and Carrier Tracking in
45  * Two-Dimensional Data Communication Systems," IEEE Transactions on
46  * Communications, Vol. 28, No. 11, pp. 1867 - 1875, 1980."
47  */
49 {
50 private:
51  float d_modulus;
52  float d_mu;
53 
55  float modulus,
56  float mu,
57  int sps);
58  digital_cma_equalizer_cc(int num_taps, float modulus, float mu, int sps);
59 
60 protected:
61 
62  virtual gr_complex error(const gr_complex &out)
63  {
64  gr_complex error = out*(norm(out) - d_modulus);
65  float re = gr_clip(error.real(), 1.0);
66  float im = gr_clip(error.imag(), 1.0);
67  return gr_complex(re, im);
68  }
69 
70  virtual void update_tap(gr_complex &tap, const gr_complex &in)
71  {
72  // Hn+1 = Hn - mu*conj(Xn)*zn*(|zn|^2 - 1)
73  tap -= d_mu*conj(in)*d_error;
74  }
75 
76 public:
77  float get_gain()
78  {
79  return d_mu;
80  }
81 
82  void set_gain(float mu)
83  {
84  if(mu < 0.0f || mu > 1.0f) {
85  throw std::out_of_range("digital_cma_equalizer::set_gain: Gain value must be in [0,1]");
86  }
87  d_mu = mu;
88  }
89 
90  float get_modulus()
91  {
92  return d_modulus;
93  }
94 
95  void set_modulus(float mod)
96  {
97  if(mod < 0)
98  throw std::out_of_range("digital_cma_equalizer::set_modulus: Modulus value must be >= 0");
99  d_modulus = mod;
100  }
101 };
102 
103 #endif