1 files changed, 112 insertions, 0 deletions
diff --git a/gr-digital/include/digital_kurtotic_equalizer_cc.h b/gr-digital/include/digital_kurtotic_equalizer_cc.h
new file mode 100644
index 000000000..018a906b0
--- /dev/null
+++ b/gr-digital/include/digital_kurtotic_equalizer_cc.h
@@ -0,0 +1,112 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2011 Free Software Foundation, Inc.
+ * 
+ * This file is part of GNU Radio
+ * 
+ * GNU Radio is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3, or (at your option)
+ * any later version.
+ * 
+ * GNU Radio is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with GNU Radio; see the file COPYING.  If not, write to
+ * the Free Software Foundation, Inc., 51 Franklin Street,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifndef INCLUDED_DIGITAL_KURTOTIC_EQUALIZER_CC_H
+#define	INCLUDED_DIGITAL_KURTOTIC_EQUALIZER_CC_H
+
+#include <gr_adaptive_fir_ccc.h>
+#include <gr_math.h>
+#include <iostream>
+
+class digital_kurtotic_equalizer_cc;
+typedef boost::shared_ptr<digital_kurtotic_equalizer_cc> digital_kurtotic_equalizer_cc_sptr;
+
+digital_kurtotic_equalizer_cc_sptr 
+digital_make_kurtotic_equalizer_cc(int num_taps, float mu);
+
+/*!
+ * \brief Implements a kurtosis-based adaptive equalizer on complex stream
+ * \ingroup eq_blk
+ * \ingroup digital
+ *
+ * Y. Guo, J. Zhao, Y. Sun, "Sign kurtosis maximization based blind
+ * equalization algorithm," IEEE Conf. on Control, Automation,
+ * Robotics and Vision, Vol. 3, Dec. 2004, pp. 2052 - 2057.
+ */
+class digital_kurtotic_equalizer_cc : public gr_adaptive_fir_ccc
+{
+private:
+  float d_mu;
+  float d_p, d_m;
+  gr_complex d_q, d_u;
+  float d_alpha_p, d_alpha_q, d_alpha_m;
+  
+  friend digital_kurtotic_equalizer_cc_sptr digital_make_kurtotic_equalizer_cc(int num_taps,
+									       float mu);
+  digital_kurtotic_equalizer_cc(int num_taps, float mu);
+
+  gr_complex sign(gr_complex x)
+  {
+    float re = (float)(x.real() >= 0.0f);
+    float im = (float)(x.imag() >= 0.0f);
+    return gr_complex(re, im);
+  }
+
+protected:
+
+  virtual gr_complex error(const gr_complex &out) 
+  {
+
+    // p = E[|z|^2]
+    // q = E[z^2]
+    // m = E[|z|^4]
+    // u = E[kurtosis(z)]
+
+    float nrm = norm(out);
+    gr_complex cnj = conj(out);
+    float epsilon_f = 1e-12;
+    gr_complex epsilon_c = gr_complex(1e-12, 1e-12);
+
+    
+    d_p = (1-d_alpha_p)*d_p + (d_alpha_p)*nrm + epsilon_f;
+    d_q = (1-d_alpha_q)*d_q + (d_alpha_q)*out*out + epsilon_c;
+    d_m = (1-d_alpha_m)*d_m + (d_alpha_m)*nrm*nrm + epsilon_f;
+    d_u = d_m - 2.0f*(d_p*d_p) - d_q*d_q;
+
+    gr_complex F = (1.0f / (d_p*d_p*d_p)) *
+      (sign(d_u) * (nrm*cnj - 2.0f*d_p*cnj - conj(d_q)*out) -
+       abs(d_u)*cnj);
+
+    //std::cout << "out: " << out << "   p: " << d_p << "   q: " << d_q;
+    //std::cout << "   m: " << d_m << "   u: " << d_u << std::endl;
+    //std::cout << "error: " << F << std::endl;
+    
+    float re = gr_clip(F.real(), 1.0);
+    float im = gr_clip(F.imag(), 1.0);
+    return gr_complex(re, im);
+  }
+
+  virtual void update_tap(gr_complex &tap, const gr_complex &in) 
+  {
+    tap += d_mu*in*d_error;
+  }
+  
+public:
+  void set_gain(float mu) 
+  {
+    if(mu < 0)
+      throw std::out_of_range("digital_kurtotic_equalizer::set_gain: Gain value must be >= 0");
+    d_mu = mu;
+  }
+};
+
+#endif