1 files changed, 153 insertions, 0 deletions
diff --git a/gr-digital/lib/digital_costas_loop_cc.cc b/gr-digital/lib/digital_costas_loop_cc.cc
new file mode 100644
index 000000000..370dc7e5c
--- /dev/null
+++ b/gr-digital/lib/digital_costas_loop_cc.cc
@@ -0,0 +1,153 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2006,2010,2011 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.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <digital_costas_loop_cc.h>
+#include <gr_io_signature.h>
+#include <gr_expj.h>
+#include <gr_sincos.h>
+#include <gr_math.h>
+
+digital_costas_loop_cc_sptr
+digital_make_costas_loop_cc (float loop_bw, int order
+			     ) throw (std::invalid_argument)
+{
+  return gnuradio::get_initial_sptr(new digital_costas_loop_cc 
+				    (loop_bw, order));
+}
+
+digital_costas_loop_cc::digital_costas_loop_cc (float loop_bw, int order
+						) throw (std::invalid_argument)
+  : gr_sync_block ("costas_loop_cc",
+		   gr_make_io_signature (1, 1, sizeof (gr_complex)),
+		   gr_make_io_signature2 (1, 2, sizeof (gr_complex), sizeof(float))),
+    gri_control_loop(loop_bw, 1.0, -1.0),
+    d_order(order), d_phase_detector(NULL)
+{
+  // Set up the phase detector to use based on the constellation order
+  switch(d_order) {
+  case 2:
+    d_phase_detector = &digital_costas_loop_cc::phase_detector_2;
+    break;
+
+  case 4:
+    d_phase_detector = &digital_costas_loop_cc::phase_detector_4;
+    break;
+
+  case 8:
+    d_phase_detector = &digital_costas_loop_cc::phase_detector_8;
+    break;
+
+  default: 
+    throw std::invalid_argument("order must be 2, 4, or 8");
+    break;
+  }
+}
+
+float
+digital_costas_loop_cc::phase_detector_8(gr_complex sample) const
+{
+  /* This technique splits the 8PSK constellation into 2 squashed
+     QPSK constellations, one when I is larger than Q and one where
+     Q is larger than I. The error is then calculated proportionally
+     to these squashed constellations by the const K = sqrt(2)-1.
+
+     The signal magnitude must be > 1 or K will incorrectly bias
+     the error value. 
+
+     Ref: Z. Huang, Z. Yi, M. Zhang, K. Wang, "8PSK demodulation for
+     new generation DVB-S2", IEEE Proc. Int. Conf. Communications,
+     Circuits and Systems, Vol. 2, pp. 1447 - 1450, 2004.
+  */
+
+  float K = (sqrt(2.0) - 1);
+  if(fabsf(sample.real()) >= fabsf(sample.imag())) {
+    return ((sample.real()>0 ? 1.0 : -1.0) * sample.imag() -
+	    (sample.imag()>0 ? 1.0 : -1.0) * sample.real() * K);
+  }
+  else {
+    return ((sample.real()>0 ? 1.0 : -1.0) * sample.imag() * K -
+	    (sample.imag()>0 ? 1.0 : -1.0) * sample.real());
+  }
+}
+
+float
+digital_costas_loop_cc::phase_detector_4(gr_complex sample) const
+{
+
+  return ((sample.real()>0 ? 1.0 : -1.0) * sample.imag() -
+	  (sample.imag()>0 ? 1.0 : -1.0) * sample.real());
+}
+
+float
+digital_costas_loop_cc::phase_detector_2(gr_complex sample) const
+{
+  return (sample.real()*sample.imag());
+}
+
+int
+digital_costas_loop_cc::work (int noutput_items,
+			      gr_vector_const_void_star &input_items,
+			      gr_vector_void_star &output_items)
+{
+  const gr_complex *iptr = (gr_complex *) input_items[0];
+  gr_complex *optr = (gr_complex *) output_items[0];
+  float *foptr = (float *) output_items[1];
+
+  bool write_foptr = output_items.size() >= 2;
+
+  float error;
+  gr_complex nco_out;
+  
+  if (write_foptr) {
+
+    for (int i = 0; i < noutput_items; i++){
+      nco_out = gr_expj(-d_phase);
+      optr[i] = iptr[i] * nco_out;
+      
+      error = (*this.*d_phase_detector)(optr[i]);
+      error = gr_branchless_clip(error, 1.0);
+	
+      advance_loop(error);
+      phase_wrap();
+      frequency_limit();
+      
+      foptr[i] = d_freq;
+    } 
+  } else {
+    for (int i = 0; i < noutput_items; i++){
+      nco_out = gr_expj(-d_phase);
+      optr[i] = iptr[i] * nco_out;
+      
+      error = (*this.*d_phase_detector)(optr[i]);
+      error = gr_branchless_clip(error, 1.0);
+
+      advance_loop(error);
+      phase_wrap();
+      frequency_limit();
+    }
+  }
+  return noutput_items;
+}