X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=gr-atsc%2Fsrc%2Flib%2Fatsc_fpll.cc;fp=gr-atsc%2Fsrc%2Flib%2Fatsc_fpll.cc;h=f5bf39d20ff8459d6e68841aeacaeae56e2405e0;hb=35e43e8d8c271e6842191cac3fc3f2f88a861183;hp=0000000000000000000000000000000000000000;hpb=ea29b08aeb54227e6628f655ccfdb96fe4d8c378;p=debian%2Fgnuradio

diff --git a/gr-atsc/src/lib/atsc_fpll.cc b/gr-atsc/src/lib/atsc_fpll.cc
new file mode 100644
index 00000000..f5bf39d2
--- /dev/null
+++ b/gr-atsc/src/lib/atsc_fpll.cc
@@ -0,0 +1,137 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2006 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 <atsc_fpll.h>
+#include <gr_io_signature.h>
+#include <atsc_consts.h>
+#include <algorithm>
+#include "fpll_btloop_coupling.h"
+#include <gr_math.h>
+
+atsc_fpll_sptr
+atsc_make_fpll()
+{
+  return atsc_fpll_sptr(new atsc_fpll());
+}
+
+
+/*
+ * I strongly suggest that you not mess with these...
+ *
+ * They are strongly coupled into the symbol timing code and
+ * their value also sets the level of the symbols going
+ * into the equalizer and viterbi decoder.
+ */
+static const float FPLL_AGC_REFERENCE = 2.5 * FPLL_BTLOOP_COUPLING_CONST;
+static const float FPLL_AGC_RATE = 0.25e-6;
+
+
+
+atsc_fpll::atsc_fpll()
+  : gr_sync_block("atsc_fpll",
+		  gr_make_io_signature(1, 1, sizeof(float)),
+		  gr_make_io_signature(1, 1, sizeof(float))),
+		  initial_phase(0)
+{
+  initial_freq = 5.75e6 - 3e6 + 0.31e6 + 5e3; // a_initial_freq;
+  agc.set_rate (FPLL_AGC_RATE);
+  agc.set_reference (FPLL_AGC_REFERENCE);
+  initialize();
+}
+
+
+void
+atsc_fpll::initialize ()
+{
+  float Fs = 19.2e6;
+
+  float alpha = 1 - exp(-1.0 / Fs / 5e-6);
+
+  afci.set_taps (alpha);
+  afcq.set_taps (alpha);
+
+  printf("Setting initial_freq: %f\n",initial_freq);
+  nco.set_freq (initial_freq / Fs * 2 * M_PI);
+  nco.set_phase (initial_phase);
+}
+
+
+int
+atsc_fpll::work (int noutput_items,
+		       gr_vector_const_void_star &input_items,
+		       gr_vector_void_star &output_items)
+{
+  const float *in = (const float *) input_items[0];
+  float *out = (float *) output_items[0];
+
+  for (int k = 0; k < noutput_items; k++){
+
+    float a_cos, a_sin;
+
+    float input = agc.scale (in[k]);
+
+    nco.step ();                // increment phase
+    nco.sincos (&a_sin, &a_cos);  // compute cos and sin
+
+    float I = input * a_sin;
+    float Q = input * a_cos;
+
+    out[k] = I;
+
+    float filtered_I = afci.filter (I);
+    float filtered_Q = afcq.filter (Q);
+
+    // phase detector
+
+    // float x = atan2 (filtered_Q, filtered_I);
+    float x = gr_fast_atan2f(filtered_Q, filtered_I);
+
+    // avoid slamming filter with big transitions
+
+    static const float limit = M_PI / 2;
+
+    if (x > limit)
+      x = limit;
+    else if (x < -limit)
+      x = -limit;
+
+    // static const float alpha = 0.037;   // Max value
+    // static const float alpha = 0.005;   // takes about 5k samples to pull in, stddev = 323
+    // static const float alpha = 0.002;   // takes about 15k samples to pull in, stddev =  69
+                                           //  or about 120k samples on noisy data,
+    static const float alpha = 0.001;
+    static const float beta = alpha * alpha / 4;
+
+    nco.adjust_phase (alpha * x);
+    nco.adjust_freq (beta * x);
+
+  }
+
+  return noutput_items;
+}
+
+
+