1 files changed, 99 insertions, 0 deletions
diff --git a/gr-analog/lib/feedforward_agc_cc_impl.cc b/gr-analog/lib/feedforward_agc_cc_impl.cc
new file mode 100644
index 000000000..4796fdfc5
--- /dev/null
+++ b/gr-analog/lib/feedforward_agc_cc_impl.cc
@@ -0,0 +1,99 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2006,2010,2012 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 "feedforward_agc_cc_impl.h"
+#include <gr_io_signature.h>
+#include <stdexcept>
+
+namespace gr {
+  namespace analog {
+
+    feedforward_agc_cc::sptr
+    feedforward_agc_cc::make(int nsamples, float reference)
+    {
+      return gnuradio::get_initial_sptr
+	(new feedforward_agc_cc_impl(nsamples, reference));
+    }
+
+    feedforward_agc_cc_impl::feedforward_agc_cc_impl(int nsamples, float reference)
+      : gr_sync_block("feedforward_agc_cc",
+		      gr_make_io_signature(1, 1, sizeof(gr_complex)),
+		      gr_make_io_signature(1, 1, sizeof(gr_complex))),
+	d_nsamples(nsamples), d_reference(reference)
+    {
+      if(nsamples < 1)
+	throw std::invalid_argument("feedforward_agc_cc_impl: nsamples must be >= 1");
+  
+      set_history(nsamples);
+    }
+
+    feedforward_agc_cc_impl::~feedforward_agc_cc_impl()
+    {
+    }
+
+    inline static float
+    mag_squared(gr_complex x)
+    {
+      return x.real() * x.real() + x.imag() * x.imag();
+    }
+
+    // approximate sqrt(x^2 + y^2)
+    inline static float
+    envelope(gr_complex x)
+    {
+      float r_abs = std::fabs(x.real());
+      float i_abs = std::fabs(x.imag());
+
+      if(r_abs > i_abs)
+	return r_abs + 0.4 * i_abs;
+      else
+	return i_abs + 0.4 * r_abs;
+    }
+
+    int
+    feedforward_agc_cc_impl::work(int noutput_items,
+				  gr_vector_const_void_star &input_items,
+				  gr_vector_void_star &output_items)
+    {
+      const gr_complex *in = (const gr_complex*)input_items[0];
+      gr_complex *out = (gr_complex*)output_items[0];
+      int nsamples = d_nsamples;
+      float gain;
+
+      for(int i = 0; i < noutput_items; i++) {
+	//float max_env = 1e-12;	// avoid divide by zero
+	float max_env = 1e-4;	// avoid divide by zero, indirectly set max gain
+	for(int j = 0; j < nsamples; j++) {
+	  max_env = std::max(max_env, envelope(in[i+j]));
+	}
+	gain = d_reference / max_env;
+	out[i] = gain * in[i];
+      }
+      return noutput_items;
+    }
+
+  } /* namespace analog */
+} /* namespace gr */