GNU Radio 3.5.1 C++ API
gri_mmse_fir_interpolator.h
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00001 /* -*- c++ -*- */
00002 /*
00003  * Copyright 2002 Free Software Foundation, Inc.
00004  * 
00005  * This file is part of GNU Radio
00006  * 
00007  * GNU Radio is free software; you can redistribute it and/or modify
00008  * it under the terms of the GNU General Public License as published by
00009  * the Free Software Foundation; either version 3, or (at your option)
00010  * any later version.
00011  * 
00012  * GNU Radio is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  * GNU General Public License for more details.
00016  * 
00017  * You should have received a copy of the GNU General Public License
00018  * along with GNU Radio; see the file COPYING.  If not, write to
00019  * the Free Software Foundation, Inc., 51 Franklin Street,
00020  * Boston, MA 02110-1301, USA.
00021  */
00022 #ifndef _GRI_MMSE_FIR_INTERPOLATOR_H_
00023 #define _GRI_MMSE_FIR_INTERPOLATOR_H_
00024 
00025 #include <gr_core_api.h>
00026 #include <vector>
00027 
00028 class gr_fir_fff;
00029 
00030 /*!
00031  * \brief Compute intermediate samples between signal samples x(k*Ts)
00032  * \ingroup filter_primitive
00033  *
00034  * This implements a Mininum Mean Squared Error interpolator with 8 taps.
00035  * It is suitable for signals where the bandwidth of interest B = 1/(4*Ts)
00036  * Where Ts is the time between samples.
00037  *
00038  * Although mu, the fractional delay, is specified as a float, it is actually
00039  * quantized.  0.0 <= mu <= 1.0.  That is, mu is quantized in the interpolate 
00040  * method to 32nd's of a sample.
00041  */
00042 
00043 class GR_CORE_API gri_mmse_fir_interpolator {
00044 public:
00045   gri_mmse_fir_interpolator ();
00046   ~gri_mmse_fir_interpolator ();
00047 
00048   unsigned ntaps () const;
00049   unsigned nsteps () const;
00050 
00051   /*!
00052    * \brief compute a single interpolated output value.
00053    * \p input must have ntaps() valid entries.
00054    * input[0] .. input[ntaps() - 1] are referenced to compute the output value.
00055    *
00056    * \p mu must be in the range [0, 1] and specifies the fractional delay.
00057    *
00058    * \returns the interpolated input value.
00059    */
00060   float interpolate (const float input[], float mu) const;
00061 
00062 protected:
00063   std::vector<gr_fir_fff *>     filters;
00064 };
00065 
00066 
00067 #endif /* _GRI_MMSE_FIR_INTERPOLATOR_H_ */