GNU Radio v3.6.2-149-ga6d285d9 C++ API
mmse_fir_interpolator_ff.h
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00001 /* -*- c++ -*- */
00002 /*
00003  * Copyright 2002,2012 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 
00023 #ifndef _MMSE_FIR_INTERPOLATOR_FF_H_
00024 #define _MMSE_FIR_INTERPOLATOR_FF_H_
00025 
00026 #include <filter/api.h>
00027 #include <filter/fir_filter.h>
00028 #include <vector>
00029 
00030 namespace gr {
00031   namespace filter {
00032     
00033     /*!
00034      * \brief Compute intermediate samples between signal samples x(k*Ts)
00035      * \ingroup filter_primitive
00036      *
00037      * This implements a Mininum Mean Squared Error interpolator with
00038      * 8 taps. It is suitable for signals where the bandwidth of
00039      * interest B = 1/(4*Ts) Where Ts is the time between samples.
00040      *
00041      * Although mu, the fractional delay, is specified as a float, it
00042      * is actually quantized. 0.0 <= mu <= 1.0. That is, mu is
00043      * quantized in the interpolate method to 32nd's of a sample.
00044      *
00045      * For more information, in the GNU Radio source code, see:
00046      * \li gnuradio-core/src/gen_interpolator_taps/README
00047      * \li gnuradio-core/src/gen_interpolator_taps/praxis.txt
00048      */
00049     class FILTER_API mmse_fir_interpolator_ff
00050     {
00051     public:
00052       mmse_fir_interpolator_ff();
00053       ~mmse_fir_interpolator_ff();
00054 
00055       unsigned ntaps() const;
00056       unsigned nsteps() const;
00057 
00058       /*!
00059        * \brief compute a single interpolated output value.
00060        * \p input must have ntaps() valid entries.
00061        * input[0] .. input[ntaps() - 1] are referenced to compute the output value.
00062        *
00063        * \p mu must be in the range [0, 1] and specifies the fractional delay.
00064        *
00065        * \returns the interpolated input value.
00066        */
00067       float interpolate(const float input[], float mu) const;
00068 
00069     protected:
00070       std::vector<kernel::fir_filter_fff*> filters;
00071     };
00072 
00073   }  /* namespace filter */
00074 }  /* namespace gr */
00075 
00076 #endif /* _MMSE_FIR_INTERPOLATOR_FF_H_ */