GNU Radio 3.5.3.2 C++ API
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00001 /* -*- c++ -*- */ 00002 /* 00003 * Copyright 2004 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 INCLUDED_GR_IIR_FILTER_FFD_H 00024 #define INCLUDED_GR_IIR_FILTER_FFD_H 00025 00026 #include <gr_core_api.h> 00027 #include <gr_sync_block.h> 00028 #include <gri_iir.h> 00029 #include <stdexcept> 00030 00031 class gr_iir_filter_ffd; 00032 typedef boost::shared_ptr<gr_iir_filter_ffd> gr_iir_filter_ffd_sptr; 00033 GR_CORE_API gr_iir_filter_ffd_sptr 00034 gr_make_iir_filter_ffd (const std::vector<double> &fftaps, 00035 const std::vector<double> &fbtaps) throw (std::invalid_argument); 00036 00037 /*! 00038 * \brief IIR filter with float input, float output and double taps 00039 * \ingroup filter_blk 00040 * 00041 * This filter uses the Direct Form I implementation, where 00042 * \p fftaps contains the feed-forward taps, and \p fbtaps the feedback ones. 00043 * 00044 * 00045 * The input and output satisfy a difference equation of the form 00046 \htmlonly 00047 \f{ 00048 y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k] 00049 \f} 00050 \endhtmlonly 00051 00052 \xmlonly 00053 y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k] 00054 \endxmlonly 00055 00056 * with the corresponding rational system function 00057 \htmlonly 00058 \f{ 00059 H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}} 00060 \f} 00061 \endhtmlonly 00062 00063 \xmlonly 00064 H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}} 00065 \endxmlonly 00066 00067 * Note that some texts define the system function with a + in the denominator. 00068 * If you're using that convention, you'll need to negate the feedback taps. 00069 */ 00070 class GR_CORE_API gr_iir_filter_ffd : public gr_sync_block 00071 { 00072 private: 00073 friend GR_CORE_API gr_iir_filter_ffd_sptr 00074 gr_make_iir_filter_ffd (const std::vector<double> &fftaps, 00075 const std::vector<double> &fbtaps) throw (std::invalid_argument); 00076 00077 gri_iir<float,float,double> d_iir; 00078 std::vector<double> d_new_fftaps; 00079 std::vector<double> d_new_fbtaps; 00080 bool d_updated; 00081 00082 /*! 00083 * Construct an IIR filter with the given taps 00084 */ 00085 gr_iir_filter_ffd (const std::vector<double> &fftaps, 00086 const std::vector<double> &fbtaps) throw (std::invalid_argument); 00087 00088 public: 00089 ~gr_iir_filter_ffd (); 00090 00091 void set_taps (const std::vector<double> &fftaps, 00092 const std::vector<double> &fbtaps) throw (std::invalid_argument); 00093 00094 int work (int noutput_items, 00095 gr_vector_const_void_star &input_items, 00096 gr_vector_void_star &output_items); 00097 }; 00098 00099 #endif