GNU Radio v3.6.2-149-ga6d285d9 C++ API
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00001 /* -*- c++ -*- */ 00002 /* 00003 * Copyright 2011,2012 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 INCLUDED_FILTER_DC_BLOCKER_FF_H 00024 #define INCLUDED_FILTER_DC_BLOCKER_FF_H 00025 00026 #include <filter/api.h> 00027 #include <gr_sync_block.h> 00028 00029 namespace gr { 00030 namespace filter { 00031 00032 class FILTER_API dc_blocker_ff : virtual public gr_sync_block 00033 { 00034 public: 00035 00036 // gr::filter::dc_blocker_ff::sptr 00037 typedef boost::shared_ptr<dc_blocker_ff> sptr; 00038 00039 /*! 00040 * \class dc_blocker_ff 00041 * \brief a computationally efficient controllable DC blocker 00042 * 00043 * \ingroup filter_blk 00044 * 00045 * This block implements a computationally efficient DC blocker that produces 00046 * a tighter notch filter around DC for a smaller group delay than an 00047 * equivalent FIR filter or using a single pole IIR filter (though the IIR 00048 * filter is computationally cheaper). 00049 * 00050 * The block defaults to using a delay line of length 32 and the long form 00051 * of the filter. Optionally, the delay line length can be changed to alter 00052 * the width of the DC notch (longer lines will decrease the width). 00053 * 00054 * The long form of the filter produces a nearly flat response outside of 00055 * the notch but at the cost of a group delay of 2D-2. 00056 * 00057 * The short form of the filter does not have as flat a response in the 00058 * passband but has a group delay of only D-1 and is cheaper to compute. 00059 * 00060 * The theory behind this block can be found in the paper: 00061 * 00062 * <B><EM>R. Yates, "DC Blocker Algorithms," IEEE Signal Processing Magazine, 00063 * Mar. 2008, pp 132-134.</EM></B> 00064 * 00065 * \param D (int) the length of the delay line 00066 * \param long_form (bool) whether to use long (true, default) or short form 00067 */ 00068 static sptr make(int D, bool long_form=true); 00069 00070 virtual int group_delay() = 0; 00071 }; 00072 00073 } /* namespace filter */ 00074 } /* namespace gr */ 00075 00076 #endif /* INCLUDED_FILTER_DC_BLOCKER_FF_H */