GNU Radio 3.6.4 C++ API
gr_dc_blocker_ff.h
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/* -*- c++ -*- */
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/*
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* Copyright 2011 Free Software Foundation, Inc.
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*
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* This file is part of GNU Radio
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*
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* GNU Radio is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3, or (at your option)
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* any later version.
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*
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* GNU Radio is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU Radio; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#ifndef INCLUDED_GR_DC_BLOCKER_FF_H
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#define INCLUDED_GR_DC_BLOCKER_FF_H
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#include <
gr_core_api.h
>
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#include <
gr_sync_block.h
>
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#include <deque>
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class
GR_CORE_API
moving_averager_f
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{
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public
:
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moving_averager_f
(
int
D);
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~
moving_averager_f
();
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float
filter(
float
x);
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float
delayed_sig
() {
return
d_out; }
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private
:
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int
d_length;
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float
d_out, d_out_d1, d_out_d2;
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std::deque<float> d_delay_line;
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};
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class
gr_dc_blocker_ff
;
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typedef
boost::shared_ptr<gr_dc_blocker_ff>
gr_dc_blocker_ff_sptr
;
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GR_CORE_API
gr_dc_blocker_ff_sptr
gr_make_dc_blocker_ff
(
int
D=32,
bool
long_form=
true
);
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/*!
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* \class gr_dc_blocker_ff
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* \brief a computationally efficient controllable DC blocker
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*
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* \ingroup filter_blk
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*
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* This block implements a computationally efficient DC blocker that produces
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* a tighter notch filter around DC for a smaller group delay than an
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* equivalent FIR filter or using a single pole IIR filter (though the IIR
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* filter is computationally cheaper).
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*
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* The block defaults to using a delay line of length 32 and the long form
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* of the filter. Optionally, the delay line length can be changed to alter
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* the width of the DC notch (longer lines will decrease the width).
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*
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* The long form of the filter produces a nearly flat response outside of
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* the notch but at the cost of a group delay of 2D-2.
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*
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* The short form of the filter does not have as flat a response in the
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* passband but has a group delay of only D-1 and is cheaper to compute.
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*
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* The theory behind this block can be found in the paper:
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*
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* <B><EM>R. Yates, "DC Blocker Algorithms," IEEE Signal Processing Magazine,
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* Mar. 2008, pp 132-134.</EM></B>
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*/
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class
GR_CORE_API
gr_dc_blocker_ff
:
public
gr_sync_block
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{
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private
:
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/*!
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* Build the DC blocker.
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* \param D (int) the length of the delay line
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* \param long_form (bool) whether to use long (true, default) or short form
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*/
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friend
GR_CORE_API
gr_dc_blocker_ff_sptr
gr_make_dc_blocker_ff
(
int
D,
bool
long_form);
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int
d_length;
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bool
d_long_form;
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moving_averager_f
*d_ma_0;
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moving_averager_f
*d_ma_1;
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moving_averager_f
*d_ma_2;
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moving_averager_f
*d_ma_3;
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std::deque<float> d_delay_line;
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gr_dc_blocker_ff
(
int
D,
bool
long_form);
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public
:
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~
gr_dc_blocker_ff
();
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/*!
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* Get the blocker's group delay that is based on length of delay lines
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*/
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int
get_group_delay();
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//int set_length(int D);
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int
work
(
int
noutput_items,
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gr_vector_const_void_star
&input_items,
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gr_vector_void_star
&output_items);
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};
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#endif
gnuradio
gnuradio-core
src
lib
filter
gr_dc_blocker_ff.h
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