GNU Radio C++ API
gr_pfb_decimator_ccf.h
Go to the documentation of this file.
1
/* -*- c++ -*- */
2
/*
3
* Copyright 2009 Free Software Foundation, Inc.
4
*
5
* This file is part of GNU Radio
6
*
7
* GNU Radio is free software; you can redistribute it and/or modify
8
* it under the terms of the GNU General Public License as published by
9
* the Free Software Foundation; either version 3, or (at your option)
10
* any later version.
11
*
12
* GNU Radio is distributed in the hope that it will be useful,
13
* but WITHOUT ANY WARRANTY; without even the implied warranty of
14
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15
* GNU General Public License for more details.
16
*
17
* You should have received a copy of the GNU General Public License
18
* along with GNU Radio; see the file COPYING. If not, write to
19
* the Free Software Foundation, Inc., 51 Franklin Street,
20
* Boston, MA 02110-1301, USA.
21
*/
22
23
24
#ifndef INCLUDED_GR_PFB_DECIMATOR_CCF_H
25
#define INCLUDED_GR_PFB_DECIMATOR_CCF_H
26
27
#include <
gr_core_api.h
>
28
#include <
gr_sync_block.h
>
29
30
class
gr_pfb_decimator_ccf
;
31
typedef
boost::shared_ptr<gr_pfb_decimator_ccf>
gr_pfb_decimator_ccf_sptr
;
32
GR_CORE_API
gr_pfb_decimator_ccf_sptr
gr_make_pfb_decimator_ccf
(
unsigned
int
decim,
33
const
std::vector<float> &
taps
,
34
unsigned
int
channel=0);
35
36
class
gr_fir_ccf
;
37
class
gri_fft_complex
;
38
39
/*!
40
* \class gr_pfb_decimator_ccf
41
* \brief Polyphase filterbank bandpass decimator with gr_complex
42
* input, gr_complex output and float taps
43
*
44
* \ingroup filter_blk
45
* \ingroup pfb_blk
46
*
47
* This block takes in a signal stream and performs interger down-
48
* sampling (decimation) with a polyphase filterbank. The first input
49
* is the integer specifying how much to decimate by. The second
50
* input is a vector (Python list) of floating-point taps of the
51
* prototype filter. The third input specifies the channel to extract.
52
* By default, the zeroth channel is used, which is the baseband
53
* channel (first Nyquist zone).
54
*
55
* The <EM>channel</EM> parameter specifies which channel to use since
56
* this class is capable of bandpass decimation. Given a complex input
57
* stream at a sampling rate of <EM>fs</EM> and a decimation rate of
58
* <EM>decim</EM>, the input frequency domain is split into
59
* <EM>decim</EM> channels that represent the Nyquist zones. Using the
60
* polyphase filterbank, we can select any one of these channels to
61
* decimate.
62
*
63
* The output signal will be the basebanded and decimated signal from
64
* that channel. This concept is very similar to the PFB channelizer
65
* (see #gr_pfb_channelizer_ccf) where only a single channel is
66
* extracted at a time.
67
*
68
* The filter's taps should be based on the sampling rate before
69
* decimation.
70
*
71
* For example, using the GNU Radio's firdes utility to building
72
* filters, we build a low-pass filter with a sampling rate of
73
* <EM>fs</EM>, a 3-dB bandwidth of <EM>BW</EM> and a transition
74
* bandwidth of <EM>TB</EM>. We can also specify the out-of-band
75
* attenuation to use, <EM>ATT</EM>, and the filter window
76
* function (a Blackman-harris window in this case). The first input
77
* is the gain of the filter, which we specify here as unity.
78
*
79
* <B><EM>self._taps = gr.firdes.low_pass_2(1, fs, BW, TB,
80
* attenuation_dB=ATT, window=gr.firdes.WIN_BLACKMAN_hARRIS)</EM></B>
81
*
82
* The PFB decimator code takes the taps generated above and builds a
83
* set of filters. The set contains <EM>decim</EM> number of filters
84
* and each filter contains ceil(taps.size()/decim) number of taps.
85
* Each tap from the filter prototype is sequentially inserted into
86
* the next filter. When all of the input taps are used, the remaining
87
* filters in the filterbank are filled out with 0's to make sure each
88
* filter has the same number of taps.
89
*
90
* The theory behind this block can be found in Chapter 6 of
91
* the following book.
92
*
93
* <B><EM>f. harris, "Multirate Signal Processing for Communication
94
* Systems," Upper Saddle River, NJ: Prentice Hall, Inc. 2004.</EM></B>
95
*/
96
97
class
GR_CORE_API
gr_pfb_decimator_ccf
:
public
gr_sync_block
98
{
99
private
:
100
/*!
101
* Build the polyphase filterbank decimator.
102
* \param decim (unsigned integer) Specifies the decimation rate to use
103
* \param taps (vector/list of floats) The prototype filter to populate the filterbank.
104
* \param channel (unsigned integer) Selects the channel to return [default=0].
105
*/
106
friend
GR_CORE_API
gr_pfb_decimator_ccf_sptr
gr_make_pfb_decimator_ccf
(
unsigned
int
decim,
107
const
std::vector<float> &
taps
,
108
unsigned
int
channel);
109
110
std::vector<gr_fir_ccf*> d_filters;
111
std::vector< std::vector<float> > d_taps;
112
gri_fft_complex
*d_fft;
113
unsigned
int
d_rate;
114
unsigned
int
d_chan;
115
unsigned
int
d_taps_per_filter;
116
bool
d_updated;
117
gr_complex
*d_rotator;
118
119
/*!
120
* Build the polyphase filterbank decimator.
121
* \param decim (unsigned integer) Specifies the decimation rate to use
122
* \param taps (vector/list of floats) The prototype filter to populate the filterbank.
123
* \param channel (unsigned integer) Selects the channel to return [default=0].
124
*/
125
gr_pfb_decimator_ccf
(
unsigned
int
decim,
126
const
std::vector<float> &taps,
127
unsigned
int
channel);
128
129
public
:
130
~
gr_pfb_decimator_ccf
();
131
132
/*!
133
* Resets the filterbank's filter taps with the new prototype filter
134
* \param taps (vector/list of floats) The prototype filter to populate the filterbank.
135
*/
136
void
set_taps (
const
std::vector<float> &taps);
137
138
/*!
139
* Print all of the filterbank taps to screen.
140
*/
141
void
print_taps();
142
143
//void set_channel (unsigned int channel);
144
145
int
work
(
int
noutput_items,
146
gr_vector_const_void_star
&input_items,
147
gr_vector_void_star
&output_items);
148
};
149
150
#endif
gnuradio-core
src
lib
filter
gr_pfb_decimator_ccf.h
Generated on Wed Jul 11 2012 23:41:33 for GNU Radio C++ API by
1.8.1.1