GNU Radio Manual and C++ API Reference 3.7.14.0
The Free & Open Software Radio Ecosystem
pfb_channelizer_ccf.h
Go to the documentation of this file.
1/* -*- c++ -*- */
2/*
3 * Copyright 2009,2010,2012 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_FILTER_PFB_CHANNELIZER_CCF_H
25#define INCLUDED_FILTER_PFB_CHANNELIZER_CCF_H
26
27#include <gnuradio/block.h>
28#include <gnuradio/filter/api.h>
29
30namespace gr {
31namespace filter {
32
33/*!
34 * \brief Polyphase filterbank channelizer with
35 * gr_complex input, gr_complex output and float taps
36 * \ingroup channelizers_blk
37 *
38 * \details
39 * This block takes in complex inputs and channelizes it to <EM>M</EM>
40 * channels of equal bandwidth. Each of the resulting channels is
41 * decimated to the new rate that is the input sampling rate
42 * <EM>fs</EM> divided by the number of channels, <EM>M</EM>.
43 *
44 * The PFB channelizer code takes the taps generated above and builds
45 * a set of filters. The set contains <EM>M</EM>filters
46 * and each filter contains ceil(taps.size()/decim) taps.
47 * Each tap from the filter prototype is sequentially inserted into
48 * the next filter. When all of the input taps are used, the remaining
49 * filters in the filterbank are filled out with 0's to make sure each
50 * filter has the same number of taps.
51 *
52 * Each filter operates using the gr::blocks::fir_filter_XXX
53 * class of GNU Radio, which takes the input stream at <EM>i</EM>
54 * and performs the inner product calculation to <EM>i+(n-1)</EM>
55 * where <EM>n</EM> is the number of filter taps. To efficiently
56 * handle this in the GNU Radio structure, each filter input must
57 * come from its own input stream. So the channelizer must be
58 * provided with <EM>M</EM> streams where the input stream has
59 * been deinterleaved. This is most easily done using the
60 * gr::blocks::stream_to_streams block.
61 *
62 * The output is then produced as a vector, where index <EM>i</EM>
63 * in the vector is the next sample from the <EM>i</EM>th
64 * channel. This is most easily handled by sending the output to a
65 * gr::blocks::vector_to_streams block to handle the conversion
66 * and passing <EM>M</EM> streams out.
67 *
68 * The input and output formatting is done using a hier_block2 called
69 * pfb_channelizer_ccf. This can take in a single stream and outputs
70 * <EM>M</EM> streams based on the behavior described above.
71 *
72 * The filter's taps should be based on the input sampling rate.
73 *
74 * For example, using the GNU Radio's firdes utility to building
75 * filters, we build a low-pass filter with a sampling rate of
76 * <EM>fs</EM>, a 3-dB bandwidth of <EM>BW</EM> and a transition
77 * bandwidth of <EM>TB</EM>. We can also specify the out-of-band
78 * attenuation to use, <EM>ATT</EM>, and the filter window
79 * function (a Blackman-harris window in this case). The first input
80 * is the gain of the filter, which we specify here as unity.
81 *
82 * <B><EM>self._taps = filter.firdes.low_pass_2(1, fs, BW, TB,
83 * attenuation_dB=ATT, window=filter.firdes.WIN_BLACKMAN_hARRIS)</EM></B>
84 *
85 * The filter output can also be oversampled. The oversampling rate
86 * is the ratio of the the actual output sampling rate to the normal
87 * output sampling rate. It must be rationally related to the number
88 * of channels as N/i for i in [1,N], which gives an outputsample rate
89 * of [fs/N, fs] where fs is the input sample rate and N is the number
90 * of channels.
91 *
92 * For example, for 6 channels with fs = 6000 Hz, the normal rate is
93 * 6000/6 = 1000 Hz. Allowable oversampling rates are 6/6, 6/5, 6/4,
94 * 6/3, 6/2, and 6/1 where the output sample rate of a 6/1 oversample
95 * ratio is 6000 Hz, or 6 times the normal 1000 Hz. A rate of 6/5 = 1.2,
96 * so the output rate would be 1200 Hz.
97 *
98 * The theory behind this block can be found in Chapter 6 of
99 * the following book:
100 *
101 * <B><EM>f. harris, "Multirate Signal Processing for Communication
102 * Systems," Upper Saddle River, NJ: Prentice Hall, Inc. 2004.</EM></B>
103 *
104 * When dealing with oversampling, the above book is still a good
105 * reference along with this paper:
106 *
107 * <B><EM>E. Venosa, X. Chen, and fred harris, “Polyphase analysis
108 * filter bank down-converts unequal channel bandwidths with
109 * arbitrary center frequencies - design I,” in SDR’10-WinnComm,
110 * 2010.</EM></B>
111 */
113{
114public:
115 // gr::filter::pfb_channelizer_ccf::sptr
116 typedef boost::shared_ptr<pfb_channelizer_ccf> sptr;
117
118 /*!
119 * Build the polyphase filterbank decimator.
120 * \param numchans (unsigned integer) Specifies the number of
121 * channels <EM>M</EM>
122 * \param taps (vector/list of floats) The prototype filter to
123 * populate the filterbank.
124 * \param oversample_rate (float) The oversampling rate is the
125 * ratio of the the actual output
126 * sampling rate to the normal
127 * output sampling rate. It must
128 * be rationally related to the
129 * number of channels as N/i for
130 * i in [1,N], which gives an
131 * outputsample rate of [fs/N,
132 * fs] where fs is the input
133 * sample rate and N is the
134 * number of channels.
135 *
136 * For example, for 6 channels
137 * with fs = 6000 Hz, the normal
138 * rate is 6000/6 = 1000
139 * Hz. Allowable oversampling
140 * rates are 6/6, 6/5, 6/4, 6/3,
141 * 6/2, and 6/1 where the output
142 * sample rate of a 6/1
143 * oversample ratio is 6000 Hz,
144 * or 6 times the normal 1000 Hz.
145 */
146 static sptr
147 make(unsigned int numchans, const std::vector<float>& taps, float oversample_rate);
148
149 /*!
150 * Resets the filterbank's filter taps with the new prototype filter
151 * \param taps (vector/list of floats) The prototype filter to populate the
152 * filterbank.
153 */
154 virtual void set_taps(const std::vector<float>& taps) = 0;
155
156 /*!
157 * Print all of the filterbank taps to screen.
158 */
159 virtual void print_taps() = 0;
160
161 /*!
162 * Return a vector<vector<>> of the filterbank taps
163 */
164 virtual std::vector<std::vector<float> > taps() const = 0;
165
166 /*!
167 * Set the channel map. Channels are numbers as:
168 * <pre>
169 * N/2+1 | ... | N-1 | 0 | 1 | 2 | ... | N/2
170 * <------------------- 0 -------------------->
171 * freq
172 * </pre>
173 *
174 * So output stream 0 comes from channel 0, etc. Setting a new
175 * channel map allows the user to specify which channel in frequency
176 * he/she wants to got to which output stream.
177 *
178 * The map should have the same number of elements as the number
179 * of output connections from the block. The minimum value of
180 * the map is 0 (for the 0th channel) and the maximum number is
181 * N-1 where N is the number of channels.
182 *
183 * We specify M as the number of output connections made where M
184 * <= N, so only M out of N channels are driven to an output
185 * stream. The number of items in the channel map should be at
186 * least M long. If there are more channels specified, any value
187 * in the map over M-1 will be ignored. If the size of the map
188 * is less than M the behavior is unknown (we don't wish to
189 * check every entry into the work function).
190 *
191 * This means that if the channelizer is splitting the signal up
192 * into N channels but only M channels are specified in the map
193 * (where M <= N), then M output streams must be connected and
194 * the map and the channel numbers used must be less than
195 * N-1. Output channel number can be reused, too. By default,
196 * the map is [0...M-1] with M = N.
197 */
198 virtual void set_channel_map(const std::vector<int>& map) = 0;
199
200 /*!
201 * Gets the current channel map.
202 */
203 virtual std::vector<int> channel_map() const = 0;
204};
205
206} /* namespace filter */
207} /* namespace gr */
208
209#endif /* INCLUDED_FILTER_PFB_CHANNELIZER_CCF_H */
The abstract base class for all 'terminal' processing blocks.
Definition: block.h:66
Polyphase filterbank channelizer with gr_complex input, gr_complex output and float taps.
Definition: pfb_channelizer_ccf.h:113
boost::shared_ptr< pfb_channelizer_ccf > sptr
Definition: pfb_channelizer_ccf.h:116
static sptr make(unsigned int numchans, const std::vector< float > &taps, float oversample_rate)
virtual void set_channel_map(const std::vector< int > &map)=0
virtual void set_taps(const std::vector< float > &taps)=0
virtual std::vector< int > channel_map() const =0
virtual std::vector< std::vector< float > > taps() const =0
#define FILTER_API
Definition: gr-filter/include/gnuradio/filter/api.h:30
static const float taps[NSTEPS+1][NTAPS]
Definition: interpolator_taps.h:9
Include this header to use the message passing features.
Definition: basic_block.h:45
PMT_API pmt_t map(pmt_t proc(const pmt_t &), pmt_t list)
Apply proc element-wise to the elements of list and returns a list of the results,...