3 * Copyright 2009 Free Software Foundation, Inc.
5 * This file is part of GNU Radio
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)
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.
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.
27 #include <gr_pfb_decimator_ccf.h>
28 #include <gr_fir_ccf.h>
29 #include <gr_fir_util.h>
31 #include <gr_io_signature.h>
34 gr_pfb_decimator_ccf_sptr gr_make_pfb_decimator_ccf (unsigned int decim,
35 const std::vector<float> &taps,
38 return gr_pfb_decimator_ccf_sptr (new gr_pfb_decimator_ccf (decim, taps, channel));
42 gr_pfb_decimator_ccf::gr_pfb_decimator_ccf (unsigned int decim,
43 const std::vector<float> &taps,
45 : gr_sync_block ("pfb_decimator_ccf",
46 gr_make_io_signature (decim, decim, sizeof(gr_complex)),
47 gr_make_io_signature (1, 1, sizeof(gr_complex))),
51 d_filters = std::vector<gr_fir_ccf*>(d_rate);
53 d_rotator = new gr_complex[d_rate];
55 // Create an FIR filter for each channel and zero out the taps
56 std::vector<float> vtaps(0, d_rate);
57 for(unsigned int i = 0; i < d_rate; i++) {
58 d_filters[i] = gr_fir_util::create_gr_fir_ccf(vtaps);
59 d_rotator[i] = gr_expj(i*2*M_PI*d_chan/d_rate);
62 // Now, actually set the filters' taps
65 // Create the FFT to handle the output de-spinning of the channels
66 d_fft = new gri_fft_complex (d_rate, false);
69 gr_pfb_decimator_ccf::~gr_pfb_decimator_ccf ()
71 for(unsigned int i = 0; i < d_rate; i++) {
77 gr_pfb_decimator_ccf::set_taps (const std::vector<float> &taps)
81 unsigned int ntaps = taps.size();
82 d_taps_per_filter = (unsigned int)ceil((double)ntaps/(double)d_rate);
84 // Create d_numchan vectors to store each channel's taps
85 d_taps.resize(d_rate);
87 // Make a vector of the taps plus fill it out with 0's to fill
88 // each polyphase filter with exactly d_taps_per_filter
89 std::vector<float> tmp_taps;
91 while((float)(tmp_taps.size()) < d_rate*d_taps_per_filter) {
92 tmp_taps.push_back(0.0);
95 // Partition the filter
96 for(i = 0; i < d_rate; i++) {
97 // Each channel uses all d_taps_per_filter with 0's if not enough taps to fill out
98 d_taps[i] = std::vector<float>(d_taps_per_filter, 0);
99 for(j = 0; j < d_taps_per_filter; j++) {
100 d_taps[i][j] = tmp_taps[i + j*d_rate]; // add taps to channels in reverse order
103 // Build a filter for each channel and add it's taps to it
104 d_filters[i]->set_taps(d_taps[i]);
107 // Set the history to ensure enough input items for each filter
108 set_history (d_taps_per_filter);
114 gr_pfb_decimator_ccf::print_taps()
117 for(i = 0; i < d_rate; i++) {
118 printf("filter[%d]: [", i);
119 for(j = 0; j < d_taps_per_filter; j++) {
120 printf(" %.4e", d_taps[i][j]);
129 gr_pfb_decimator_ccf::work (int noutput_items,
130 gr_vector_const_void_star &input_items,
131 gr_vector_void_star &output_items)
134 gr_complex *out = (gr_complex *) output_items[0];
138 return 0; // history requirements may have changed.
142 for(i = 0; i < noutput_items; i++) {
143 // Move through filters from bottom to top
145 for(int j = d_rate-1; j >= 0; j--) {
146 // Take in the items from the first input stream to d_rate
147 in = (gr_complex*)input_items[d_rate - 1 - j];
149 // Filter current input stream from bottom filter to top
150 // The rotate them by expj(j*k*2pi/M) where M is the number of filters
151 // (the decimation rate) and k is the channel number to extract
153 // This is the real math that goes on; we abuse the FFT to do this quickly
154 // for decimation rates > N where N is a small number (~5):
155 // out[i] += d_filters[j]->filter(&in[i])*gr_expj(j*d_chan*2*M_PI/d_rate);
157 d_fft->get_inbuf()[j] = d_filters[j]->filter(&in[i]);
159 out[i] += d_filters[j]->filter(&in[i])*d_rotator[i];
164 // Perform the FFT to do the complex multiply despinning for all channels
167 // Select only the desired channel out
168 out[i] = d_fft->get_outbuf()[d_chan];
173 return noutput_items;