GNU Radio 3.5.3.2 C++ API
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00001 /* -*- c++ -*- */ 00002 /* 00003 * Copyright 2009,2010 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 00024 #ifndef INCLUDED_GR_PFB_CHANNELIZER_CCF_H 00025 #define INCLUDED_GR_PFB_CHANNELIZER_CCF_H 00026 00027 #include <gr_core_api.h> 00028 #include <gr_block.h> 00029 00030 class gr_pfb_channelizer_ccf; 00031 typedef boost::shared_ptr<gr_pfb_channelizer_ccf> gr_pfb_channelizer_ccf_sptr; 00032 GR_CORE_API gr_pfb_channelizer_ccf_sptr gr_make_pfb_channelizer_ccf (unsigned int numchans, 00033 const std::vector<float> &taps, 00034 float oversample_rate=1); 00035 00036 class gr_fir_ccf; 00037 class gri_fft_complex; 00038 00039 00040 /*! 00041 * \class gr_pfb_channelizer_ccf 00042 * 00043 * \brief Polyphase filterbank channelizer with 00044 * gr_complex input, gr_complex output and float taps 00045 * 00046 * \ingroup filter_blk 00047 * \ingroup pfb_blk 00048 * 00049 * This block takes in complex inputs and channelizes it to <EM>M</EM> 00050 * channels of equal bandwidth. Each of the resulting channels is 00051 * decimated to the new rate that is the input sampling rate 00052 * <EM>fs</EM> divided by the number of channels, <EM>M</EM>. 00053 * 00054 * The PFB channelizer code takes the taps generated above and builds 00055 * a set of filters. The set contains <EM>M</EM> number of filters 00056 * and each filter contains ceil(taps.size()/decim) number of taps. 00057 * Each tap from the filter prototype is sequentially inserted into 00058 * the next filter. When all of the input taps are used, the remaining 00059 * filters in the filterbank are filled out with 0's to make sure each 00060 * filter has the same number of taps. 00061 * 00062 * Each filter operates using the gr_fir filter classs of GNU Radio, 00063 * which takes the input stream at <EM>i</EM> and performs the inner 00064 * product calculation to <EM>i+(n-1)</EM> where <EM>n</EM> is the 00065 * number of filter taps. To efficiently handle this in the GNU Radio 00066 * structure, each filter input must come from its own input 00067 * stream. So the channelizer must be provided with <EM>M</EM> streams 00068 * where the input stream has been deinterleaved. This is most easily 00069 * done using the gr_stream_to_streams block. 00070 * 00071 * The output is then produced as a vector, where index <EM>i</EM> in 00072 * the vector is the next sample from the <EM>i</EM>th channel. This 00073 * is most easily handled by sending the output to a 00074 * gr_vector_to_streams block to handle the conversion and passing 00075 * <EM>M</EM> streams out. 00076 * 00077 * The input and output formatting is done using a hier_block2 called 00078 * pfb_channelizer_ccf. This can take in a single stream and outputs 00079 * <EM>M</EM> streams based on the behavior described above. 00080 * 00081 * The filter's taps should be based on the input sampling rate. 00082 * 00083 * For example, using the GNU Radio's firdes utility to building 00084 * filters, we build a low-pass filter with a sampling rate of 00085 * <EM>fs</EM>, a 3-dB bandwidth of <EM>BW</EM> and a transition 00086 * bandwidth of <EM>TB</EM>. We can also specify the out-of-band 00087 * attenuation to use, <EM>ATT</EM>, and the filter window 00088 * function (a Blackman-harris window in this case). The first input 00089 * is the gain of the filter, which we specify here as unity. 00090 * 00091 * <B><EM>self._taps = gr.firdes.low_pass_2(1, fs, BW, TB, 00092 * attenuation_dB=ATT, window=gr.firdes.WIN_BLACKMAN_hARRIS)</EM></B> 00093 * 00094 * The filter output can also be overs ampled. The over sampling rate 00095 * is the ratio of the the actual output sampling rate to the normal 00096 * output sampling rate. It must be rationally related to the number 00097 * of channels as N/i for i in [1,N], which gives an outputsample rate 00098 * of [fs/N, fs] where fs is the input sample rate and N is the number 00099 * of channels. 00100 * 00101 * For example, for 6 channels with fs = 6000 Hz, the normal rate is 00102 * 6000/6 = 1000 Hz. Allowable oversampling rates are 6/6, 6/5, 6/4, 00103 * 6/3, 6/2, and 6/1 where the output sample rate of a 6/1 oversample 00104 * ratio is 6000 Hz, or 6 times the normal 1000 Hz. A rate of 6/5 = 1.2, 00105 * so the output rate would be 1200 Hz. 00106 * 00107 * The theory behind this block can be found in Chapter 6 of 00108 * the following book. 00109 * 00110 * <B><EM>f. harris, "Multirate Signal Processing for Communication 00111 * Systems," Upper Saddle River, NJ: Prentice Hall, Inc. 2004.</EM></B> 00112 * 00113 */ 00114 00115 class GR_CORE_API gr_pfb_channelizer_ccf : public gr_block 00116 { 00117 private: 00118 /*! 00119 * Build the polyphase filterbank decimator. 00120 * \param numchans (unsigned integer) Specifies the number of channels <EM>M</EM> 00121 * \param taps (vector/list of floats) The prototype filter to populate the filterbank. 00122 * \param oversample_rate (float) The over sampling rate is the ratio of the the actual 00123 * output sampling rate to the normal output sampling rate. 00124 * It must be rationally related to the number of channels 00125 * as N/i for i in [1,N], which gives an outputsample rate 00126 * of [fs/N, fs] where fs is the input sample rate and N is 00127 * the number of channels. 00128 * 00129 * For example, for 6 channels with fs = 6000 Hz, the normal 00130 * rate is 6000/6 = 1000 Hz. Allowable oversampling rates 00131 * are 6/6, 6/5, 6/4, 6/3, 6/2, and 6/1 where the output 00132 * sample rate of a 6/1 oversample ratio is 6000 Hz, or 00133 * 6 times the normal 1000 Hz. 00134 */ 00135 friend GR_CORE_API gr_pfb_channelizer_ccf_sptr gr_make_pfb_channelizer_ccf (unsigned int numchans, 00136 const std::vector<float> &taps, 00137 float oversample_rate); 00138 00139 bool d_updated; 00140 unsigned int d_numchans; 00141 float d_oversample_rate; 00142 std::vector<gr_fir_ccf*> d_filters; 00143 std::vector< std::vector<float> > d_taps; 00144 unsigned int d_taps_per_filter; 00145 gri_fft_complex *d_fft; 00146 int *d_idxlut; 00147 int d_rate_ratio; 00148 int d_output_multiple; 00149 00150 /*! 00151 * Build the polyphase filterbank decimator. 00152 * \param numchans (unsigned integer) Specifies the number of channels <EM>M</EM> 00153 * \param taps (vector/list of floats) The prototype filter to populate the filterbank. 00154 * \param oversample_rate (float) The output over sampling rate. 00155 */ 00156 gr_pfb_channelizer_ccf (unsigned int numchans, 00157 const std::vector<float> &taps, 00158 float oversample_rate); 00159 00160 public: 00161 ~gr_pfb_channelizer_ccf (); 00162 00163 /*! 00164 * Resets the filterbank's filter taps with the new prototype filter 00165 * \param taps (vector/list of floats) The prototype filter to populate the filterbank. 00166 */ 00167 void set_taps (const std::vector<float> &taps); 00168 00169 /*! 00170 * Print all of the filterbank taps to screen. 00171 */ 00172 void print_taps(); 00173 00174 int general_work (int noutput_items, 00175 gr_vector_int &ninput_items, 00176 gr_vector_const_void_star &input_items, 00177 gr_vector_void_star &output_items); 00178 }; 00179 00180 #endif