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24 #ifndef INCLUDED_GR_PFB_CHANNELIZER_CCF_H
25 #define INCLUDED_GR_PFB_CHANNELIZER_CCF_H
29 class gr_pfb_channelizer_ccf;
30 typedef boost::shared_ptr<gr_pfb_channelizer_ccf> gr_pfb_channelizer_ccf_sptr;
31 gr_pfb_channelizer_ccf_sptr gr_make_pfb_channelizer_ccf (unsigned int numchans,
32 const std::vector<float> &taps,
33 float oversample_rate=1);
36 class gri_fft_complex;
40 * \class gr_pfb_channelizer_ccf
42 * \brief Polyphase filterbank channelizer with
43 * gr_complex input, gr_complex output and float taps
47 * This block takes in complex inputs and channelizes it to <EM>M</EM>
48 * channels of equal bandwidth. Each of the resulting channels is
49 * decimated to the new rate that is the input sampling rate
50 * <EM>fs</EM> divided by the number of channels, <EM>M</EM>.
52 * The PFB channelizer code takes the taps generated above and builds
53 * a set of filters. The set contains <EM>M</EM> number of filters
54 * and each filter contains ceil(taps.size()/decim) number of taps.
55 * Each tap from the filter prototype is sequentially inserted into
56 * the next filter. When all of the input taps are used, the remaining
57 * filters in the filterbank are filled out with 0's to make sure each
58 * filter has the same number of taps.
60 * Each filter operates using the gr_fir filter classs of GNU Radio,
61 * which takes the input stream at <EM>i</EM> and performs the inner
62 * product calculation to <EM>i+(n-1)</EM> where <EM>n</EM> is the
63 * number of filter taps. To efficiently handle this in the GNU Radio
64 * structure, each filter input must come from its own input
65 * stream. So the channelizer must be provided with <EM>M</EM> streams
66 * where the input stream has been deinterleaved. This is most easily
67 * done using the gr_stream_to_streams block.
69 * The output is then produced as a vector, where index <EM>i</EM> in
70 * the vector is the next sample from the <EM>i</EM>th channel. This
71 * is most easily handled by sending the output to a
72 * gr_vector_to_streams block to handle the conversion and passing
73 * <EM>M</EM> streams out.
75 * The input and output formatting is done using a hier_block2 called
76 * pfb_channelizer_ccf. This can take in a single stream and outputs
77 * <EM>M</EM> streams based on the behavior described above.
79 * The filter's taps should be based on the input sampling rate.
81 * For example, using the GNU Radio's firdes utility to building
82 * filters, we build a low-pass filter with a sampling rate of
83 * <EM>fs</EM>, a 3-dB bandwidth of <EM>BW</EM> and a transition
84 * bandwidth of <EM>TB</EM>. We can also specify the out-of-band
85 * attenuation to use, <EM>ATT</EM>, and the filter window
86 * function (a Blackman-harris window in this case). The first input
87 * is the gain of the filter, which we specify here as unity.
89 * <B><EM>self._taps = gr.firdes.low_pass_2(1, fs, BW, TB,
90 * attenuation_dB=ATT, window=gr.firdes.WIN_BLACKMAN_hARRIS)</EM></B>
92 * The filter output can also be overs ampled. The over sampling rate
93 * is the ratio of the the actual output sampling rate to the normal
94 * output sampling rate. It must be rationally related to the number
95 * of channels as N/i for i in [1,N], which gives an outputsample rate
96 * of [fs/N, fs] where fs is the input sample rate and N is the number
99 * For example, for 6 channels with fs = 6000 Hz, the normal rate is
100 * 6000/6 = 1000 Hz. Allowable oversampling rates are 6/6, 6/5, 6/4,
101 * 6/3, 6/2, and 6/1 where the output sample rate of a 6/1 oversample
102 * ratio is 6000 Hz, or 6 times the normal 1000 Hz. A rate of 6/5 = 1.2,
103 * so the output rate would be 1200 Hz.
105 * The theory behind this block can be found in Chapter 6 of
106 * the following book.
108 * <B><EM>f. harris, "Multirate Signal Processing for Communication
109 * Systems," Upper Saddle River, NJ: Prentice Hall, Inc. 2004.</EM></B>
113 class gr_pfb_channelizer_ccf : public gr_block
117 * Build the polyphase filterbank decimator.
118 * \param numchans (unsigned integer) Specifies the number of channels <EM>M</EM>
119 * \param taps (vector/list of floats) The prototype filter to populate the filterbank.
120 * \param oversample_rate (float) The over sampling rate is the ratio of the the actual
121 * output sampling rate to the normal output sampling rate.
122 * It must be rationally related to the number of channels
123 * as N/i for i in [1,N], which gives an outputsample rate
124 * of [fs/N, fs] where fs is the input sample rate and N is
125 * the number of channels.
127 * For example, for 6 channels with fs = 6000 Hz, the normal
128 * rate is 6000/6 = 1000 Hz. Allowable oversampling rates
129 * are 6/6, 6/5, 6/4, 6/3, 6/2, and 6/1 where the output
130 * sample rate of a 6/1 oversample ratio is 6000 Hz, or
131 * 6 times the normal 1000 Hz.
133 friend gr_pfb_channelizer_ccf_sptr gr_make_pfb_channelizer_ccf (unsigned int numchans,
134 const std::vector<float> &taps,
135 float oversample_rate);
138 unsigned int d_numchans;
139 float d_oversample_rate;
140 std::vector<gr_fir_ccf*> d_filters;
141 std::vector< std::vector<float> > d_taps;
142 unsigned int d_taps_per_filter;
143 gri_fft_complex *d_fft;
146 int d_output_multiple;
149 * Build the polyphase filterbank decimator.
150 * \param numchans (unsigned integer) Specifies the number of channels <EM>M</EM>
151 * \param taps (vector/list of floats) The prototype filter to populate the filterbank.
152 * \param oversample_rate (float) The output over sampling rate.
154 gr_pfb_channelizer_ccf (unsigned int numchans,
155 const std::vector<float> &taps,
156 float oversample_rate);
159 ~gr_pfb_channelizer_ccf ();
162 * Resets the filterbank's filter taps with the new prototype filter
163 * \param taps (vector/list of floats) The prototype filter to populate the filterbank.
165 void set_taps (const std::vector<float> &taps);
168 * Print all of the filterbank taps to screen.
172 int general_work (int noutput_items,
173 gr_vector_int &ninput_items,
174 gr_vector_const_void_star &input_items,
175 gr_vector_void_star &output_items);