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pfb_channelizer_ccf.h
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/* -*- c++ -*- */
/*
* Copyright 2009,2010,2012 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#ifndef INCLUDED_FILTER_PFB_CHANNELIZER_CCF_H
#define INCLUDED_FILTER_PFB_CHANNELIZER_CCF_H
#include <gnuradio/block.h>
#include <gnuradio/filter/api.h>
namespace gr {
namespace filter {
/*!
* \brief Polyphase filterbank channelizer with
* gr_complex input, gr_complex output and float taps
* \ingroup channelizers_blk
*
* \details
* This block takes in complex inputs and channelizes it to <EM>M</EM>
* channels of equal bandwidth. Each of the resulting channels is
* decimated to the new rate that is the input sampling rate
* <EM>fs</EM> divided by the number of channels, <EM>M</EM>.
*
* The PFB channelizer code takes the taps generated above and builds
* a set of filters. The set contains <EM>M</EM>filters
* and each filter contains ceil(taps.size()/decim) taps.
* Each tap from the filter prototype is sequentially inserted into
* the next filter. When all of the input taps are used, the remaining
* filters in the filterbank are filled out with 0's to make sure each
* filter has the same number of taps.
*
* Each filter operates using the gr::blocks::fir_filter_XXX
* class of GNU Radio, which takes the input stream at <EM>i</EM>
* and performs the inner product calculation to <EM>i+(n-1)</EM>
* where <EM>n</EM> is the number of filter taps. To efficiently
* handle this in the GNU Radio structure, each filter input must
* come from its own input stream. So the channelizer must be
* provided with <EM>M</EM> streams where the input stream has
* been deinterleaved. This is most easily done using the
* gr::blocks::stream_to_streams block.
*
* The output is then produced as a vector, where index <EM>i</EM>
* in the vector is the next sample from the <EM>i</EM>th
* channel. This is most easily handled by sending the output to a
* gr::blocks::vector_to_streams block to handle the conversion
* and passing <EM>M</EM> streams out.
*
* The input and output formatting is done using a hier_block2 called
* pfb_channelizer_ccf. This can take in a single stream and outputs
* <EM>M</EM> streams based on the behavior described above.
*
* The filter's taps should be based on the input sampling rate.
*
* For example, using the GNU Radio's firdes utility to building
* filters, we build a low-pass filter with a sampling rate of
* <EM>fs</EM>, a 3-dB bandwidth of <EM>BW</EM> and a transition
* bandwidth of <EM>TB</EM>. We can also specify the out-of-band
* attenuation to use, <EM>ATT</EM>, and the filter window
* function (a Blackman-harris window in this case). The first input
* is the gain of the filter, which we specify here as unity.
*
* <B><EM>self._taps = filter.firdes.low_pass_2(1, fs, BW, TB,
* attenuation_dB=ATT, window=fft.window.WIN_BLACKMAN_hARRIS)</EM></B>
*
* The filter output can also be oversampled. The oversampling rate
* is the ratio of the the actual output sampling rate to the normal
* output sampling rate. It must be rationally related to the number
* of channels as N/i for i in [1,N], which gives an outputsample rate
* of [fs/N, fs] where fs is the input sample rate and N is the number
* of channels.
*
* For example, for 6 channels with fs = 6000 Hz, the normal rate is
* 6000/6 = 1000 Hz. Allowable oversampling rates are 6/6, 6/5, 6/4,
* 6/3, 6/2, and 6/1 where the output sample rate of a 6/1 oversample
* ratio is 6000 Hz, or 6 times the normal 1000 Hz. A rate of 6/5 = 1.2,
* so the output rate would be 1200 Hz.
*
* The theory behind this block can be found in Chapter 6 of
* the following book:
*
* <B><EM>f. harris, "Multirate Signal Processing for Communication
* Systems," Upper Saddle River, NJ: Prentice Hall, Inc. 2004.</EM></B>
*
* When dealing with oversampling, the above book is still a good
* reference along with this paper:
*
* <B><EM>E. Venosa, X. Chen, and fred harris, “Polyphase analysis
* filter bank down-converts unequal channel bandwidths with
* arbitrary center frequencies - design I,” in SDR’10-WinnComm,
* 2010.</EM></B>
*/
class FILTER_API pfb_channelizer_ccf : virtual public block
{
public:
// gr::filter::pfb_channelizer_ccf::sptr
typedef std::shared_ptr<pfb_channelizer_ccf> sptr;
/*!
* Build the polyphase filterbank decimator.
* \param numchans (unsigned integer) Specifies the number of
* channels <EM>M</EM>
* \param taps (vector/list of floats) The prototype filter to
* populate the filterbank.
* \param oversample_rate (float) The oversampling rate is the
* ratio of the the actual output
* sampling rate to the normal
* output sampling rate. It must
* be rationally related to the
* number of channels as N/i for
* i in [1,N], which gives an
* outputsample rate of [fs/N,
* fs] where fs is the input
* sample rate and N is the
* number of channels.
*
* For example, for 6 channels
* with fs = 6000 Hz, the normal
* rate is 6000/6 = 1000
* Hz. Allowable oversampling
* rates are 6/6, 6/5, 6/4, 6/3,
* 6/2, and 6/1 where the output
* sample rate of a 6/1
* oversample ratio is 6000 Hz,
* or 6 times the normal 1000 Hz.
*/
static sptr
make(unsigned int numchans, const std::vector<float>& taps, float oversample_rate);
/*!
* Resets the filterbank's filter taps with the new prototype filter
* \param taps (vector/list of floats) The prototype filter to populate the
* filterbank.
*/
virtual void set_taps(const std::vector<float>& taps) = 0;
/*!
* Print all of the filterbank taps to screen.
*/
virtual void print_taps() = 0;
/*!
* Return a vector<vector<>> of the filterbank taps
*/
virtual std::vector<std::vector<float>> taps() const = 0;
/*!
* Set the channel map. Channels are numbers as:
* <pre>
* N/2+1 | ... | N-1 | 0 | 1 | 2 | ... | N/2
* <------------------- 0 -------------------->
* freq
* </pre>
*
* So output stream 0 comes from channel 0, etc. Setting a new
* channel map allows the user to specify which channel in frequency
* he/she wants to got to which output stream.
*
* The map should have the same number of elements as the number
* of output connections from the block. The minimum value of
* the map is 0 (for the 0th channel) and the maximum number is
* N-1 where N is the number of channels.
*
* We specify M as the number of output connections made where M
* <= N, so only M out of N channels are driven to an output
* stream. The number of items in the channel map should be at
* least M long. If there are more channels specified, any value
* in the map over M-1 will be ignored. If the size of the map
* is less than M the behavior is unknown (we don't wish to
* check every entry into the work function).
*
* This means that if the channelizer is splitting the signal up
* into N channels but only M channels are specified in the map
* (where M <= N), then M output streams must be connected and
* the map and the channel numbers used must be less than
* N-1. Output channel number can be reused, too. By default,
* the map is [0...M-1] with M = N.
*/
virtual void set_channel_map(const std::vector<int>& map) = 0;
/*!
* Gets the current channel map.
*/
virtual std::vector<int> channel_map() const = 0;
};
} /* namespace filter */
} /* namespace gr */
#endif /* INCLUDED_FILTER_PFB_CHANNELIZER_CCF_H */
gr::block::block
block(void)
Definition gnuradio-runtime/include/gnuradio/block.h:806
gr::filter::pfb_channelizer_ccf
Polyphase filterbank channelizer with gr_complex input, gr_complex output and float taps.
Definition pfb_channelizer_ccf.h:101
gr::filter::pfb_channelizer_ccf::sptr
std::shared_ptr< pfb_channelizer_ccf > sptr
Definition pfb_channelizer_ccf.h:104
gr::filter::pfb_channelizer_ccf::print_taps
virtual void print_taps()=0
gr::filter::pfb_channelizer_ccf::make
static sptr make(unsigned int numchans, const std::vector< float > &taps, float oversample_rate)
gr::filter::pfb_channelizer_ccf::set_channel_map
virtual void set_channel_map(const std::vector< int > &map)=0
gr::filter::pfb_channelizer_ccf::set_taps
virtual void set_taps(const std::vector< float > &taps)=0
gr::filter::pfb_channelizer_ccf::channel_map
virtual std::vector< int > channel_map() const =0
gr::filter::pfb_channelizer_ccf::taps
virtual std::vector< std::vector< float > > taps() const =0
block.h
api.h
FILTER_API
#define FILTER_API
Definition gr-filter/include/gnuradio/filter/api.h:18
gr::filter
Definition dc_blocker_cc.h:18
gr
GNU Radio logging wrapper.
Definition basic_block.h:29