pfb_synthesizer_ccf.h

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/* -*- c++ -*- */
/*
 * Copyright 2010,2012 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 */
 
 
#ifndef INCLUDED_PFB_SYNTHESIZER_CCF_H
#define INCLUDED_PFB_SYNTHESIZER_CCF_H
 
#include <gnuradio/filter/api.h>
#include <gnuradio/sync_interpolator.h>
 
namespace gr {
namespace filter {
 
/*!
 * \brief Polyphase synthesis filterbank with
 *        gr_complex input, gr_complex output and float taps
 * \ingroup channelizers_blk
 *
 * \details
 *
 * The PFB synthesis filterbank combines multiple baseband signals
 * into a single channelized signal. Each input stream is,
 * essentially, modulated onto an output channel according the the
 * channel mapping (see set_channel_map for details).
 *
 * Setting this filterbank up means selecting the number of output
 * channels, the prototype filter, and whether to handle channels
 * at 2x the sample rate (this is generally used only for
 * reconstruction filtering).
 *
 * The number of channels sets the maximum number of channels to
 * use, but not all input streams must be connected. For M total
 * channels, we can connect inputs 0 to N where N < M-1. Because
 * of the way GNU Radio handles stream connections, we must
 * connect the channels consecutively, and so we must use the
 * set_channel_map if the desired output channels are not the same
 * as the the default mapping. This features gives us the
 * flexibility to output to any given channel. Generally, we try
 * to not use the channels at the edge of the spectrum to avoid
 * issues with filtering and roll-off of the transmitter or
 * receiver.
 *
 * When using the 2x sample rate mode, we specify the number of
 * channels that will be used. However, the actual output signal
 * will be twice this number of channels. This is mainly important
 * to know when setting the channel map. For M channels, the
 * channel mapping can specy from 0 to 2M-1 channels to output
 * onto.
 *
 * For more details about this and the concepts of reconstruction
 * filtering, see:
 *
 *    <B><EM>f. harris, "Multirate Signal Processing for Communication
 *       Systems," Upper Saddle River, NJ: Prentice Hall, Inc. 2004.</EM></B>
 *
 *    <B><EM>X. Chen, E. Venosa, and fred harris, “Polyphase analysis
 *       filter bank up-converts unequal channel bandwidths with
 *       arbitrary center frequencies - design ii,” in SDR’10-WinnComm,
 *       2010.</EM></B>
 *
 *    <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>
 *
 *    <B><EM>f. j. harris, C. Dick, X. Chen, and E. Venosa, “Wideband 160-
 *       channel polyphase filter bank cable TV channeliser,” in IET
 *       Signal Processing, 2010.</EM></B>
 */
class FILTER_API pfb_synthesizer_ccf : virtual public sync_interpolator
{
public:
    // gr::filter::pfb_synthesizer_ccf::sptr
    typedef std::shared_ptr<pfb_synthesizer_ccf> sptr;
 
    /*!
     * Build the polyphase synthesis filterbank.
     * \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 twox    (bool) use 2x oversampling or not (default is no)
     */
    static sptr
    make(unsigned int numchans, const std::vector<float>& taps, bool twox = false);
 
    /*!
     * 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 input stream 0 goes to channel 0, etc. Setting a new channel
     * map allows the user to specify where in frequency he/she wants
     * the input stream to go. This is especially useful to avoid
     * putting signals into the channels on the edge of the spectrum
     * which can either wrap around (in the case of odd number of
     * channels) and be affected by filter rolloff in the transmitter.
     *
     * The map must be at least the number of streams being sent to the
     * block. Less and the algorithm will not have enough data to
     * properly setup the buffers. Any more channels specified will be
     * ignored.
     */
    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_PFB_SYNTHESIZER_CCF_H */