pfb_interpolator_ccf.h

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/* -*- c++ -*- */
/*
 * Copyright 2009,2012 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 */
 
 
#ifndef INCLUDED_PFB_INTERPOLATOR_CCF_H
#define INCLUDED_PFB_INTERPOLATOR_CCF_H
 
#include <gnuradio/filter/api.h>
#include <gnuradio/sync_interpolator.h>
 
namespace gr {
namespace filter {
 
/*!
 * \brief Polyphase filterbank interpolator with gr_complex input,
 * gr_complex output and float taps
 * \ingroup channelizers_blk
 *
 * \details
 * This block takes in a signal stream and performs integer up-
 * sampling (interpolation) with a polyphase filterbank. The first
 * input is the integer specifying how much to interpolate by. The
 * second input is a vector (Python list) of floating-point taps
 * of the prototype filter.
 *
 * The filter's taps should be based on the interpolation rate
 * specified. That is, the bandwidth specified is relative to the
 * bandwidth after interpolation.
 *
 * 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, ATT, and the filter window function (a
 * Blackman-harris window in this case). The first input is the
 * gain, which is also specified as the interpolation rate so that
 * the output levels are the same as the input (this creates an
 * overall increase in power).
 *
 *   <B><EM>self._taps = filter.firdes.low_pass_2(interp, interp*fs, BW, TB,
 *      attenuation_dB=ATT, window=fft.window.WIN_BLACKMAN_hARRIS)</EM></B>
 *
 * The PFB interpolator code takes the taps generated above and
 * builds a set of filters. The set contains <EM>interp</EM>
 * filters and each filter contains
 * ceil(taps.size()/interp) 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.
 *
 * The theory behind this block can be found in Chapter 7.1 of the
 * following book:
 *
 *    <B><EM>f. harris, "Multirate Signal Processing for Communication
 *       Systems</EM>," Upper Saddle River, NJ: Prentice Hall,
 *       Inc. 2004.</EM></B>
 */
 
class FILTER_API pfb_interpolator_ccf : virtual public sync_interpolator
{
public:
    // gr::filter::pfb_interpolator_ccf::sptr
    typedef std::shared_ptr<pfb_interpolator_ccf> sptr;
 
    /*!
     * Build the polyphase filterbank interpolator.
     * \param interp  (unsigned integer) Specifies the interpolation rate to use
     * \param taps    (vector/list of floats) The prototype filter to populate the
     * filterbank. The taps should be generated at the interpolated sampling rate.
     */
    static sptr make(unsigned int interp, const std::vector<float>& taps);
 
    /*!
     * Resets the filterbank's filter taps with the new prototype filter
     * \param taps    (vector/list of floats) The prototype filter to populate the
     * filterbank. The taps should be generated at the interpolated sampling rate.
     */
    virtual void set_taps(const std::vector<float>& taps) = 0;
 
    /*!
     * Return a vector<vector<>> of the filterbank taps
     */
    virtual std::vector<std::vector<float>> taps() const = 0;
 
    /*!
     * Print all of the filterbank taps to screen.
     */
    virtual void print_taps() = 0;
};
 
} /* namespace filter */
} /* namespace gr */
 
#endif /* INCLUDED_FILTER_PFB_INTERPOLATOR_CCF_H */