firdes.h

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/* -*- c++ -*- */
/*
 * Copyright 2002,2008,2012 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * GNU Radio is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 3, or (at your option)
 * any later version.
 *
 * GNU Radio is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with GNU Radio; see the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifndef _FILTER_FIRDES_H_
#define _FILTER_FIRDES_H_

#include <gnuradio/fft/window.h>
#include <gnuradio/filter/api.h>
#include <gnuradio/gr_complex.h>
#include <cmath>
#include <vector>

namespace gr {
namespace filter {

/*!
 * \brief Finite Impulse Response (FIR) filter design functions.
 * \ingroup filter_design
 */

class FILTER_API firdes
{
public:
    // WARNING: deprecated, now located in gr::fft::window.
    // We will be removing this in 3.8.
    enum win_type {
        WIN_NONE = -1,       //!< don't use a window
        WIN_HAMMING = 0,     //!< Hamming window; max attenuation 53 dB
        WIN_HANN = 1,        //!< Hann window; max attenuation 44 dB
        WIN_BLACKMAN = 2,    //!< Blackman window; max attenuation 74 dB
        WIN_RECTANGULAR = 3, //!< Basic rectangular window
        WIN_KAISER = 4, //!< Kaiser window; max attenuation a function of beta, google it
        WIN_BLACKMAN_hARRIS = 5, //!< Blackman-harris window
        WIN_BLACKMAN_HARRIS =
            5,            //!< alias to WIN_BLACKMAN_hARRIS for capitalization consistency
        WIN_BARTLETT = 6, //!< Barlett (triangular) window
        WIN_FLATTOP = 7,  //!< flat top window; useful in FFTs
    };

    static std::vector<float> window(win_type type, int ntaps, double beta);

    // ... class methods ...

    /*!
     * \brief Use "window method" to design a low-pass FIR filter.  The
     * normalized width of the transition band is what sets the number of
     * taps required.  Narrow --> more taps.  Window type determines maximum
     * attenuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param cutoff_freq               center of transition band (Hz)
     * \param transition_width  width of transition band (Hz)
     * \param window              one of firdes::win_type
     * \param beta                parameter for Kaiser window
     */
    static std::vector<float>
    low_pass(double gain,
             double sampling_freq,
             double cutoff_freq,      // Hz center of transition band
             double transition_width, // Hz width of transition band
             win_type window = WIN_HAMMING,
             double beta = 6.76); // used only with Kaiser

    /*!
     * \brief Use "window method" to design a low-pass FIR filter.  The
     * normalized width of the transition band and the required stop band
     * attenuation is what sets the number of taps required.  Narrow --> more
     * taps More attenuation --> more taps. The window type determines
     * maximum attentuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param cutoff_freq         beginning of transition band (Hz)
     * \param transition_width    width of transition band (Hz)
     * \param attenuation_dB      required stopband attenuation
     * \param window              one of firdes::win_type
     * \param beta                      parameter for Kaiser window
     */
    static std::vector<float>
    low_pass_2(double gain,
               double sampling_freq,
               double cutoff_freq,      // Hz beginning transition band
               double transition_width, // Hz width of transition band
               double attenuation_dB,   // out of band attenuation dB
               win_type window = WIN_HAMMING,
               double beta = 6.76); // used only with Kaiser

    /*!
     * \brief Use "window method" to design a high-pass FIR filter.  The
     * normalized width of the transition band is what sets the number of
     * taps required.  Narrow --> more taps. The window determines maximum
     * attenuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param cutoff_freq         center of transition band (Hz)
     * \param transition_width    width of transition band (Hz)
     * \param window              one of firdes::win_type
     * \param beta                parameter for Kaiser window
     */
    static std::vector<float>
    high_pass(double gain,
              double sampling_freq,
              double cutoff_freq,      // Hz center of transition band
              double transition_width, // Hz width of transition band
              win_type window = WIN_HAMMING,
              double beta = 6.76); // used only with Kaiser

    /*!
     * \brief Use "window method" to design a high-pass FIR filter. The
     * normalized width of the transition band and the required stop band
     * attenuation is what sets the number of taps required.  Narrow --> more
     * taps More attenuation --> more taps. The window determines maximum
     * attenuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param cutoff_freq         center of transition band (Hz)
     * \param transition_width    width of transition band (Hz).
     * \param attenuation_dB      out of band attenuation
     * \param window              one of firdes::win_type
     * \param beta                parameter for Kaiser window
     */
    static std::vector<float>
    high_pass_2(double gain,
                double sampling_freq,
                double cutoff_freq,      // Hz center of transition band
                double transition_width, // Hz width of transition band
                double attenuation_dB,   // out of band attenuation dB
                win_type window = WIN_HAMMING,
                double beta = 6.76); // used only with Kaiser

    /*!
     * \brief Use "window method" to design a band-pass FIR filter. The
     * normalized width of the transition band is what sets the number of
     * taps required.  Narrow --> more taps. The window determines maximum
     * attenuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param low_cutoff_freq     center of transition band (Hz)
     * \param high_cutoff_freq    center of transition band (Hz)
     * \param transition_width    width of transition band (Hz).
     * \param window              one of firdes::win_type
     * \param beta                parameter for Kaiser window
     */
    static std::vector<float>
    band_pass(double gain,
              double sampling_freq,
              double low_cutoff_freq,  // Hz center of transition band
              double high_cutoff_freq, // Hz center of transition band
              double transition_width, // Hz width of transition band
              win_type window = WIN_HAMMING,
              double beta = 6.76); // used only with Kaiser

    /*!
     * \brief Use "window method" to design a band-pass FIR filter.  The
     * normalized width of the transition band and the required stop band
     * attenuation is what sets the number of taps required.  Narrow --> more
     * taps.  More attenuation --> more taps.  Window type determines maximum
     * attenuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param low_cutoff_freq     center of transition band (Hz)
     * \param high_cutoff_freq    center of transition band (Hz)
     * \param transition_width    width of transition band (Hz).
     * \param attenuation_dB      out of band attenuation
     * \param window              one of firdes::win_type
     * \param beta                parameter for Kaiser window
     */
    static std::vector<float>
    band_pass_2(double gain,
                double sampling_freq,
                double low_cutoff_freq,  // Hz beginning transition band
                double high_cutoff_freq, // Hz beginning transition band
                double transition_width, // Hz width of transition band
                double attenuation_dB,   // out of band attenuation dB
                win_type window = WIN_HAMMING,
                double beta = 6.76); // used only with Kaiser

    /*!
     * \brief Use the "window method" to design a complex band-pass FIR
     * filter.  The normalized width of the transition band is what sets the
     * number of taps required.  Narrow --> more taps. The window type
     * determines maximum attenuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param low_cutoff_freq     center of transition band (Hz)
     * \param high_cutoff_freq    center of transition band (Hz)
     * \param transition_width    width of transition band (Hz)
     * \param window              one of firdes::win_type
     * \param beta                parameter for Kaiser window
     */
    static std::vector<gr_complex>
    complex_band_pass(double gain,
                      double sampling_freq,
                      double low_cutoff_freq,  // Hz center of transition band
                      double high_cutoff_freq, // Hz center of transition band
                      double transition_width, // Hz width of transition band
                      win_type window = WIN_HAMMING,
                      double beta = 6.76); // used only with Kaiser

    /*!
     * \brief Use "window method" to design a complex band-pass FIR filter.
     * The normalized width of the transition band and the required stop band
     * attenuation is what sets the number of taps required.  Narrow --> more
     * taps More attenuation --> more taps. Window type determines maximum
     * attenuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param low_cutoff_freq     center of transition band (Hz)
     * \param high_cutoff_freq    center of transition band (Hz)
     * \param transition_width    width of transition band (Hz)
     * \param attenuation_dB      out of band attenuation
     * \param window              one of firdes::win_type
     * \param beta                parameter for Kaiser window
     */
    static std::vector<gr_complex>
    complex_band_pass_2(double gain,
                        double sampling_freq,
                        double low_cutoff_freq,  // Hz beginning transition band
                        double high_cutoff_freq, // Hz beginning transition band
                        double transition_width, // Hz width of transition band
                        double attenuation_dB,   // out of band attenuation dB
                        win_type window = WIN_HAMMING,
                        double beta = 6.76); // used only with Kaiser

    /*!
     * \brief Use "window method" to design a band-reject FIR filter.  The
     * normalized width of the transition band is what sets the number of
     * taps required.  Narrow --> more taps. Window type determines maximum
     * attenuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param low_cutoff_freq     center of transition band (Hz)
     * \param high_cutoff_freq    center of transition band (Hz)
     * \param transition_width    width of transition band (Hz)
     * \param window              one of firdes::win_type
     * \param beta                parameter for Kaiser window
     */
    static std::vector<float>
    band_reject(double gain,
                double sampling_freq,
                double low_cutoff_freq,  // Hz center of transition band
                double high_cutoff_freq, // Hz center of transition band
                double transition_width, // Hz width of transition band
                win_type window = WIN_HAMMING,
                double beta = 6.76); // used only with Kaiser

    /*!
     * \brief Use "window method" to design a band-reject FIR filter.  The
     * normalized width of the transition band and the required stop band
     * attenuation is what sets the number of taps required.  Narrow --> more
     * taps More attenuation --> more taps.  Window type determines maximum
     * attenuation and passband ripple.
     *
     * \param gain                overall gain of filter (typically 1.0)
     * \param sampling_freq       sampling freq (Hz)
     * \param low_cutoff_freq     center of transition band (Hz)
     * \param high_cutoff_freq    center of transition band (Hz)
     * \param transition_width    width of transition band (Hz).
     * \param attenuation_dB      out of band attenuation
     * \param window              one of firdes::win_type
     * \param beta                parameter for Kaiser window
     */
    static std::vector<float>
    band_reject_2(double gain,
                  double sampling_freq,
                  double low_cutoff_freq,  // Hz beginning transition band
                  double high_cutoff_freq, // Hz beginning transition band
                  double transition_width, // Hz width of transition band
                  double attenuation_dB,   // out of band attenuation dB
                  win_type window = WIN_HAMMING,
                  double beta = 6.76); // used only with Kaiser

    /*!\brief design a Hilbert Transform Filter
     *
     * \param ntaps           number of taps, must be odd
     * \param windowtype      one kind of firdes::win_type
     * \param beta            parameter for Kaiser window
     */
    static std::vector<float> hilbert(unsigned int ntaps = 19,
                                      win_type windowtype = WIN_RECTANGULAR,
                                      double beta = 6.76);

    /*!
     * \brief design a Root Cosine FIR Filter (do we need a window?)
     *
     * \param gain            overall gain of filter (typically 1.0)
     * \param sampling_freq   sampling freq (Hz)
     * \param symbol_rate     symbol rate, must be a factor of sample rate
     * \param alpha           excess bandwidth factor
     * \param ntaps           number of taps
     */
    static std::vector<float>
    root_raised_cosine(double gain,
                       double sampling_freq,
                       double symbol_rate, // Symbol rate, NOT bitrate (unless BPSK)
                       double alpha,       // Excess Bandwidth Factor
                       int ntaps);

    /*!
     * \brief design a Gaussian filter
     *
     * \param gain    overall gain of filter (typically 1.0)
     * \param spb     symbol rate, must be a factor of sample rate
     * \param bt      bandwidth to bitrate ratio
     * \param ntaps   number of taps
     */
    static std::vector<float> gaussian(double gain,
                                       double spb,
                                       double bt, // Bandwidth to bitrate ratio
                                       int ntaps);

private:
    static double bessi0(double x);
    static void sanity_check_1f(double sampling_freq, double f1, double transition_width);
    static void
    sanity_check_2f(double sampling_freq, double f1, double f2, double transition_width);
    static void sanity_check_2f_c(double sampling_freq,
                                  double f1,
                                  double f2,
                                  double transition_width);

    static int compute_ntaps(double sampling_freq,
                             double transition_width,
                             win_type window_type,
                             double beta);

    static int compute_ntaps_windes(double sampling_freq,
                                    double transition_width,
                                    double attenuation_dB);
};

} /* namespace filter */
} /* namespace gr */

#endif /* _FILTER_FIRDES_H_ */