/* -*- c++ -*- */ /* * Copyright 2002 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 _GR_FIRDES_H_ #define _GR_FIRDES_H_ #include #include #include /*! * \brief Finite Impulse Response (FIR) filter design functions. */ class gr_firdes { public: enum win_type { WIN_HAMMING = 0, // max attenuation 53 dB WIN_HANN = 1, // max attenuation 44 dB WIN_BLACKMAN = 2, // max attenuation 74 dB WIN_RECTANGULAR = 3, WIN_KAISER = 4 // max attenuation a function of beta, google it }; // ... class methods ... /*! * \brief use "window method" to design a low-pass FIR filter * * \p gain: overall gain of filter (typically 1.0) * \p sampling_freq: sampling freq (Hz) * \p cutoff_freq: center of transition band (Hz) * \p transition_width: width of transition band (Hz). * The normalized width of the transition * band is what sets the number of taps * required. Narrow --> more taps * \p window_type: What kind of window to use. Determines * maximum attenuation and passband ripple. * \p beta: parameter for Kaiser window */ static std::vector 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 high-pass FIR filter * * \p gain: overall gain of filter (typically 1.0) * \p sampling_freq: sampling freq (Hz) * \p cutoff_freq: center of transition band (Hz) * \p transition_width: width of transition band (Hz). * The normalized width of the transition * band is what sets the number of taps * required. Narrow --> more taps * \p window_type: What kind of window to use. Determines * maximum attenuation and passband ripple. * \p beta: parameter for Kaiser window */ static std::vector 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 band-pass FIR filter * * \p gain: overall gain of filter (typically 1.0) * \p sampling_freq: sampling freq (Hz) * \p low_cutoff_freq: center of transition band (Hz) * \p high_cutoff_freq: center of transition band (Hz) * \p transition_width: width of transition band (Hz). * The normalized width of the transition * band is what sets the number of taps * required. Narrow --> more taps * \p window_type: What kind of window to use. Determines * maximum attenuation and passband ripple. * \p beta: parameter for Kaiser window */ static std::vector 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 * * \p gain: overall gain of filter (typically 1.0) * \p sampling_freq: sampling freq (Hz) * \p low_cutoff_freq: center of transition band (Hz) * \p high_cutoff_freq: center of transition band (Hz) * \p transition_width: width of transition band (Hz). * The normalized width of the transition * band is what sets the number of taps * required. Narrow --> more taps * \p window_type: What kind of window to use. Determines * maximum attenuation and passband ripple. * \p beta: parameter for Kaiser window */ static std::vector 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 band-reject FIR filter * * \p gain: overall gain of filter (typically 1.0) * \p sampling_freq: sampling freq (Hz) * \p low_cutoff_freq: center of transition band (Hz) * \p high_cutoff_freq: center of transition band (Hz) * \p transition_width: width of transition band (Hz). * The normalized width of the transition * band is what sets the number of taps * required. Narrow --> more taps * \p window_type: What kind of window to use. Determines * maximum attenuation and passband ripple. * \p beta: parameter for Kaiser window */ static std::vector 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 design a Hilbert Transform Filter * * \p ntaps: Number of taps, must be odd * \p window_type: What kind of window to use * \p beta: Only used for Kaiser */ static std::vector 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?) * * \p gain: overall gain of filter (typically 1.0) * \p sampling_freq: sampling freq (Hz) * \p symbol rate: symbol rate, must be a factor of sample rate * \p alpha: excess bandwidth factor * \p ntaps: number of taps */ static std::vector 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 * * \p gain: overall gain of filter (typically 1.0) * \p symbols per bit: symbol rate, must be a factor of sample rate * \p ntaps: number of taps */ static std::vector gaussian (double gain, double spb, double bt, // Bandwidth to bitrate ratio int ntaps); // window functions ... static std::vector window (win_type type, int ntaps, double beta); 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); }; #endif