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Diffstat (limited to 'gnuradio-core/src/lib/general/gr_firdes.h')
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diff --git a/gnuradio-core/src/lib/general/gr_firdes.h b/gnuradio-core/src/lib/general/gr_firdes.h new file mode 100644 index 0000000000..734f8ee9fe --- /dev/null +++ b/gnuradio-core/src/lib/general/gr_firdes.h @@ -0,0 +1,225 @@ +/* -*- 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 2, 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., 59 Temple Place - Suite 330, + * Boston, MA 02111-1307, USA. + */ + +#ifndef _GR_FIRDES_H_ +#define _GR_FIRDES_H_ + +#include <vector> +#include <cmath> +#include <gr_complex.h> + +/*! + * \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<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 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<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 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<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 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<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 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<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 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<float> + hilbert (unsigned int ntaps, + 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<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 + * + * \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<float> + gaussian (double gain, + double spb, + double bt, // Bandwidth to bitrate ratio + int ntaps); + + // window functions ... + static std::vector<float> 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 |