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/* -*- 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 <vector>
#include <cmath>
#include <gr_complex.h>
/*!
* \brief Finite Impulse Response (FIR) filter design functions.
* \ingroup filter_design
*/
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 = 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<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
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