fir.c

/*  fir.c

This file is part of a program that implements a Software-Defined Radio.

Copyright (C) 2013, 2016 Warren Pratt, NR0V

This program 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
of the License, or (at your option) any later version.

This program 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 this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.

The author can be reached by email at  

warren@wpratt.com

*/

#define _CRT_SECURE_NO_WARNINGS
#include "comm.h"

double* fftcv_mults (int NM, double* c_impulse)
{
	double* mults        = (double *) malloc0 (NM * sizeof (complex));
	double* cfft_impulse = (double *) malloc0 (NM * sizeof (complex));
	fftw_plan ptmp = fftw_plan_dft_1d(NM, (fftw_complex *) cfft_impulse,
			(fftw_complex *) mults, FFTW_FORWARD, FFTW_PATIENT);
	memset (cfft_impulse, 0, NM * sizeof (complex));
	// store complex coefs right-justified in the buffer
	memcpy (&(cfft_impulse[NM - 2]), c_impulse, (NM / 2 + 1) * sizeof(complex));
	fftw_execute (ptmp);
	fftw_destroy_plan (ptmp);
	_aligned_free (cfft_impulse);
	return mults;
}

double* get_fsamp_window(int N, int wintype)
{
	int i;
	double arg0, arg1;
	double* window = (double *) malloc0 (N * sizeof(double));
	switch (wintype)
	{
	case 0:
		arg0 = 2.0 * PI / ((double)N - 1.0);
		for (i = 0; i < N; i++)
		{
			arg1 = cos(arg0 * (double)i);
			window[i]  =   +0.21747
				+ arg1 *  (-0.45325
				+ arg1 *  (+0.28256
				+ arg1 *  (-0.04672)));
		}
		break;
	case 1:
		arg0 = 2.0 * PI / ((double)N - 1.0);
		for (i = 0; i < N; ++i)
		{
			arg1 = cos(arg0 * (double)i);
			window[i]  =   +6.3964424114390378e-02
				+ arg1 *  (-2.3993864599352804e-01
				+ arg1 *  (+3.5015956323820469e-01
				+ arg1 *  (-2.4774111897080783e-01
				+ arg1 *  (+8.5438256055858031e-02
				+ arg1 *  (-1.2320203369293225e-02
				+ arg1 *  (+4.3778825791773474e-04))))));
		}
		break;
	default:
		for (i = 0; i < N; i++)
			window[i] = 1.0;
	}
	return window;
}

double* fir_fsamp_odd (int N, double* A, int rtype, double scale, int wintype)
{
	int i, j;
	int mid = (N - 1) / 2;
	double mag, phs;
	double* window;
	double *fcoef     = (double *) malloc0 (N * sizeof (complex));
	double *c_impulse = (double *) malloc0 (N * sizeof (complex));
	fftw_plan ptmp = fftw_plan_dft_1d(N, (fftw_complex *)fcoef, (fftw_complex *)c_impulse, FFTW_BACKWARD, FFTW_PATIENT);
	double local_scale = 1.0 / (double)N;
	for (i = 0; i <= mid; i++)
	{
		mag = A[i] * local_scale;
		phs = - (double)mid * TWOPI * (double)i / (double)N;
		fcoef[2 * i + 0] = mag * cos (phs);
		fcoef[2 * i + 1] = mag * sin (phs);
	}
	for (i = mid + 1, j = 0; i < N; i++, j++)
	{
		fcoef[2 * i + 0] = + fcoef[2 * (mid - j) + 0];
		fcoef[2 * i + 1] = - fcoef[2 * (mid - j) + 1];
	}
	fftw_execute (ptmp);
	fftw_destroy_plan (ptmp);
	_aligned_free (fcoef);
	window = get_fsamp_window(N, wintype);
	switch (rtype)
	{
	case 0:
		for (i = 0; i < N; i++)
			c_impulse[i] = scale * c_impulse[2 * i] * window[i];
		break;
	case 1:
		for (i = 0; i < N; i++)
		{
			c_impulse[2 * i + 0] *= scale * window[i];
			c_impulse[2 * i + 1] = 0.0;
		}
		break;
	}
	_aligned_free (window);
	return c_impulse;
}

double* fir_fsamp (int N, double* A, int rtype, double scale, int wintype)
{
	int n, i, j, k;
	double sum;
	double* window;
	double *c_impulse = (double *) malloc0 (N * sizeof (complex));

	if (N & 1)
	{
		int M = (N - 1) / 2;
		for (n = 0; n < M + 1; n++)
		{
			sum = 0.0;
			for (k = 1; k < M + 1; k++)
				sum += 2.0 * A[k] * cos(TWOPI * (n - M) * k / N);
			c_impulse[2 * n + 0] = (1.0 / N) * (A[0] + sum);
			c_impulse[2 * n + 1] = 0.0;
		}
		for (n = M + 1, j = 1; n < N; n++, j++)
		{
			c_impulse[2 * n + 0] = c_impulse[2 * (M - j) + 0];
			c_impulse[2 * n + 1] = 0.0;
		}
	}
	else
	{
		double M = (double)(N - 1) / 2.0;
		for (n = 0; n < N / 2; n++)
		{
			sum = 0.0;
			for (k = 1; k < N / 2; k++)
				sum += 2.0 * A[k] * cos(TWOPI * (n - M) * k / N);
			c_impulse[2 * n + 0] = (1.0 / N) * (A[0] + sum);
			c_impulse[2 * n + 1] = 0.0;
		}
		for (n = N / 2, j = 1; n < N; n++, j++)
		{
			c_impulse[2 * n + 0] = c_impulse[2 * (N / 2 - j) + 0];
			c_impulse[2 * n + 1] = 0.0;
		}
	}
	window = get_fsamp_window (N, wintype);
	switch (rtype)
	{
	case 0:
		for (i = 0; i < N; i++)
			c_impulse[i] = scale * c_impulse[2 * i] * window[i];
		break;
	case 1:
		for (i = 0; i < N; i++)
			{
				c_impulse[2 * i + 0] *= scale * window[i];
				c_impulse[2 * i + 1] = 0.0;
			}
		break;
	}
	_aligned_free (window);
	return c_impulse;
}

double* fir_bandpass (int N, double f_low, double f_high, double samplerate, int wintype, int rtype, double scale)
{
	double *c_impulse = (double *) malloc0 (N * sizeof (complex));
	double ft = (f_high - f_low) / (2.0 * samplerate);
	double ft_rad = TWOPI * ft;
	double w_osc = PI * (f_high + f_low) / samplerate;
	int i, j;
	double m = 0.5 * (double)(N - 1);
	double delta = PI / m;
	double cosphi;
	double posi, posj;
	double sinc, window, coef;

	if (N & 1)
	{
		switch (rtype)
		{
		case 0:
			c_impulse[N >> 1] = scale * 2.0 * ft;
			break;
		case 1:
			c_impulse[N - 1] = scale * 2.0 * ft;
			c_impulse[  N  ] = 0.0;
			break;
		}
	}
	for (i = (N + 1) / 2, j = N / 2 - 1; i < N; i++, j--)
	{
		posi = (double)i - m;
		posj = (double)j - m;
		sinc = sin (ft_rad * posi) / (PI * posi);
		switch (wintype)
		{
		case 0:	// Blackman-Harris 4-term
			cosphi = cos (delta * i);
			window  =             + 0.21747
					+ cosphi *  ( - 0.45325
					+ cosphi *  ( + 0.28256
					+ cosphi *  ( - 0.04672 )));
			break;
		case 1:	// Blackman-Harris 7-term
			cosphi = cos (delta * i);
			window	=			  + 6.3964424114390378e-02
					+ cosphi *  ( - 2.3993864599352804e-01
					+ cosphi *  ( + 3.5015956323820469e-01
					+ cosphi *	( - 2.4774111897080783e-01
					+ cosphi *  ( + 8.5438256055858031e-02
					+ cosphi *	( - 1.2320203369293225e-02
					+ cosphi *	( + 4.3778825791773474e-04 ))))));
			break;
		}
		coef = scale * sinc * window;
		switch (rtype)
		{
		case 0:
			c_impulse[i] = + coef * cos (posi * w_osc);
			c_impulse[j] = + coef * cos (posj * w_osc);
			break;
		case 1:
			c_impulse[2 * i + 0] = + coef * cos (posi * w_osc);
			c_impulse[2 * i + 1] = - coef * sin (posi * w_osc);
			c_impulse[2 * j + 0] = + coef * cos (posj * w_osc);
			c_impulse[2 * j + 1] = - coef * sin (posj * w_osc);
			break;
		}
	}
	return c_impulse;
}

double *fir_read (int N, const char *filename, int rtype, double scale)
	// N = number of real or complex coefficients (see rtype)
	// *filename = filename
	// rtype = 0:  real coefficients
	// rtype = 1:  complex coefficients
	// scale = a scale factor that will be applied to the returned coefficients;
	//		if this is not needed, set it to 1.0
	// NOTE:  The number of values in the file must NOT exceed those implied by N and rtype
{
	FILE *file;
	int i;
	double I, Q;
	double *c_impulse = (double *) malloc0 (N * sizeof (complex));
	file = fopen (filename, "r");
	for (i = 0; i < N; i++)
	{
		// read in the complex impulse response
		// NOTE:  IF the freq response is symmetrical about 0, the imag coeffs will all be zero.
		switch (rtype)
		{
		case 0:
			fscanf (file, "%le", &I);
			c_impulse[i] = + scale * I;
			break;
		case 1:
			fscanf (file, "%le", &I);
			fscanf (file, "%le", &Q);
			c_impulse[2 * i + 0] = + scale * I;
			c_impulse[2 * i + 1] = - scale * Q;
			break;
		}
	}
	fclose (file);
	return c_impulse;
}

void analytic (int N, double* in, double* out)
{
	int i;
	double inv_N = 1.0 / (double)N;
	double two_inv_N = 2.0 * inv_N;
	double* x = (double *) malloc0 (N * sizeof (complex));
	fftw_plan pfor = fftw_plan_dft_1d (N, (fftw_complex *) in,
			(fftw_complex *) x, FFTW_FORWARD, FFTW_PATIENT);
	fftw_plan prev = fftw_plan_dft_1d (N, (fftw_complex *) x,
			(fftw_complex *) out, FFTW_BACKWARD, FFTW_PATIENT);
	fftw_execute (pfor);
	x[0] *= inv_N;
	x[1] *= inv_N;
	for (i = 1; i < N / 2; i++)
	{
		x[2 * i + 0] *= two_inv_N;
		x[2 * i + 1] *= two_inv_N;
	}
	x[N + 0] *= inv_N;
	x[N + 1] *= inv_N;
	memset (&x[N + 2], 0, (N - 2) * sizeof (double));
	fftw_execute (prev);
	fftw_destroy_plan (prev);
	fftw_destroy_plan (pfor);
	_aligned_free (x);
}

void mp_imp (int N, double* fir, double* mpfir, int pfactor, int polarity)
{
	int i;
	int size = N * pfactor;
	double inv_PN = 1.0 / (double)size;
	double* firpad  = (double *) malloc0 (size * sizeof (complex));
	double* firfreq = (double *) malloc0 (size * sizeof (complex));
	double* mag     = (double *) malloc0 (size * sizeof (double));
	double* ana     = (double *) malloc0 (size * sizeof (complex));
	double* impulse = (double *) malloc0 (size * sizeof (complex));
	double* newfreq = (double *) malloc0 (size * sizeof (complex));
	memcpy (firpad, fir, N * sizeof (complex));
	fftw_plan pfor = fftw_plan_dft_1d (size, (fftw_complex *) firpad,
			(fftw_complex *) firfreq, FFTW_FORWARD, FFTW_PATIENT);
	fftw_plan prev = fftw_plan_dft_1d (size, (fftw_complex *) newfreq,
			(fftw_complex *) impulse, FFTW_BACKWARD, FFTW_PATIENT);
	// print_impulse("orig_imp.txt", N, fir, 1, 0);
	fftw_execute (pfor);
	for (i = 0; i < size; i++)
	{
		mag[i] = sqrt (firfreq[2 * i + 0] * firfreq[2 * i + 0] + firfreq[2 * i + 1] * firfreq[2 * i + 1]) * inv_PN;
		if (mag[i] > 0.0)
			ana[2 * i + 0] = log (mag[i]);
		else
			ana[2 * i + 0] = log (1.0e-300);
	}
	analytic (size, ana, ana);
	for (i = 0; i < size; i++)
	{
		newfreq[2 * i + 0] = + mag[i] * cos (ana[2 * i + 1]);
		if (polarity)
			newfreq[2 * i + 1] = + mag[i] * sin (ana[2 * i + 1]);
		else
			newfreq[2 * i + 1] = - mag[i] * sin (ana[2 * i + 1]);
	}
	fftw_execute (prev);
	if (polarity)
		memcpy (mpfir, &impulse[2 * (pfactor - 1) * N], N * sizeof (complex));
	else
		memcpy (mpfir, impulse, N * sizeof (complex));
	// print_impulse("min_imp.txt", N, mpfir, 1, 0);
	fftw_destroy_plan (prev);
	fftw_destroy_plan (pfor);
	_aligned_free (newfreq);
	_aligned_free (impulse);
	_aligned_free (ana);
	_aligned_free (mag);
	_aligned_free (firfreq);
	_aligned_free (firpad);
}