ghaddab
56c3197b09
git-svn-id: http://svn.eurecom.fr/openair4G/trunk@5713 818b1a75-f10b-46b9-bf7c-635c3b92a50f
89 lines
2.8 KiB
C
89 lines
2.8 KiB
C
/*******************************************************************************
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OpenAirInterface
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Copyright(c) 1999 - 2014 Eurecom
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OpenAirInterface is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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OpenAirInterface is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with OpenAirInterface.The full GNU General Public License is
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included in this distribution in the file called "COPYING". If not,
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see <http://www.gnu.org/licenses/>.
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Contact Information
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OpenAirInterface Admin: openair_admin@eurecom.fr
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OpenAirInterface Tech : openair_tech@eurecom.fr
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OpenAirInterface Dev : openair4g-devel@eurecom.fr
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Address : Eurecom, Campus SophiaTech, 450 Route des Chappes, CS 50193 - 06904 Biot Sophia Antipolis cedex, FRANCE
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*******************************************************************************/
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#include <math.h>
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// ******* FFT function **********************************************************
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#define PI 3.14159264359
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#define SWAP(a,b) tempr=(a); (a)=(b); (b)=tempr
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void FFT(float *data, // the vector with the outputs
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// real part in even indexes
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// imaginary part in the odd indexes
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// for power conservation, the output should be normalized by 1/sqrt(nn)
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unsigned long nn, // number of complex samples
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int isign) // isign = 1 -> FFT, -1 -> iFFT
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{
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unsigned long n,mmax,m,j,istep,i;
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float wtemp,wr,wpr,wpi,wi,theta;
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float tempr,tempi;
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n = nn << 1;
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j = 1;
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for( i = 1 ; i < n ; i += 2){ // The bit-reversal
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if(j > i){
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SWAP(data[j-1],data[i-1]); // Exchanging the two complex number
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SWAP(data[j],data[i]);
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}
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m = n >> 1;
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while((m >= 2)&&(j > m)){
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j -= m;
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m >>= 1;
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}
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j += m;
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}
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mmax = 2;
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while(n > mmax){
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istep = mmax << 1;
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theta = isign*(-2*PI/mmax);
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wtemp = sin(0.5 * theta);
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wpr = -2.0 * wtemp * wtemp;
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wpi = sin(theta);
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wr = 1.0;
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wi = 0.0;
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for (m = 1; m < mmax; m += 2){
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for (i = m; i <= n; i += istep){
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j = i + mmax;
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tempr = wr*data[j-1] - wi*data[j];
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tempi = wr*data[j] + wi*data[j-1];
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data[j-1] = data[i-1] - tempr;
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data[j] = data[i] - tempi;
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data[i-1] += tempr;
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data[i] += tempi;
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}
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wr = (wtemp=wr)*wpr - wi*wpi + wr;
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wi = wi*wpr + wtemp*wpi + wi;
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}
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mmax = istep;
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}
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}
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