120 lines
2.6 KiB
C
120 lines
2.6 KiB
C
#include "math.h"
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#include "fft.h"
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void conjugate_complex(int n,complex in[],complex out[])
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{
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int i = 0;
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for(i=0;i<n;i++)
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{
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out[i].imag = -in[i].imag;
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out[i].real = in[i].real;
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}
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}
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void c_abs(complex f[],float out[],int n)
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{
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int i = 0;
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float t;
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for(i=0;i<n;i++)
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{
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t = f[i].real * f[i].real + f[i].imag * f[i].imag;
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out[i] = iot_sqrt(t);
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}
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}
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void c_plus(complex a,complex b,complex *c)
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{
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c->real = a.real + b.real;
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c->imag = a.imag + b.imag;
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}
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void c_sub(complex a,complex b,complex *c)
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{
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c->real = a.real - b.real;
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c->imag = a.imag - b.imag;
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}
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void c_mul(complex a,complex b,complex *c)
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{
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c->real = a.real * b.real - a.imag * b.imag;
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c->imag = a.real * b.imag + a.imag * b.real;
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}
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void c_div(complex a,complex b,complex *c)
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{
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c->real = (a.real * b.real + a.imag * b.imag)/(b.real * b.real +b.imag * b.imag);
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c->imag = (a.imag * b.real - a.real * b.imag)/(b.real * b.real +b.imag * b.imag);
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}
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#define SWAP(a,b) tempr=(a);(a)=(b);(b)=tempr
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void Wn_i(int n,int i,complex *Wn,char flag)
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{
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Wn->real = iot_cos(2*PI*i/n);
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if(flag == 1)
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Wn->imag = -iot_sin(2*PI*i/n);
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else if(flag == 0)
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Wn->imag = -iot_sin(2*PI*i/n);
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}
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void fft(int N,complex f[])
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{
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complex t,wn;
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int i,j,k,m,n,l,r,M;
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int la,lb,lc;
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/*----M=log2(N)----*/
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for(i=N,M=1;(i=i/2)!=1;M++);
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for(i=1,j=N/2;i<=N-2;i++)
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{
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if(i<j)
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{
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t=f[j];
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f[j]=f[i];
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f[i]=t;
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}
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k=N/2;
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while(k<=j)
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{
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j=j-k;
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k=k/2;
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}
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j=j+k;
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}
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/*----FFT----*/
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for(m=1;m<=M;m++)
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{
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la=iot_pow(2,m); //la=2^m代表第m级每个分组所含节点数
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lb=la/2; //lb代表第m级每个分组所含碟形单元数
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//同时它也表示每个碟形单元上下节点之间的距离
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/*----碟形运算----*/
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for(l=1;l<=lb;l++)
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{
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r=(l-1)*iot_pow(2,M-m);
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for(n=l-1;n<N-1;n=n+la) //遍历每个分组，分组总数为N/la
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{
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lc=n+lb; //n,lc分别代表一个碟形单元的上、下节点编号
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Wn_i(N,r,&wn,1);//wn=Wnr
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c_mul(f[lc],wn,&t);//t = f[lc] * wn复数运算
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c_sub(f[n],t,&(f[lc]));//f[lc] = f[n] - f[lc] * Wnr
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c_plus(f[n],t,&(f[n]));//f[n] = f[n] + f[lc] * Wnr
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}
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}
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}
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}
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//傅里叶逆变换
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void ifft(int N,complex f[])
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{
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int i=0;
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conjugate_complex(N,f,f);
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fft(N,f);
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conjugate_complex(N,f,f);
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for(i=0;i<N;i++)
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{
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f[i].imag = (f[i].imag)/N;
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f[i].real = (f[i].real)/N;
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}
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} |