DSP实现FFT的代码.doc

DSP实现的方法 /#include DSP281x_Device.h / DSP281x Headerfile Include File/#include DSP281x_Examples.h / DSP281x Examples Include File#include #include #include #define pi atan(1.0)*4 /计算PI的值typedef struct /定义表示复数的结构体 float real; float imag;FUSHU;FUSHU x1024;int w1024;FUSHU FUCHENG(FUSHU b1,FUSHU b2) /复数相乘函数 FUSHU b3; b3.real=b1.real*b2.real-b1.imag*b2.imag; b3.imag=b1.real*b2.imag+b1.imag*b2.real; return(b3);void FFT(FUSHU *xin,int N) /FFT运算 int m,LH,I,k,J,M,K; float p,ps ; int B,N1; FUSHU w,T; M=10;/对应N值为 /下面是倒序的程序 LH=N/2; J=LH; N1=N-2; /*变址运算*/ for(I=1;I=N1;I+) if(I=K) J=J-K; K=K/2; J=J+K; /下面是DIT-FFT运算程序 for(m=1;m=M;m+) B=pow(2.0,m-1); for(J=0;J=B-1;J+) p=pow(2.0,M-m)*J; ps=2*pi/N*p; w.real=cos(ps); w.imag=-sin(ps); for(k=J;k=N-1;k=k+pow(2.0,m) T=FUCHENG(xink+B,w); xink+B.real=xink.real-T.real; xink+B.imag=xink.imag-T.imag; xink.real=xink.real+T.real; xink.imag=xink.imag+T.imag; void IFFT(FUSHU *xin,int N) /IFFT运算 int m,LH,I,k,J,M,K; float p,ps ; int B,N1; FUSHU w,T; M=10;/对应N值为 /下面是倒序的程序 LH=N/2; J=LH; N1=N-2; /*变址运算*/ for(I=1;I=N1;I+) if(I=K) J=J-K; K=K/2; J=J+K; for(m=1;m=M;m+) B=pow(2.0,m-1); for(J=0;J=B-1;J+) p=pow(2.0,M-m)*J; ps=2*pi/N*p; w.real=cos(ps); w.imag=sin(ps);/与FFT符号相反 for(k=J;k=N-1;k=k+pow(2.0,m) T=FUCHENG(xink+B,w); xink+B.real=xink.real-T.real; xink+B.imag=xink.imag-T.imag; xink.real=xink.real+T.real; xink.imag=xink.imag+T.imag; for(k=0;kN;k+)/比FFT多乘了一个常数因子/N xink.real=xink.real/N; xink.imag=xink.imag/N; int main() int n; for(n=0;n1024;n+) /输入波形x(t) = cos(2*pi* 100*t) xn.real=cos(2*pi*100*n/1024); /采样频率为kHz xn.imag=0; FFT(x,1024);/进行FFT运算 for ( n=0;n1024;n+ ) wn=sqrt(xn.real*xn.real+xn.imag*xn.imag);/幅度谱 IFFT(x,1024);/进行IF