数字信号处理DSP毕业论文 第22页

#include <math.h>

void firwin(n,band,fln,fhn,wn,h)

int n,band,wn;

double fln,fhn,h[];

{int i,n2,mid;

double s,pi,wc1,wc2,beta,delay;

double window();

beta=0.0;

if(wn==7)

{printf(“input beta parameter of Kaiser window (3<beta<10)\n”);

scanf(“%lf”,&beta);}

pi=4.0*atan(1.0);

if((n%2)==0)

{n2=n/2-1;

mid=1;}

else

{n2=n/2;

mid=0;}

delay=n/2.0;

wc1=2.0*pi*fln;

if(band>=3) wc2=2.0*pi*fhn;

switch(band)

{case1:

{for(i=0;i<=n2;i++)

{s=i-delay;

h[i]=(sin(wc1*s)/(pi*s))*window(wn,n+1,i,beta);

h[n-i]=h[i];}

if(mid==1) h[n/2]=wc1/pi;

break;}

case2:

{for(i=0;i<=n2;i++)

{s=i-delay;

h[i]=(sin(pi*s)-sin(wc1*s))/(pi*s);

h[i]=h[i]*window(wn,n+1,i,beta);

h[n-i]=h[i];}

if(mid==1) h[n/2]=1.0-wc1/pi;

break;}

case3:

{for(i=0;i<=n2;i++)

{s=i-delay;

h[i]=(sin(wc2*s)-sin(wc1*s))/(pi*s);

h[i]=h[i]*window(wn,n+1,i,beta);

h[n-i]=h[i];}

if(mid==1) h[n/2]=(wc2-wc1)/pi;

break;}

case4:

{for(i=0;i<=n2;i++)

{s=i-delay;

h[i]=(sin(wc1*s)+sin(pi*s)-sin(wc2*s))/(pi*s);

h[i]=h[i]*window(wn,n+1,i,beta);

h[n-i]=h[i];}

if(mid==1) h[n/2]=(wc1+pi-wc2)/pi;

break;}

}

}

static double window(type,n,i,beta)

int i,n,type;

double beta;

{int k;

double pi,w;

double Kaiser();

pi=4.0*atan(1.0);

w=1.0;

switch(type)

{case1:

{w=1.0;

break;}

case2:

{k=(n-2)/10;

if(i<=k)

w=0.5*(1.0-cos(i*pi/(k+1)));

if(i>n-k-2)

w=0.5*(1.0-cos((n-i-1)*pi/(k+1)));

break;}

case3:

{w=1.0-fabs(1.0-2*i/(n-1.0));

break;}

case4:

{w=0.5*(1.0-cos(2*i*pi/(n-1)));

break;}

case5:

{w=0.54-0.46*cos(2*i*pi/(n-1));

break;}

case6:

{w=0.42-0.5*cos(2*i*pi/(n-1))+0.08*cos(4*i*pi/(n-1));

break;}

case7:

{w=Kaiser(i,n,beta);

break;}

}

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