iir.c

irr滤波器的实现与仿真供大家参考望有帮助

           /*IIR数字滤波器设计C程序 - 包括图形显示*/

/**********************************************************
IIRD_DF.c-双线性变换法设计IIR数字滤波器
Infinite Impulse Response Digital Filter Design By Double Converting
====================================================
包括1.Lowpass       2.Highpass      3.bandpass三部分，如果有特殊需要
把其他部分删除掉即可。
====================================================
欢迎访问  |     |
|    电子开发网        http://dianzi.net  |
|     |
***********************************************************/
/*#include <windows.h>*/
#include <math.h>
#include <dos.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <conio.h>
#include <graphics.h>

/*COMPLEX STRUCTURE*/
typedef struct{
double real,image;
}COMPLEX;

struct rptr{
double *a;
double *b;
};

#define  PI     (double)(4.0*atan(1.0))
#define  FNSSH(x)    log(x+sqrt(x*x+1))
#define  FNCCH(x)    log(x+sqrt(x*x-1))
#define  FNSH1(x)    (exp(x)-exp(-x))/2
#define  FNCH1(x)    (exp(x)+exp(-x))/2


/***********************************************************************************************/
double *bcg(double ap,double as,double wp,double ws,int *n,double *h,int *type);
struct rptr *bsf(double *c,int ni,double *f1,double *f2,int nf,struct rptr *ptr,int *no);
double *pnpe(double *a,int m,int n,double *b,int *mn);
double *ypmp(double *a,int m,double *b,int n,double *c,int *mn);
void lowpass_input(double *wp,double *ws,double *ap,double *ar,double *f1,double *f2,int *nf);
void highpass_input(double *wp,double *ws,double *ap,double *ar,double *f1,double *f2,int *nf);
void bandpass_input(double *wp,double *ws,double *ap,double *ar,double *f1,double *f2,int *nf);
void draw_image(double *x,int m,char *title1,char *title2,char *xdis1,char *xdis2,int dis_type);
/***********************************************************************************************/

void main(void)
{
double *f1,*f2,*hwdb;
double *h=NULL;
int N,nf,ns,nz,i,j,k,ftype,type;
COMPLEX hwdb1,hwdb2;
double wp,ws,ap,as,jw,amp1,amp2;
char title[80],tmp[20];
struct rptr *ptr=NULL;

/* printf("%lf",PI);
getch();*/
N=500;
f1=(double *)calloc(4,sizeof(double));
f2=(double *)calloc(4,sizeof(double));
hwdb=(double *)calloc(N+2,sizeof(double));
if (hwdb==NULL){
  printf("\\n Not enough memory to allocate!");
  exit(0);
}
printf("\\n1.Lowpass       2.Highpass      3.bandpass");
printf("\\nPlease select the filter type:");
scanf("%d",&ftype);
switch(ftype){
case 1:lowpass_input(&wp,&ws,&ap,&as,f1,f2,&nf);
  break;
case 2:highpass_input(&wp,&ws,&ap,&as,f1,f2,&nf);
  break;
case 3:bandpass_input(&wp,&ws,&ap,&as,f1,f2,&nf);
  break;
default:lowpass_input(&wp,&ws,&ap,&as,f1,f2,&nf);
}

h=bcg(ap,as,wp,ws,&ns,h,&type);
printf("\\nThe analog filter denominator coefficients of Ha(s):");
for(i=0;i<=ns;i++)
  printf("\\nb[%2d]=%16f",i,h[i]);

ptr=bsf(h,ns,f1,f2,nf,ptr,&nz);
printf("\\nThe digital filter coefficients of H(z):");
printf("\\n(a is numerator coefficient. b is denominator coefficient.)");
for(i=0;i<=nz;i++)
  printf("\\na[%2d]=%10f,b[%2d]=%16f",i,ptr->a[i],i,ptr->b[i]);

printf("\\n\\nPress any key to calculate the filter response of H(z)...");
getch();
printf("\\nWaitting for calculating...");


/* Calculate the magnitude-frequency response*/
for(k=0;k<=N;k++){
  jw=k*PI/N;
   hwdb1.real=0;hwdb1.image=0;
   hwdb2.real=0;hwdb2.image=0;
   for(i=0;i<=nz;i++){
    hwdb1.real+=ptr->a[i]*cos(i*jw);
    hwdb2.real+=ptr->b[i]*cos(i*jw);
    hwdb1.image+=ptr->a[i]*sin(i*jw);
    hwdb2.image+=ptr->b[i]*sin(i*jw);
   }
   amp1=(pow(hwdb1.real,2)+pow(hwdb1.image,2));
   amp2=(pow(hwdb2.real,2)+pow(hwdb2.image,2));
   if(amp1==0) amp1=1e-90;
   if(amp2==0) amp2=1e-90;
   hwdb[k]=10*log10(amp1/amp2);
   if(hwdb[k]<-200) hwdb[k]=-200;
   if(k%10==9) printf("*");
}

strcpy(title,"Transfer Property");
if(type==1) strcat(title,"(BW Type) N=");
if(type==2) strcat(title,"(CB Type) N=");
itoa(ns,tmp,10);
strcat(title,tmp);
strcpy(tmp,"PI(rad)");
draw_image(hwdb,N,title,"The Attenuation(dB)","0",tmp,0);

free(ptr->b);
free(ptr->a);
free(h);
free(hwdb);
free(f2);
free(f1);
}

/***************************************************************/
void lowpass_input(double *wp,double *ws,double *ap,double *ar,double *f1,double *f2,int *nf)
{
double fp,fr,fs;
printf("\\nPlease input the Fp,Ap,Fr,Ar,Fs value");
printf("\\nFp,Ap:Passband frequency(Hz) and MAXAttenuation(dB)");
printf("\\nFr,Ar:Stopband frequency(Hz) and MINAttenuation(dB)");
printf("\\nFs is the sample frequency(Hz)       Lowpass filter");
printf("\\nInput parameters Fp,Ap,Fr,Ar,Fs:");
scanf("%lf,%lf,%lf,%lf,%lf",&fp,ap,&fr,ar,&fs);
if((fp>fr)||(*ap>*ar)||(fs<2*fr)){
  do{
   sound(1000);delay(200);nosound();
   printf("Invalid input!  Please  Reinput:");
   scanf("%lf,%lf,%lf,%lf,%lf",&fp,ap,&fr,ar,&fs);
  }while((fp>fr)||(*ap>*ar)||(fs<2*fr));
}
*wp=tan(PI*fp/fs);
*ws=tan(PI*fr/fs);
*f1=-1.0;*(f1+1)=1.0;
*f2=1.0;*(f2+1)=1.0;
*nf=1;
}


/**********************************************************************************************/
void highpass_input(double *wp,double *ws,double *ap,double *ar,double *f1,double *f2,int *nf)
{
double fp,fr,fs;
printf("\\nPlease input the Fp,Ap,Fr,Ar,Fs value");
printf("\\nFp,Ap:Passband frequency(Hz) and MAXAttenuation(dB)");
printf("\\nFr,Ar:Stopband frequency(Hz) and MINAttenuation(dB)");
printf("\\nFs is the sample frequency(Hz)       highpass filter");
printf("\\nInput parameters Fp,Ap,Fr,Ar,Fs:");
scanf("%lf,%lf,%lf,%lf,%lf",&fp,ap,&fr,ar,&fs);
if((fp<fr)||(*ap>*ar)||(fs<2*fp)){
  do{
   sound(1000);delay(200);nosound();
   printf("Invalid input!  Please  Reinput:");
   scanf("%lf,%lf,%lf,%lf,%lf",&fp,ap,&fr,ar,&fs);
  }while((fp<fr)||(*ap>*ar)||(fs<2*fr));
}
*wp=fabs(1/tan(PI*fp/fs));
*ws=fabs(1/tan(PI*fr/fs));
*f1=1.0;*(f1+1)=1.0;
*f2=-1.0;*(f2+1)=1.0;
*nf=1;
}


/**********************************************************************************************/
void bandpass_input(double *wp,double *ws,double *ap,double *ar,double *f1,double *f2,int *nf)
{
double fp1,fp2,fr1,fr2,fs,wp1,wp2,wr1,wr2,cw0,pwp1,pwp2,pws1,pws2;
printf("\\nPlease input the Fp1,Fp2,Ap,Fr1,Fr2,,Ar,Fs value");
printf("\\nFp1,Fp2,Ap:Passband frequency(Hz) and MAXAttenuation(dB)");
printf("\\nFr1,Fr2,Ar:Stopband frequency(Hz) and MINAttenuation(dB)");
printf("\\nFs is the sample frequency(Hz)       bandpass filter");
printf("\\nInput parameters Fp1,Fp2,Ap,Fr1,Fr2,Ar,Fs:");
scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf",&fp1,&fp2,ap,&fr1,&fr2,ar,&fs);
if((fp1>fp2)||(fp1<fr1)||(fp2>fr2)||(*ap>*ar)||(fs<2*fr2)){
  do{
   sound(1000);delay(200);nosound();
   printf("Invalid input!  Please  Reinput:");
   scanf("%lf,%lf,%lf,%lf,%lf,%lf,%lf",&fp1,&fp2,ap,&fr1,&fr2,ar,&fs);
  }while((fp1>fp2)||(fp1<fr1)||(fp2>fr2)||(*ap>*ar)||(fs<2*fr2));
}
wp1=2*PI*fp1/fs;wr1=2*PI*fr1/fs;
wp2=2*PI*fp2/fs;wr2=2*PI*fr2/fs;
cw0=sin(wp1+wp2)/(sin(wp1)+sin(wp2));
pwp1=fabs((cw0-cos(wp1))/sin(wp1));
pws1=fabs((cw0-cos(wr1))/sin(wr1));
pwp2=fabs((cw0-cos(wp2))/sin(wp2));
pws2=fabs((cw0-cos(wr2))/sin(wr2));
if(fabs(pws1-pwp1)<fabs(pws2-pwp2)){
  *wp=pws1;
  *ws=pws1;

}
else{
  *wp=pwp2;
  *ws=pws2;
}
*f1=1.0;*(f1+1)=-2.0*cw0;*(f1+2)=1.0;
*f2=-1.0;*(f2+1)=0.0*cw0;*(f2+2)=1.0;
*nf=2;
}

/**************************************************************************
bcg-Chebyshev 和 Butterworth 型模拟原型传输函数生成子程序
      即程序得到系统函数 H(s).
   输出格式为：

****************************************************************************/
double *bcg(double ap,double as,double wp,double ws,int *n,double *h,int *type)
{
int i,j,k;
double a,c,e,p,q,x,y,wc,cs1,cs2;
COMPLEX *b;
double pp[20];
double xs[8][8]={{1.0},
{1.0,1.41421356},
{1.0,2.0,2.0},
{1.0,2.61312593,3.41421356,2,61312593},
{1.0,3.23606789,5.23606789,5.23606789,3.23606789},
{1.0,3.86370331,7.46410162,9.14162017,7.46410162,3.86370331},
{1.0,4.49395921,10.09783468,14.59179389,14.59579389,10.09783468,4.49395921},
{1.0,5.12583090,13.13707118,21.84615097,25.68835593,21.84615097,13.13707118,5.12583090}};

printf("\\nTYPE        1.Butterworth        2.Chebyshev?(1/2):");
scanf("%d",type);
if(*type==2){
  c=sqrt(pow(10,as/10.0)-1.0);
  e=sqrt(pow(10,ap/10.0)-1.0);
  *n=(int)(fabs(FNCCH(c/e)/FNCCH(ws/wp))+0.99999);
  b=(COMPLEX*)calloc(*n+2,sizeof(COMPLEX));
  if(b==NULL){
   printf("\\nNot enough memory to allocate!");
   exit(0);
  }
  wc=wp;
  a=pow(wc,(*n))/(e*pow(2.0,(*n)-1));
  q=1/e;
  x=FNSSH(q)/(*n);
  for(i=0;i<*n;i++){
   y=(2.0*i+1.0)*PI/(2.0*(*n));
   (b+i)->real=-wc*FNSH1(x)*sin(y);
   (b+i)->image=-wc*FNCH1(x)*cos(y);
  }
}
else{
  c=(pow(10.0,(0.1*ap))-1.0)/(pow(10.0,(0.1*as))-1.0);
  *n=(int)(fabs(log(c)/log(wp/ws)/2.0)+0.99999);
  b=(COMPLEX *)calloc(*n+2,sizeof(COMPLEX));
  if(b==NULL){
   printf("\\nNot enough memory to allocate!");
   exit(0);
  }
  wc=wp/pow(pow(10.0,0.1*ap)-1.0,1.0/(2.0*(*n)));
  a=pow(wc,(double)(*n));
  for(i=0;i<*n;i++){