巴特沃斯低通滤波器(C语言)

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能实行，c语言不能显示图像，但是你要懂得如何用c调用matlab，过程比较复杂，这个程序任何参数都可以用，不限制

#include

double calcN(double fp,double ap, double fs, double as)

{

double i = pow(10,(as/10)) - 1;

double tmp = ap/10;

double j = pow(10,tmp) - 1;

double k = log10((i/j));

double t = log10(fs/fp);

double N = 0.5*k/t + 1;

return N;

};

int main(void)

{

int fp,ap,fs,as;

printf("请输入fp:");

scanf("%d", &fp);

printf("请输入ap:");

scanf("%d", &ap);

printf("请输入fs:");

scanf("%d", &fs);

printf("请输入as:");

scanf("%d", &as);

int f = calcN(fp, ap, fs, as);

printf("N=%d\n",f);

char lin[40];

char *str = "N=\0";

lin[0]='\0';

char in[4];

itoa(f,in,10);

strcat(lin,str);

strcat(lin,in);

strcat(lin, ";");

/////////////////////////////////////////////////////////// Engine *ep;

if(!(ep = engOpen(NULL)))

{

printf("open failed! please try again\n");

}

engSetVisible(ep, 0);

//mxArray *xx = mxCreateDoubleMatrix(1,N,mxREAL);

// mxArray *yy = mxCreateDoubleMatrix(1,N,mxREAL);

// memcpy(mxGetPr(xx),N*sizeof(double));

// memcpy(mxGetPr(yy),N*sizeof(double));

// engPutVariable(ep,"xx",xx);

//engPutVariable(ep,"yy",yy);

engEvalString(ep, "n=0:0.01:2;");

engEvalString(ep, lin);

engEvalString(ep, "[z,p,k]=buttap(N);");

engEvalString(ep, "[b,a]=zp2tf(z,p,k);");

engEvalString(ep, "[H,w]=freqs(b,a,n);");

engEvalString(ep, "magH=(abs(H)).^2;");

engEvalString(ep, "plot(w,magH);");

engEvalString(ep, "axis([0 2 0 1])");

engEvalString(ep, "xlabel('w/wc');");

engEvalString(ep, "ylabel('|H(jw)|^2');");

engEvalString(ep, "title('Butterworth analog filter prototype');");

engEvalString(ep, "grid;"); getchar();

//mxDestroyArray(xx);

// mxDestroyArray(yy);

// engClose(ep);

return 0;

}