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+//IIR filter design
+//Design of chebyshev IIR filter with following specifications
+fp1=1.6;fp2=1.8;fs1=3.2;fs2=4.8;//pass band edges
+Ap=2;As=20;S=12;
+s=%s;z=%z;
+//(a)Indirect Bilinear design
+W=2*%pi*[fp1 fp2 fs1 fs2]/S
+C=2;
+omega=2*tan(0.5*W');//prewarping each band edge frequency
+epsilon=sqrt(10^(0.1*Ap)-1);
+n=acosh(((10^(0.1*As)-1)/epsilon^2)^1/2)/(acosh(fs1/fp1));
+n=ceil(n)
+alpha=(1/n)*asinh(1/epsilon);
+for i=1:n
+    B(i)=(2*i-1)*%pi/(2*n);
+end
+for i=1:n
+    p(i)=-sinh(alpha)*sin(B(i))+%i*cosh(alpha)*cos(B(i));
+end
+Qs=1;
+for i=1:n
+    Qs=Qs*(s-p(i))
+end
+Qo=0.1634;
+HPS=Qo/Qs
+HBPS=horner(HPS,(s^2+1.5045^2)/(s*1.202))
+HZ=horner(HBPS,2*(z-1)/(z+1))
+f=0:0.001:0.5;
+HZF=abs(horner(HZ,exp(%i*2*%pi*f')));
+HBPF=abs(horner(HBPS,%i*2*%pi*f'));
+a=gca();
+plot2d(f,HZF);
+plot2d(f,HBPF);
+xlabel('Analog Frequency');
+ylabel('magnitude');
+xtitle('band pass filter designed by the bilinear transformation');
+\ No newline at end of file