I'm trying implement a IIR filter.I know the IIR filter come from that equation:

and i found that for high pass filter the coefficients are:

where fc = cut freq.

here my matlab code:

fs = 1000;
fc=0.3;
r=exp(-2*pi*fc);
a = [(1+r)/2 -(1+r)/2];
b= [1 -r];
n = 0:1/(fs):20;
n1 = 1024;
x1 = cos(0.3*2*pi.*n);
x2 = cos(0.8*2*pi.*n);
%plot(n,x1);
%hold on
%plot(n,x2);
%hold on
%plot(n,x1+x2);
%aux = fft((x1+x2),n1);
%aux = aux(1:n1/2);
%f = (0:n1/2-1)*(fs/n1);
%length(f)
%legend('x1[n]','x2[n]','x1+x2')
%plot(f,abs(aux));
%hold on

y = filter([0.5759 -0.5759],[1 -0.1518] , x1+x2);
plot(n,y,'r-',n,x2,'b--',n,x1,'g-.');
grid
%axis([0 100 -1.2 4]);
ylabel('Amplitude');
xlabel('Time index n');
legend('y[n]','x2[n]','x1[n]')

the commented parts are from FFT part of program and it's working well but the filter function isn't working. Help me plz and sorry about my english.

I'm trying implement an IIR filter. I know the IIR filter come from that equation:

and i found that for high pass filter the coefficients are:

where fc = cut freq.

here my matlab code:

fs = 1000;
fc=0.3;
r=exp(-2*pi*fc);
a = [(1+r)/2 -(1+r)/2];
b= [1 -r];
n = 0:1/(fs):20;
n1 = 1024;
x1 = cos(0.3*2*pi.*n);
x2 = cos(0.8*2*pi.*n);
%plot(n,x1);
%hold on
%plot(n,x2);
%hold on
%plot(n,x1+x2);
%aux = fft((x1+x2),n1);
%aux = aux(1:n1/2);
%f = (0:n1/2-1)*(fs/n1);
%length(f)
%legend('x1[n]','x2[n]','x1+x2')
%plot(f,abs(aux));
%hold on

y = filter([0.5759 -0.5759],[1 -0.1518] , x1+x2);
plot(n,y,'r-',n,x2,'b--',n,x1,'g-.');
grid
%axis([0 100 -1.2 4]);
ylabel('Amplitude');
xlabel('Time index n');
legend('y[n]','x2[n]','x1[n]')

the commented parts are from FFT part of program and it's working well but the filter function isn't working. Help me plz and sorry about my english.

I'm trying implement a IIR filter.I know the IIR filter come from that equation:

and i found that for high pass filter the coefficients are:

where fc = cut freq.

here my matlab code:

fs = 1000;
fc=0.3;
r=exp(-2*pi*fc);
a = [(1+r)/2 -(1+r)/2];
b= [1 -r];
n = 0:1/(fs):20;
n1 = 1024;
x1 = cos(0.3*2*pi.*n);
x2 = cos(0.8*2*pi.*n);
%plot(n,x1);
%hold on
%plot(n,x2);
%hold on
%plot(n,x1+x2);
%aux = fft((x1+x2),n1);
%aux = aux(1:n1/2);
%f = (0:n1/2-1)*(fs/n1);
%length(f)
%legend('x1[n]','x2[n]','x1+x2')
%plot(f,abs(aux));
%hold on

y = filter([0.5759 -0.5759],[1 -0.1518] , x1+x2);
plot(n,y,'r-',n,x2,'b--',n,x1,'g-.');
grid
%axis([0 100 -1.2 4]);
ylabel('Amplitude');
xlabel('Time index n');
legend('y[n]','x2[n]','x1[n]')

the commented parts are from FFT part of program and it's working well but the filter function isn't working. Help me plz and sorry about my english.

I'm trying implement a IIR filter.I know the IIR filter come from that equation:

and i found that for high pass filter the coefficients are:

where fc = cut freq.

here my matlab code:

fs = 1000;
fc=0.3;
r=exp(-2*pi*fc);
a = [(1+r)/2 -(1+r)/2];
b= [1 -r];
n = 0:1/(fs):20;
n1 = 1024;
x1 = cos(0.3*2*pi.*n);
x2 = cos(0.8*2*pi.*n);
%plot(n,x1);
%hold on
%plot(n,x2);
%hold on
%plot(n,x1+x2);
%aux = fft((x1+x2),n1);
%aux = aux(1:n1/2);
%f = (0:n1/2-1)*(fs/n1);
%length(f)
%legend('x1[n]','x2[n]','x1+x2')
%plot(f,abs(aux));
%hold on

y = filter([0.5759 -0.5759],[1 -0.1518] , x1+x2);
plot(n,y,'r-',n,x2,'b--',n,x1,'g-.');
grid
%axis([0 100 -1.2 4]);
ylabel('Amplitude');
xlabel('Time index n');
legend('y[n]','x2[n]','x1[n]')

the commented parts are from FFT part of program and it's working well but the filter function isn't working. Help me plz and sorry about my english.