FIR WINDOW based (different windows)

%LPF

clc

clear

close all

samp=2000;

n=0:1/samp:1;

x=cos(2*pi*100*n)+cos(2*pi*500*n)+cos(2*pi*700*n);

N=66;

W=.4;

w=window(@blackmanharris,N+1);%blackman harris window

figure

subplot 121, plot(1:N+1,w);

b = fir1(N, W, 'low',w);

[h,o]=freqz(b,1,256);

subplot 122, plot(o/pi, 20*log10(abs(h)));

y=filter(b,1,x);

figure

subplot 211, plot(abs(fft(x)));

subplot 212, plot(abs(fft(y)));

%HPF

clc

clear

close all

samp=2000;

n=0:1/samp:1;

x=cos(2*pi*100*n)+cos(2*pi*500*n)+cos(2*pi*700*n);

N=66;

W=.4;

w=window(@hanning,N+1);%Hanning window

figure

subplot 121, plot(1:N+1,w);

b = fir1(N, W, 'high',w);

[h,o]=freqz(b,1,256);

subplot 122, plot(o/pi, 20*log10(abs(h)));

y=filter(b,1,x);

figure

subplot 211, plot(abs(fft(x)));

subplot 212, plot(abs(fft(y)));

%BPF

clc

clear

close all

samp=2000;

n=0:1/samp:1;

x=cos(2*pi*100*n)+cos(2*pi*500*n)+cos(2*pi*700*n);

N=66;

W=[.4 .6];

w=window(@gausswin,N+1);%Gaussian window

figure

subplot 121, plot(1:N+1,w);

b = fir1(N, W, 'bandpass',w);

[h,o]=freqz(b,1,256);

subplot 122, plot(o/pi, 20*log10(abs(h)));

y=filter(b,1,x);

figure

subplot 211, plot(abs(fft(x)));

subplot 212, plot(abs(fft(y)));

%BSF

clc

clear

close all

samp=2000;

n=0:1/samp:1;

x=cos(2*pi*100*n)+cos(2*pi*500*n)+cos(2*pi*700*n);

N=66;

W=[.4 .6];

w=window(@Hamming,N+1);%Hamming window

figure

subplot 121, plot(1:N+1,w);

b = fir1(N, W, 'stop');%if nothing is given, the DEFAULT WINDOW=Hamming

[h,o]=freqz(b,1,256);

subplot 122, plot(o/pi, 20*log10(abs(h)));

y=filter(b,1,x);

figure

subplot 211, plot(abs(fft(x)));

subplot 212, plot(abs(fft(y)));