# FFT for ideal filters

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Anya ch on 5 Jun 2016
Edited: Anya ch on 5 Jun 2016
Hello everyone,
i have to plot impulse responses for some ideal filters (see the picture)
(lowpass highpass bandpass bandstop)
i was able to plot the lowpass one using this code :
if true
t=-5:.01:5;
x=rectpuls(t,2*0.2);
figure(1)
plot(t,x)
grid
Ts = mean(diff(t));
Fs = 1/Ts;
L = length(x);
ftx = fft(x)/L;
ftxs = fftshift(ftx);
Fv = linspace(-Fn, Fn, L);
figure(2)
plot(Fv, abs(ftxs))
grid
end
Now i want to do the rest, how can i do it ? thanks you !
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### Answers (1)

Weird Rando on 5 Jun 2016
You do realise that the diagram you uploaded is the impulse responses for the ideal filters.
All you need to do is create an array with 1's and 0's at certain points of a and b.
freq = -.5:0.01:.5;
%high pass
b = 0.2;
hp = ones(1,length(freq));
hp(abs(freq)<0.2) = 0;
plot(freq,hp);
%axis([-0.6 0.6 -1 2]);
xlabel('Frequency')
ylabel('Magnitude')
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