Creating low pass filter

How do I create anti aliasing low pass filter shown in the figure? So far I have coded root raised cosine in frequency domain:

%Generating Root Raised Cosine Pulse in Frequency Domain
T=0.1*10^-3; %symbol period
alpha=0.5; %roll-off factor
N=10/T;
f=linspace(-1/T,1/T,N+1);
% Generation of the raised cosine pulse using the formula in Lecture
Q=zeros(size(f));
Q(abs(f)<=1/2/T*(1-alpha))=T;
Q(abs(f)<=1/2/T*(1+alpha) & abs(f)>=1/2/T*(1-alpha))=T/2*(1- sin(T/2/alpha*(2*pi*abs(f... (abs(f)<=1/2/T*(1+alpha) & abs(f)>=1/2/T*(1-alpha)))-pi/T)));
    %Plot
plot(f,sqrt(Q));
xlabel('frequency[Hz]', 'FontSize', 11);
ylabel('Amplitude', 'FontSize', 11);
title('Root Raised Cosine Pulse', 'Fontsize', 11);
grid on
axis square;
hold on;
%Keep when comparing graphs with different roll-off factors

[Shyngys Serikov]

Answer 1

[Sufiyan]

You can try this

q_time = ifftshift(ifft(Q, 'symmetric')); % Inverse FFT with ifftshift
t = linspace(-5*T, 5*T, N);

plot(t, q_time);
xlabel('Time [s]', 'FontSize', 11);
ylabel('Amplitude', 'FontSize', 11);
title('Time Domain', 'Fontsize', 11);
grid on;
axis square;