clear all
close all
clc
% Experiment 2..... Aliasing Effect
f1=10;w1=2*pi*f1;
f2=20;w2=2*pi*f2;
f3=30;w3=2*pi*f3;

L=100; % Length of signal
fs=40; % Sampling freq
Ts=1/fs;
t=(0:(L-1))*Ts;

x1=sin(w1*t);
x2=sin(w2*t);
x3=sin(w3*t);

x=x1+x2+x3;

subplot(2,1,1)
plot(t,x)
xlabel("time t")
ylabel("x(t)")
title("continuous signal x(t)")

subplot(2,1,2)
stem(t,x)
xlabel("time nTs")
ylabel("x(nTs)")
title("sampled signaL x(nTs)")




Y=fft(x);
subplot(3,1,1)
freq1=(0:L-1)*fs/L;
plot(freq1, abs(Y));
xlabel("frequency")
ylabel("magnitude")
title("fft spectrum of x(t)")

subplot(3,1,2)
freq2=(-L/2:L/2-1)*fs/L;
plot(freq2, abs(fftshift(Y)));
xlabel("freq")
ylabel("mag")
title("fft spectrum in +ve and -ve frequencies")

subplot(3,1,3)
freq2=(-L/2:L/2-1)*fs/L;
plot(freq2, abs(fftshift(Y)));
xlabel("freq")
ylabel("mag")
title("fft spectrum in +ve frequencies")
axis([0 fs/2 0 max(abs(Y))])