matlab help on frequency spectrum plot

[abhinaykundur]

hi i'm writing a code for modulating a triangle wave with a sine carrier and plot its frequency spectrum. i should get my spectrum at +fc and -fc but i got them at +2fc and -2fc. my code is

clc;close all;
%td=input('enter a time delay:');
%k=ceil(1/td);
%n=1;
T=0.1;
%p=ceil(k*T);
%disp(p);
%I = zeros(p,1);
%I(1)=0;
%beta=4;
%disp(k);
alpha0=3.5;
f=100e3;
fc = 1e6;
%t=linspace(0,T,p);
p=3.*(fc+2.*f);
disp(p);
t=linspace(0,T,p);
alpha_dc=alpha0*rectpuls(t-0.05,0.1);
plot(t,alpha_dc);
ylim([0 5]);
%plot(t,alpha_dc);
%xlabel('alpha');
%ylabel('amplitude');
%x = 0:0.0000005:2*pi;
alpha_ac=0.25*sawtooth((2*pi*f*t),0.5);
figure;plot(t,alpha_ac);xlabel('\t'); ylabel('x2(t)');
%grid
%xlim([0 1e-5]);
%alpha = zeros(p,1);
alpha=alpha_dc+alpha_ac;
figure;plot(t,alpha);
xlim([0 1e-5]);
%axis([0 1e-5 -1 1]);
C = cos(2*pi*fc*t);
M = C.*alpha;
I = C+M;
%subplot(1,2,1);
%figure;
%plot(alpha(1,,I);
%xlabel('alpha');
%ylabel('intensity');
figure;
plot(t,I);
xlim([0 0.05/100]);
%J=zeros(p,1);
%N=length(I);
int=t(2)-t(1);
disp(int);
%X=abs(fft(I,20*N));
%X=(fftshift(X));
X=zeros(p,1);
X = fftshift(abs(fft(I,5*length(I))));
w = linspace(-1/int,1/int,length(X));
%f=(-(N-1)/2N-1)/2);
%win=hamming(2048);
%J=win.*X(1:length(win));
figure, plot(w,X);
xlim([-5e6 5e6]);
also my amplitude in the frequency spectrum shoots up even when all my amplitudes are less than 4 V. please help me thank you