t11=0; t12=1;
t21=0; t22=2;
t1=t11:0.001:t12;
ft1=2*rectpuls(t1-0.5, 1);%rectpuls(t1-0.5, 1)的意思是：幅值为1，宽度为1的方波信号，t1-0.5的意思是方波的中心点为t1-0.5，即0.5

t2=t21:0.001:t22;
ft2=t2;
t3=(t11+t21) : 0.001 : (t12+t22);%卷积积分的区间[t11+t21, t12+t22]
ft3=conv(ft1, ft2);
ft3=ft3*0.001;

plot(t3, ft3);
title('ft1(t) * ft2(t)');