function [t,y]=modulate_to_high(x1,x2,f,hf)
yo1=zeros(1,length(x1)*hf/f*10);
yo2=zeros(1,length(x2)*hf/f*10);
n=1:length(yo1);
yo1(n)=x1(floor((n-1)/(hf/f*10))+1);
yo2(n)=x1(floor((n-1)/(hf/f*10))+1);
t=(1:length(yo1))/hf*f/10;
y=yo1.*cos(2*pi*hf*t)-yo2.*sin(2*pi*hf*t);