%...assume the symbol T=1
clear all
close all
bit_in = randint(1e3, 1, [0 1]);
bit_I  = bit_in(1:2:1e3);
bit_Q  = bit_in(2:2:1e3);

data_in=-2*bit_in+1;
data_I = -2*bit_I+1;
data_Q = -2*bit_Q+1;

t=(1:1:1e3);
figure(1)
subplot(3,1,1);stem(t,data_in);axis([0 20 -1 1]);title('基帶源信號');grid on;
t=(1:2:1e3);
subplot(3,1,2);stem(t,data_I);axis([0 20 -1 1]);title('I支路源信號');grid on;
t=(2:2:1e3);
subplot(3,1,3);stem(t,data_Q);axis([0 20 -1 1]);title('Q支路源信號');grid on;

data_in1=repmat(data_in',20,1);%data_in'為data_in的共軛轉置,repmat為把data_in'重排成(20*1)的數組,
data_I1=repmat(data_I',20,1);
data_Q1=repmat(data_Q',20,1); 

f1=1;
t=0:0.1:1e3;
in_rc=data_in1.*cos(2*pi*f1*t);
I_rc=data_I1.*cos(2*pi*f1*t);
Q_rc=data_Q1.*sin(2*pi*f1*t);
QPSK_rc=I_rc+(-Q_rc);

figure(2)
subplot(3,1,1);plot(t,I_rc);axis([0 le3 -3 3]);title('I支路載波調制后信號');grid on;
subplot(3,1,2);plot(t,Q_rc);axis([0 le3 -3 3]);title('Q支路載波調制后信號');grid on;
subplot(3,1,3);plot(t,QPSK_rc);axis([0 le3 -3 3]);title('QPSK已調信號');grid on;