%...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_I1=repmat(data_I',20,1);
data_Q1=repmat(data_Q',20,1);

for i=1:1e4
    data_in2(i)=data_in1(i);
    data_I2(i)=data_I1(i);
    data_Q2(i)=data_Q1(i);
end;

t=0:0.1:1e3-0.1;
f=0:0.1:1;
xrc=0.5+0.5*cos(pi*f);
data_in2_rc=conv(data_in2,xrc)/5.5;
data_I2_rc=conv(data_I2,xrc)/5.5;
data_Q2_rc=conv(data_Q2,xrc)/5.5;

f1=1;
t1=0:0.1:1e3+0.9;
in_rc=data_in2_rc.*cos(2*pi*f1*t1);
I_rc=data_I2_rc.*cos(2*pi*f1*t1);
Q_rc=data_Q2_rc.*sin(2*pi*f1*t1);
QPSK_rc=(sqrt(1/2).*I_rc+sqrt(1/2).*Q_rc);

figure(2)
subplot(3,1,1);plot(t1,data_in2_rc);axis([0 20 -3 3]);title('基帶信號');grid on;
 subplot(3,1,2);plot(t1,data_I2_rc);axis([0 20 -3 3]);title('I支路');grid on;
 subplot(3,1,3);plot(t1,data_Q2_rc);axis([0 20 -3 3]);title('Q支路');grid on;
 
 figure(3)
 subplot(3,1,1);plot(data_in2);axis([0 2e2+0.9 -3 3]);title('基帶信號');grid on;
subplot(3,1,2);plot(data_I2);axis([0 2e2+0.9 -3 3]);title('I支路');grid on;
subplot(3,1,3);plot(data_Q2);axis([0 2e2+0.9 -3 3]);title('Q支路');grid on;

figure(4)
subplot(3,1,1);plot(t1,I_rc);axis([0 2e1+0.9 -3 3]);title('I支路載波調制后信號');grid on;
subplot(3,1,2);plot(t1,Q_rc);axis([0 2e1+0.9 -3 3]);title('Q支路載波調制后信號');grid on;
subplot(3,1,3);plot(t1,QPSK_rc);axis([0 2e1+0.9 -3 3]);title('QPSK已調信號');grid on;

 
 
%%..demodulation
I_demo=QPSK_rc.*cos(2*pi*f1*t1);
Q_demo=QPSK_rc.*sin(2*pi*f1*t1);

I_recover=conv(I_demo,xrc);
Q_recover=conv(Q_demo,xrc);
I=I_recover(11:10010);
Q=Q_recover(11:10010);
t2=0:0.05:1e3-0.05;
t3=0:0.1:1e3-0.1;

data_recover=[];
for i=1:20:10000
    data_recover=[data_recover I(i:1:i+19) Q(i:1:i+19)];
end;

ddd = -2*bit_in+1;
ddd1=repmat(ddd',10,1);
for i=1:1e4
    ddd2(i)=ddd1(i);
end

figure(5)
subplot(4,1,1);plot(t3,I);axis([0 20 -6 6]);title('I支路相干解調后信號');grid on
subplot(4,1,2);plot(t3,Q);axis([0 20 -6 6]);title('Q支路相干解調后信號');grid on
subplot(4,1,3);plot(t2,data_recover);axis([0 20 -6 6]);title('并串變換后輸出');grid on
subplot(4,1,4);plot(t,ddd2);axis([0 20 -6 6]);title('解調后信號輸出');grid on