function y=DQPSK(N)
%本程序生成DQPSK信號基帶星座圖映射序列
%參數(shù)聲明
%    N    碼元數(shù)目


%函數(shù)體
M=2*N;
x=randint(1,M,2);
I=x(1:2:2*N);
Q=x(2:2:2*N);
I_data=zeros(1,N);
Q_data=zeros(1,N);
I_data(1)=1;
Q_data(1)=0;
theta=zeros(1,N);
theta(1)=0;
%定義相位轉(zhuǎn)移序列
for i=2:N
    if I(i)==1&Q(i)==1
        fai=pi/4;
    elseif I(i)==0&Q(i)==1
        fai=3*pi/4;
    elseif I(i)==0&Q(i)==0
        fai=-3*pi/4;
    elseif I(i)==1&Q(i)==0
        fai=-pi/4;
    end
    theta(i)=theta(i-1)+fai;
    while theta(i)>pi
        theta(i)=theta(i)-2*pi;
    end
    while theta(i)<-pi
        theta(i)=theta(i)+2*pi;
    end    
end
I_data=cos(theta);
Q_data=sin(theta);
y=I_data+j*Q_data;