function f=mimo_corr(anglespread,angle,d,M)  
%角度擴展 平均到達角 天線間隔與波長之比 天線個數
L=1000;
anglespread1=720;
c=0;

%clear i;
p=zeros(1,L);
fai=zeros(1,L);
fai1=zeros(1,L);
FAI=zeros(1,L);
matrix1=zeros(M,1);
matrix2=zeros(1,M);
correlation1=zeros(M,M);
correlation2=zeros(M,M);
correlation=zeros(M,M);

for m=1:L
    fail(1,m)=angle-anglespread1+2*anglespread1*m/L;
    fai(1,m)=2*pi*(angle-anglespread1+2*anglespread1*m/L)/360;
    
    FAI(1,m)=d*sin(fai(1,m));
end

for m=1:L
    
    p(1,m)=1/(anglespread*sqrt(2))*exp(-sqrt(2)*abs(fail(1,m)-angle)/anglespread)*2*anglespread1/L;
end

for m=1:L
    c=p(1,m)+c;
end
c;

for m=1:L
    for n=1:M
        matrix1(n,1)=exp(i*FAI(m)*2*pi*(n-1));
    end
    matrix2=matrix1';
    correlation1=matrix1*matrix2*p(1,m);
    correlation2=correlation1+correlation2;
end

for m=1:M
    for n=1:M
        correlation(m,n)=abs(correlation2(m,n))/c;
    end
end
f=correlation;