function [ck]=vect_c(s1l,s2l,L,N,Tb,Be,tk);
sum=0;
for l=-2*L:2*L
    sum1=0;
    sum2=0;
    for k=max(-L,l-L):min(L,l+L)
        sum1=sum1+conj(s1l(k-l+L+1))*s1l(k+L+1);
        sum2=sum2+conj(s2l(k-l+L+1))*s2l(k+L+1);
    end
    c1l=sum1;
    c2l=sum2;
    cl=c1l-c2l;
    f=l/(N*Tb);
    ff=2.43*f/Be;
    Hef=945/(j*ff.^5+15*ff.^4-105*j*ff.^3-420*ff.^2+945*j*ff+945);    
    sum=sum+cl*abs(Hef)*exp(j*2*pi*l*tk/(N*Tb));
end
ck=sum;%ck是隨K變化的數(shù)組