%Gen_Jake
% sum of sinusoids simulation model (improved jakes model)
function Zt=Gen_Jake2(Fd,Ts,Block_Num, seed)
%for one simulation, only generate 1 thetha, M phi1 and M phi2
%Fd: Doppler frequency

rand('state',seed);
M=32; %# of sinusoids
thetha=(rand-0.5)*2*pi; %uniform distributed in [-pi,pi)

phi1=(rand(1,M)-0.5)*2*pi;
phi2=(rand(1,M)-0.5)*2*pi;

%ic=[1:Block_Num]';
%t=ic.*Ts; % time

Tstart=ceil(M/Fd/Ts+0.9*rand(1)*M/Fd/Ts);  %Avoid unstable period and set a random start point
%Tstart=ceil(0.9*rand(1)*M/Fd/Ts);
t = Tstart:Tstart+Block_Num-1;
t = t.*Ts;
Zc=zeros(1, Block_Num);
Zs=zeros(1, Block_Num);

for nn=1:M
    alpha=(2*pi*nn-pi+thetha)/(4*M);
    Zc=Zc+cos(2*pi*Fd.*t*cos(alpha)+phi1(nn));
    Zs=Zs+cos(2*pi*Fd.*t*sin(alpha)+phi2(nn));
end

Zt=sqrt(2/M).*complex(Zc,Zs);

%May be omitted
norm=sqrt(mean(abs(Zt).^2));
Zt=Zt/norm;
%Zt=Zt/sqrt(2);