rayleigh.m

关于无线信道的多普勒谱 无线信道中的多普勒谱有一种经典谱请解释产生这种谱形状的机理；

function [sys,x0,str,ts]=rayleigh(t,x,u,flag,N)
switch flag,
    case 0
        [sys,x0,str,ts]=mdlInitializeSizes;
    case 3
        sys=mdlOutputs(t,x,u);
    case {1,2,4,9}
        sys=[];
    otherwise
        error(['Unhandled flag= ',num2str(flag)]);
end
function [sys,x0,str,ts]=mdlInitializeSizes()
sizes=simsizes;
sizes.NumContStates=0;         
sizes.NumDiscStates=0;         
sizes.NumOutputs=512;         
sizes.NumInputs=0;          
sizes.DirFeedthrough=0;        
sizes.NumSampleTimes=1;      
sys=simsizes(sizes);           
str=[];                        
x0=[];                         
ts=[0.25 0];                   
%函数的初始化结束
%--------------------------------------------------------------------------

function sys=mdlOutputs(t,x,u)  
N=512;                        
fm=100;                       
delta_f=2*fm/(N-1);           
T=1/delta_f;                    
I_input_time=randn(1,N);      
Q_input_time=randn(1,N);      

I_input_freq=fft(I_input_time);     
Q_input_freq=fft(Q_input_time);   

for j=2:N-1
   f(j)=-100+(j-1)*200/(N-1);
   SEZ(j) = 1.5/(pi*fm*sqrt(1-(f(j)/fm)^2));
end
f(1)=-99.99;f(N)=99.99;
SEZ(1) = 1.5/(pi*fm*sqrt(1-(f(1)/fm)^2));
SEZ(N) = 1.5/(pi*fm*sqrt(1-(f(N)/fm)^2));    

I_output_freq = I_input_freq.* sqrt(SEZ); 
Q_output_freq = Q_input_freq.* sqrt(SEZ); 

I_output_time=ifft(I_output_freq);
Q_output_time=ifft(Q_output_freq);       

r=abs(I_output_time + i*Q_output_time);  
sys=10*log10(r);