f_s_k.m

一些非常有用的MATLAB源码,对于提高编程水平和学习通信理论知识还有帮助.

%--------------------------------------------------------------------
% F_S_K.m -----------------------------------------------------------
%
% Program for the simulation of deterministic frequency-selective
% mobile radio channels.
%
%--------------------------------------------------------------------
% [y_t,T,t_0]=F_S_K(x_t,f_max,m_s,T,t_0,q_l,...
%                       C1,F1,TH1,C2,F2,TH2,F01,F02,RHO,F_RHO,PLOT)
%--------------------------------------------------------------------
% Explanation of the input parameters:
%
% x_t: time-domain input signal of the channel simulator (sampled
%      with T_s=0.2E-6 s)
% f_max: maximum Doppler frequency
% m_s: sampling rate ratio
% T: contents of the delay elements of the time variant FIR filter
% t_0: offset in time
% q_l: q_l=tau_l/T_s+1
%--------------------------------------------------------------------
% The following matrices are generated in F_S_K_p.m:
% F1, F2: discrete Doppler frequencies
% C1, C2: Doppler coefficients
% TH1, TH2: Doppler phases
% F01, F02: frequency shift value of the Doppler PSD according to
%           Gauss I and Gauss II, respectively
% RHO: amplitude of the direct component
% F_RHO: Doppler frequency of the direct component
%--------------------------------------------------------------------
% PLOT: plot of the output signal of the channel, if PLOT==1 

function [y_t,T,t_0]=F_S_K(x_t,f_max,m_s,T,t_0,q_l,...
                     C1,F1,TH1,C2,F2,TH2,F01,F02,RHO,F_RHO,PLOT)

T_s=0.2E-6;

% Initialization:
mu_l=zeros(size(q_l));
y_t=zeros(size(x_t));

for n=0:length(x_t)-1,
    if rem(n/m_s,m_s)-fix(rem(n/m_s,m_s))==0,
       mu_l=sum((C1.*cos(2*pi*F1*f_max*(n*T_s+t_0)+TH1)).').*...
            exp(-j*2*pi*F01*f_max*(n*T_s+t_0))+j*...
            (sum((C2.*cos(2*pi*F2*f_max*(n*T_s+t_0)+TH2)).').*...
            exp(-j*2*pi*F02*f_max*(n*T_s+t_0)))+...
            RHO.*exp(j*2*pi*F_RHO*f_max*(n*T_s+t_0));
    end
    T(1)=x_t(n+1);
    y_t(n+1)=sum(mu_l.*T(q_l));
    T(2:length(T))=T(1:length(T)-1);
end

t_0=length(x_t)*T_s+t_0;

if PLOT==1,
   plot((0:length(y_t)-1)*T_s,20*log10(abs(y_t)),'g-')
end