gmsk_mod.m

MSK的调制解调程序

function [gmsk_signal,GMSK_I,GMSK_Q]=GMSK_mod(fb,w,vstup,Bn)

% GMSK - gaussian minimum shift keiyng
% fn - nosna frekvencia
% fb - bitova rychlost v bit/s 
% SNR - poner signal-sum
% >> msk(500,3000,30);

M = 100;                          
tb = 1/fb;
krok = tb/M; 
N = size(vstup,1);	

for i=1:N;
    if vstup(i)==0
        r(i)=-1;
    else
        r(i)=1;
    end
end
r1 = r(1:2:N);
r2 = r(2:2:N);

t = -tb:krok:(1-krok)*tb;
for i = 1:2*M
    q(i) = 1.0602*quad8('puls',-tb,t(i),[],[],Bn,tb)/tb;  
end

for i = 1:N/2
    for j = (i-1)*200+1:(i-1)*200+200;
        phase1(j) = q(j-(i-1)*200)*r1(i);
        phase2(j) = q(j-(i-1)*200)*r2(i);
    end
end

% I a Q zlozky

for i = 1:M*N 
    GMSK_I(i) = cos(phase1(i)*pi-0.5*pi);
end
for i = M*N+1:M*N+M 
    GMSK_I(i) = 0.;
end
for i = 1:M 
    GMSK_Q(i) = 0.;
end
for i = M+1:M*N+M 
    GMSK_Q(i) = sin(phase2(i-100)*pi);
end

% scitanie I a Q - vysledny signal

t = krok*(-M:M*N-1);
gmsk_signal = GMSK_I.*cos(w*t)+GMSK_Q.*sin(w*t);
%s = I+Q;