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Discussion Groups | Matlab DSP | non-coherent FSK demodulation using quadrature receivers

Technical discussion about Matlab and issues related to Digital Signal Processing.

  

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non-coherent FSK demodulation using quadrature receivers - Louis Angeles - Apr 14 21:39:00 2003



Hello, I've been working on an FSK non-coherent demodulation using a quadrature
receiver. I was actually getting some ambiguous results maybe you guys can
check it out. Anyway, here's my code %%%%%%%%%%%%%%%%%%%%%% demodulation
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% N = 100; % number of samples %% correlation
process %% % at higher freq. 3000 Hz
u1 = cos(2*pi*(3000)*t);
v1 = sin(2*pi*(3000)*t); % at lower freq. 2000 Hz
u2 = cos(2*pi*(2000)*t);
v2 = sin(2*pi*(2000)*t); for i=1:N,
r(i)=filt(i);
echo off;
end;
r1c(1)=r(1)*u1(1);
r1s(1)=r(1)*v1(1);
r2c(1)=r(1)*u2(1);
r2s(1)=r(1)*v2(1); % sum from 0 to N
for k=2:N,
r1c(k)=r1c(k-1)+r(k)*u1(k);
r1s(k)=r1s(k-1)+r(k)*v1(k);
r2c(k)=r2c(k-1)+r(k)*u2(k);
r2s(k)=r2s(k-1)+r(k)*v2(k);
echo off;
end; %% squaring and decision%%for k=1:N,
r1(k)=r1c(k)^2+r1s(k)^2;
r2(k)=r2c(k)^2+r2s(k)^2;
z(k)=r1(k)-r2(k);
if (z(k)<=0)
desi(k)=0;
else
desi(k)=1;
end;
echo off;
end;

Louis Angeles
BS Electrical Engineering
George Mason University




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