Help me with mixing the Tx and Rx signal then LPF in Matlab

[gaboor]

Hi,

Iam trying to do some analysis for a redar system that uses Linear Chirp modulation. I have a problem mixing the Tx and Rx signal then LPF. RX is a delayed version of the Tx. Normally after mixing (muliplying Tx and Rx) i dont get the low freq part!!!

I tried Matlab Help but i cannot get it!

Any help Please?

 

[ahmad_abdulghany]

Re: Urgent: Matlab Help

Hi,

Iam trying to do some analysis for a redar system that uses Linear Chirp modulation. I have a problem mixing the Tx and Rx signal then LPF. RX is a delayed version of the Tx. Normally after mixing (muliplying Tx and Rx) i dont get the low freq part!!!

I tried Matlab Help but i cannot get it!

Any help Please?

How did you multiplied the two signals? are they sinosoidal functions? If so, you should obtain the low freq. component of the output of the mixer (multiplier).

Try it again, it may work,
Best Regards,
Ahmad,

 

[gaboor]

Re: Urgent: Matlab Help

the signal are Chirp

here is the code

fsample=10000;
frmsz=512;
t = (1:frmsz)/fsample;
f = (1:frmsz/2)*fsample/frmsz;

y = chirp(t,500,frmsz/fsample,1500,'li');
figure
plot (t,y),
title('Transmitted signal')
xlabel('Time (seconds)')

x = chirp(t,500,frmsz/fsample,1500,'li',-240);
figure
plot (t,x);
title('Received signal')
xlabel('Time (seconds)')

z=x.*y;

Z=abs(fft(z));
figure
plot(f,Z(1:frmsz/2))

After i LPF the mixed signal (z) i exoect to get a sinosidal signal in the time domain!

Any idea?