When we multiply two complex signals in GNU Radio companion and see the

result using WX FFT block then there is no frequency difference

component(f1-f2) but only the addition component(f1+f2)…why is that??

On 08.05.2014 08:59, ali hanif wrote:

When we multiply two complex signals in GNU Radio companion and see the

result using WX FFT block then there is no frequency difference

component(f1-f2) but only the addition component(f1+f2)…why is that??

That is actually the mathematically correct thing.

M

Can you plz explain Martin or give me a link atleast…thnx in advance

I think you are confused because you’re doing the math on paper with

real sin/cos functions. The complex signal sources produce complex

oscillations ($s_f(t)=e^{j2\pi f t}$), which do not have symmetrical

spectrum.

Do the math with the exponential function; it get’s easier than what you

have to do to prove the real intermodulation signals, and you clearly

see that $s_a s_b = s_{a+b}$.

Greetings,

Marcus