Hey Fernando,
not quite sure I get what you need; I'd say the Amplitude
Spectrum you'd be looking for is
![$$A_{|\cdot|}[f]=|X[f]| = \left\lvert\sum_{n=0}^{N-1}
x[n]\cdot e^{j2\pi \frac {nf}N}\right\rvert $$](pngy5Yk6S0UYI.png)
or, rather, the decibel representation of that. There's no way to
get a negative number out of the absolute of something – it's by
definition a positive real number.
Now, we could also use our freedoms to define our amplitude
spectrum to take the shape
![$$A_\text{signed} = s(X[f]) |X[f]|\text{ with }
s(X[f])=\begin{cases}1&\text{for } -\pi \le \angle X[f] <
\pi \\ 0 &\text{else.} \end{cases}$$](pngWBNDg4o8KK.png)
But: that's really only useful if you have phase-coherent
reception – as an analytic tool for an unsynchronized observation
of the spectrum, it doesn't help you much, since you have a random
due
to having random relative phase.
So, maybe it'd be a good idea to formulate what purpose you're
doing this for :) You can, indeed, tell 180° out-of-phase signals
apart by this, but I'd argue that being 180° out-of-phase, for the
most things I can think of, is only meaningful on one and the same
frequency – and hence, I'm not quite sure this is what you're
looking for!
Best regards,
Marcus
Hello.
Yes, with Time sink I can see the difference, but if the signal is compound of some other signals (for instance signal=1K/amplitude +1 +2K/amplitude -1 +3K/qamplitude +1 +4K/amplitude +1 ) i would like to see the 2k signal as -1 amplitude, but in the power spectrum it will appear as possitive and in the QT time sink it is very difficult to see the signal as it is a complex one.
regards
El 25/04/17 a las 10:57, Jinyang Lee escribió:
Hello Fernando,
I think the QT GUI time sink displays the relationship between time and amplitude. You can see the signal through it. But when I use the channel model block,the QT2 can see the signal which is zero.Enclose is running result with channel model and with channel model.
Regards,Lee
2017-04-25 15:45 GMT+08:00 Fernando <address@hidden>:
Hi.
Is there a way of visualizing ampitude spectrum (with + and - signals)
instead of power spectrum?
regards
_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
_______________________________________________ Discuss-gnuradio mailing list address@hidden https://lists.gnu.org/mailman/listinfo/discuss-gnuradio