Re: [Discuss-gnuradio] I/Q samples and Analytic Signals

[Lucas Ingles]

Thanks very much for the help!

I obtained the book (fifth edition) and already read whole section 2.1 (Band pass and Low pass Signals).

That was exactly what I was looking for.

I have one more doubt. Figure 2.1-6 in page 25 shows a real demodulator (I attached the figure here).

This is not the same block diagram of the demodulador that we have inside Elonics E4000 Tuner (zero-IF demodulador).

We don't have a Hilbert transformer inside the zero-IF demodulator. We have just two paths, one multiplying by cos() and the other by sin().

Perhaps the Hilbert transform is implemented by handling the I and Q components as a complex number I+jQ inside GNU Radio?

Can someone please explain to me how the zero-IF demodulator is related to the real demodulator shown in the book?

Thanks very much again,

Lucas Lorenzi Ingles

2013/9/30 Aditya Dhananjay <address@hidden>

Perhaps, Chapter 2 of "Digital Communications" by John Proakis?

best,

aditya

On Mon, Sep 30, 2013 at 10:26 AM, Lucas Ingles <address@hidden> wrote:

Hello to all,

I am using GNU Radio to study digital communications systems.

I have been working on the basic FM receiver with RTL-SDR for a while.

I was trying to find out what is the theory behind the complex I/Q samples.

What I discovered is that I/Q samples are first related  to analytic signals (the pre envelope) and then to the complex envelope of the signal (the complex signal in base band).

In fact, what RTL-SDR outputs to the flow graph is the complex base band signal, in other words, the signal translated to base band with just the positive or negative portion of the spectrum.

Please, can someone with more experience confirm to me if I am correct?

Can someone please recommend me some reference books about the theory of I/Q samples?

Thanks very much in advance,

Lucas Lorenzi Ingles

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