Re: [Discuss-gnuradio] Re: Complex samples format with ASK modulation

[Marco Bottino]

Hello CJay,

thank you for answering me!

Selon "C.cc Jay" <address@hidden>:

> Hello Marco
>
> I not familiar with RFID ASK10% or ASK100%.
>
> (1)
> I use usrp -> sinkfft. I can see the wave and tune the target frequency
> to 13.56MHz

What do you mean with tune the target frequency? Isn't the carrier always at
13.56MHz?

>
> However, I don't understand the question "why USRP outputs I/Q samples?"
> I have to reading more knowledge about communication theory.

I asked that because in my opinion I should not need any kind of phase
information because of the ASK modulation used that is an amplitude modulation.
So I don't know if I have simply to throw away the Q samples or not...

>
> (2) You want to plot in the time domain
> When I got RFID signal, I will do demodulation and get the information
> carried by the phase. I still trying.

I'm sorry for my ignorance but which is the information carried by the phase?
With "demodulation" what do you exactly mean? USRP isn't able to sample
directly at the RFID's frequency?

Finally, reading the ISO standards it seems that is always used the ASK
modulation... isn't it?

Thank you,

Marco

>
> CJay
>
> Marco Bottino wrote:
> > hello everybody,
> >
> > I am using the USRP with LFRX daughterboard to catch an RFID signal ASK
> > modulated (frequency 13.56MHz, decimation factor 16).
> > I really need an help because I don't understand very well the meaning
> > of the
> > outputs of my USRP: if the information related to the ASK is only the
> > amplitude, so  why USRP outputs I/Q samples?
> > Which is the meaning of the Q samples? Which is the information carried
> > by the
> > phase (that should not be important in ASK modulation)?
> > If I want to plot in the time domain the samples got, which kind of
> > operation is
> > necessary (given that I would compare my result with the
> > usrp_oscope.py)?
> >
> > Any kind of help will be really well appreciated.
> > Thank you,
> >
> > Marco
>
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