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

[C.cc Jay]

Hello
(1) I mean "usrp.tune", use the instruction i can set my target 
frequency at 13.56MHz.

Now, I know you mean Usrp output I/Q samples. And you want to use one of 
them (I or Q sample).
My answer is NO, because I/Q sample you can see it like SIN and COS 
signal. So need both I/Q to demodulate signal. (If I am wrong, please 
tell me.)

The detail in book is very diffcult to me. I don't know how to explain.
Maybe someone can help me to explain it.

(2)
Sorry for my misunderstand before.
Use fft_sink, you can see usrp get the target frequency signal.
for example, my target is 13.56MHz. When my RFID device near USRP, I 
will see a wavefrom raise in 13.56MHz.


(3) In ISO/IEC 14443A
PCD to PICC using ASK100%, PICC to PCD using different modulation (OOK).
I just got draft spec. I need more study to understand the spec.

(4) My question to RFID spec. Do you know, what is Pause_A?

CJay

Marco Bottino wrote:
> Hello CJay,
>> (1)
> 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

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