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Re: [Discuss-gnuradio] Re: RFID Capture

From: Marco Bottino
Subject: Re: [Discuss-gnuradio] Re: RFID Capture
Date: Tue, 24 Feb 2009 10:24:18 -0500
User-agent: Thunderbird (X11/20090105)

Hello All,
I'm trying to do more or less the same thing as Kevin but with two other
readers (a RFIdeas Playback and an OpenPCD) and other kind of cards (HID
IClass 2K and Mifare Classic 1K: both working at 13.56MHz).
I got an interesting signal just putting my loop antenna attached both
to the card and the reader: even if it is a bit weak, I can recognize
the tag reply.
(USRP 1, BaseRX with the usrp_rx_cfile.py  -f 13560833 -r B -d 16)
One of the problems I have is that I have to stay as much close as I can
to the card to be able to read its response (from more than 3 inches I
get an unreadable signal...), so I would like to ask Michael which kind
of antenna (and any external things) you used to be able to read the
signal from few feet away. Any suggestions will be very well appreciated.

Thank you very much,

Michael Buettner wrote:
> Are you using the ThingMagic in monostatic mode (one antenna that does RX and 
> TX)? If so, you probably won't be able to see the tag reply.  Further down 
> the receive path the ThingMagic has circuitry that removes the strong TX 
> signal leaving only the tag reply, but I assume you are tapped in before 
> that. You MIGHT have better luck if you use the reader in bistatic mode and 
> tap in at the receive antenna, particularly if you don't use the full 1W 
> output power. Another option would be to just put the USRP antenna near the 
> tag, and receive both reader and tag commands there. I have had pretty good 
> luck with that, and can decode tag responses from a few feet away.
> michael
> > Hello All,
> >  I am trying to capture the communications between a RFID reader and
> > an EPC Gen 2 tag (920 MHz).  I tapped directly into the antenna of a
> > Thinkmagic M5e RFID reader.  I turn it on and it starts reading the
> > tags.  When I look at the raw signal from the usrp or an Agilent
> > signal analyzer, I can clearly make out the reader-to-tag data bursts.
> >  But, I don't see the tag-to-reader bursts.  I know they should be
> > considerably smaller in amplitude, but all I see is noise.
> > Has anyone had any luck capturing this type of data?  Any suggestions
> > would be greatly appreciated.
> > Thanks in advance,
> > Kevin
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