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RE: [Discuss-gnuradio] RFID Capture

From: Paul Mathews
Subject: RE: [Discuss-gnuradio] RFID Capture
Date: Mon, 23 Feb 2009 10:43:33 -0800

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,

Yes, indeed, the backscatter signals from the RFID tags typically have quite
small amplitudes, and it may be difficult to trigger on them. Try bringing
the tags quite close to the reader and use various antenna alignments. Tag
signals will put small notches in the carrier envelope. You might have a
better chance of seeing them if you use a 3rd antenna for your receiver,
positioning the tag between the reader and your receiver antenna.
Paul Mathews

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