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Re: [Discuss-gnuradio] RFID Capture

From: Kevin Rudd
Subject: Re: [Discuss-gnuradio] RFID Capture
Date: Tue, 24 Feb 2009 13:57:15 -0500

Thanks for all the advice.  After turning the power way down and
placing the tag within inches of the antenna, I can see the tag's
burts.  It makes me wonder how the reader can pull out the tag's
bursts in 'real world' conditions.  There is no processing gain to
pull it out of the noise.

Thanks again,

On Mon, Feb 23, 2009 at 1:43 PM, Paul Mathews <address@hidden> wrote:
> 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
> 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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