RFID Capture

GNU Radio
1

(Sorry if this posts twice)

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

2

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 M.

3

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,
Kevin