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G. Lasser, R. Langwieser, A.L. Scholtz:
"Broadband Suppression Properties of Active Leaking Carrier Cancellers";
Talk: 2009 IEEE International Conference on RFID, Orlando, USA; 04-27-2009 - 04-28-2009; in: "IEEE RFID 2009, 2009 IEEE International Conference on RFID", IEEE Catalog Number: CFP09RFI (2009), ISBN: 978-1-4244-3338-4; 5 pages.

In passive UHF RFID systems backscattering is
used for tag to reader communication. This technique relies
on a continuous wave signal being transmitted by the reader
during the tag´s data transfer. In order to separate transmission
and reception paths circulators, directional couplers or disjoint
transmit and receive antennas can be used. Perfect isolation is
not achievable with any of those approaches. So a leaking carrier
is present at the receiver in any case. It is possible to reduce the
interference from this signal by some kind of leaking carrier
cancellation. Such a cancellation prevents receiver blocking and
reduces the baseband hardware´s requirements, depending on the
receiver concept. Usually, the narrowband properties of carrier
cancellers are studied. This is only sufficient for conventional
RFID systems, if the transmitter noise can be neglected. Broadband
RFID systems, as recently discussed in literature, also
require broadband leaking carrier cancellers. In this paper the
broadband suppression properties of carrier cancellers are first
investigated theoretically. Further a hardware implementation is
presented and characterized. Finally, measurement results are
compared to the theoretical findings.

RFID; Active Carrier Cancellation; Isolation; UHF; Broadband

http://publik.tuwien.ac.at/files/PubDat_175359.pdf