Avery Dennison RFID - Manual (Page 30)

HowToRFID
Revision: 13 Date: 31 August 2009
Page 30 of 53
4.2 Inlay qualification
4.2.1 The inlay qualification process
Using only the built-in functionality of the RFID enabled printer it’s more or less difficult to find out the best settings
for the RFID parameters to process a given RFID label in a safe manner.
Furthermore some of the very important parameters are already fixed (unchangeable) if a converted RFID label is
used. That’s mainly the placement of the inlay inside the label:
a) distance from top of label in feed direction,
b) placement from the left edge of the label,
c) the orientation of the inlay (typical forms: chip first or chip trailing), and
d) the distance (pitch) between two subsequent inlays (in subsequent labels).
All of those parameters have significant influence on the performance and throughput of the encoding (and printing)
process in the printer.
To get optimum performance and throughput it’s necessary to have the inlay placed in a printer- and inlay specific
optimum position in the label. This assures well coupling between the printers antenna and the (and only that) inlay
“near” the printers antenna.
On the other side it’s important to have the right minimum pitch (distance) between to subsequent inlays to avoid
the unwanted writing (and reading) to more than one inlay at once. These unwanted side-effects are also called
“crosstalk” or “adjacency” effects.
Please note: due to the EPC being “the” unique identifier of a EPC Gen 2 transponder, it’s not detectable whether
only one or multiple transponders have been “hit” by a write operation during the encoding. This would first be
possible after a unique EPC was written to each transponder – and what a bad luck – mostly the first and only
operation to be done is to write a unique EPC into the transponder.
So the only way to ensure individual programming of the transponders with a unique EPC is, to make sure it’s only
one transponder in coupling with the printer’s antenna. This can be attained by
a) using an antenna in the printer with a small “beam width” (restricted by physical limits),
b) using as less RF transmit (output) power as possible (but still enough to turn the transponder on),
c) use metal parts inside the printers paper path as shielding,
d) use a distance (pitch) between two inlays which avoids having two inlays at the same time in the RF field of
the printers antenna, and which additionally avoids energy transmission between subsequent inlays.
Another parameter having influence on the performance of an inlay is the RF regulatory region where the printer
shall operate. This is due to
a) varying sensitivity of the inlay itself for the different frequencies used,
b) different RFID reader modules used in the printer for the different regulatory regions (EU/ETSI, US/FCC,
Korea) => different RF output/transmit power and receive sensitivity
c) frequency depending RF field characteristics of the printers antenna
Because there are so many system- and transponder (inlay) specific parameters, it’s necessary to test a selected
transponder (inlay) in the target printer before designing and producing a label for a specific application.
To avoid this high burden for system setup, Avery Dennison makes the test of several well known transponders
(inlays) in advance. The results of the tests – the recommended parameters for each transponder and printer – are
published in several ways. This all together is called the “inlay qualification process”.