Read Range And Selectivity; Antenna Allocation According To Tag Type - Kathrein LORA Anwendungshinweis

3. Read range and selectivity

The read range and selectivity are the most important properties of an RFID
application. The read range refers to the largest distance at which a tag can
be read and selectivity refers to the minimum distance required to clearly
differentiate between two transponders positioned next to each other.
The system properties depend largely on the type of transponder used. The UHF-
RFID tags can be divided into three main groups: The first group is made up of
small, loop tags (near-field tags) with an average diameter of 2 cm and which
mainly couple magnetically with the reader antenna. These transponders have
the smallest ranges, as the magnetic field falls extremely quickly with the distance
from the reader antenna. The second group includes the so-called hybrid tags,
which have a mixed shape somewhere between a loop tag and a dipole tag.
These tags can be activated by the reader antenna through the magnetic field,
the electric field or a combination of the two. The final group includes the far-
field tags, which couple mainly via the electrical field. These tags can achieve
ranges of over 10 m.
3.1

Antenna allocation according to tag type

The ULORA was developed to fulfil the most challenging demands with regard to
range and selectivity of the tags from all three groups. It is a universal antenna
for a wide variety of low range applications. With this antenna, extremely low
read ranges under 10 cm and high selectivity with far-field tags are possible.
It can also read near-field tag at distances of up to 3 cm. In order to significantly
increase the reading distance for near-field tags, the LORA was developed for
read ranges of 7 cm with conventional loop transponders. The figure under 3.1
shows the allocation of ULORA and LORA to the different tag types. It is evident
that the ULORA is suitable for all three groups, while the LORA is particularly
suited for use with loop transponders.
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