© STid 2014 – No unauthorised reproduction | Introduction
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NA102A03_EN
Vehicle identification: TeleTag UHF
Introduction
The purpose of this document is to describe the approach to be used when developing a vehicle
identification project using TeleTag® technology, to ensure optimal outcomes for the required
configuration and installation conditions.
General principles of UHF technology
Operating principle
TeleTag® uses “passive” UHF (Ultra-High Frequency) technology, which means that the chip does not
require a battery to operate, because its power is supplied by the reader. In Europe, the frequency used
for this technology is 866 MHz (915 MHz in the USA).
This passive UHF technology can therefore be used to read data from an electronic tag with no integrated
power supply within a range of several metres.
Uses and limitations, environmental effects, useful information
Various laws of physics apply to this technology and can influence the way it operates. The major factors
to bear in mind are as follows:
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The materials the tag is used on or behind will influence reader performance (range and speed). A
tag should be matched to its environment to give the best possible results.
o
The same tag will operate very differently on metal or behind glass (windscreen).
o
At this frequency, radio waves do not travel well through liquids. A human body between
the reader/antenna and the tag itself could obstruct tag reading.
-
Radiofrequency identification does not work through metal.
o
Typical example: heat-reflective (or climate comfort) windscreens on modern vehicles
have a metallic film that blocks radio waves. Any tag that is behind this metallic screen
would not be read. However, these windscreens have non-treated areas that allow the
radio waves through.
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Radio waves emitted by the reader and the tag can bounce off obstacles and be diverted. The
presence of obstacles in the field can influence the results.
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UHF technology can be directional. Some antenna has a fairly directional “reading field”, rather
like the area lit up by a spotlight. The location of antenna will therefore need to be planned on
the basis their reading zone, depending on their characteristics.
-
A UHF tag may have a specific orientation, related to the polarisation of its antenna. A “linear” tag
will be orientation-sensitive and will not read as well horizontally as it does vertically.
