The tag should be correctly oriented on a polystyrene
stand so that there is maximum coupling between the tag antenna and the reader antenna.
The reader output can be monitored while the tag is moved away from the reader antenna
to obtain the read range. However, it may be more practical to conduct the read range
Far-Field Tag Antenna Design Methodology 77
measurement in an environment suitable to that in which the tag is to be deployed as it
would give a more useful indication of the performance of the tag with respect to the
application.
The following section considers identifying necessary tag antenna design requirements
for a given application. Such identi?¬?cation should be undertaken before embarking on the
antenna design process. Identifying requirements will help the translation of application
requirements to design requirements for an RF engineer allocated to the task of designing
a tag antenna.
4.4 Label Antenna Design Methodology
4.4.1 Design Requirements
Table 4.4 provides a necessary set of considerations that should be deliberated upon to
identify design requirements before embarking on the tag antenna design process.
4.4.2 Design Methodology
Generally, RFID label size requirements are restricted by costs and practical aspects that
depend on the application and the frequency of operation. Most practical tag antennas for
UHF operation are physically small and hence tend to have a gain of around 1.
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