Radio Frequency Identification is a wireless technology that is going to play a very important role as auto-identification solution for many application scenarios, where item-level traceability and high performance are crucial. Currently, some guidelines suggest the use of passive Ultra High Frequency tags for this kind of tracing system. In particular, Near Field UHF tags have also been suggested to face critical conditions such as the presence of liquids. Unfortunately, not all the requirements that a tag should satisfy in the different steps of the supply chain, can be met by general-purpose commercial tags in UHF band, both Near Field and Far Field. This is due to the effect on the performance of the presence of metals and liquids, as well as to the very stressful conditions such as high scanning speed, possible misalignment between tag and reader antennas, and multiple reading of tags. In this paper, we are presenting the main features that a far field UHF tag should own in order to work properly in the whole supply chain. A tag satisfying all the individuated requirements has been also realized and tested to trace some critical pharmaceutical products, containing metals and liquids, and has been compared with some commercial UHF tags, both Near Field and Far Field. The very impressive results clearly demonstrate that well-designed ad hoc Far Field UHF tags effectively improve the performance of any item-level tracing system.
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