Water and metal objects are the most known factors that can decrease the performance of air interface Ultra High Frequency (UHF) communication between RFID passive tags and readers. Depending on RFID applications, several options to alleviate the material effect include the use of active tags, additional tag spacer or insert material, and specific tag or antenna design.

Two other factors that can also influence the performance of UHF RFID applications, yet less known, are mobility and tagging position. These two factors can be very significant in several applications, such as RFID vehicle and conveyor belt tracking systems.

Mobility is a critical factor for RFID tagged objects or readers that are moving or mobile. Depending on the configuration of a particular RFID system and environment, a significant change in mobility path (direction) and also speed (velocity) within a specified time can influence the successful identification rate of RFID tags.

Tagging position, on the other hand, is related to the position where RFID tags are embedded, attached or injected (in the case of animal or human tagging). In many cases, optimum power from RFID reader is not required to operate passive tags.

However, in cases where the Effective Radiated Power (ERP) level and distance between reader and tags are fixed, such as in manufacturing setting, it is important to know the location in a tagged object where a passive tag can operate optimally. Such location is defined as R-Spot or Resonance Spot.

R-Spot is a location in a tagged object where a passive tag can operate optimally within specified Effective Radiated Power (ERP) level and certain distance from a reader.

During RFID tagging, R-Spots are usually the reference tagging locations where the identification of tags will result in optimum performance.

In some cases, such as pallet and case tagging with different contents and materials, R-Spots are likely to be variably diverse. Such cases may introduce the difficulty in automation, because a fixed tagging location on all tagged objects may become a requirement to achieve an efficient automation. This situation introduces the importance of L-Spot or Live Spot, which is the location in a tagged object where a passive tag can still obtain power from a reader to operate within specified ERP level and certain distance from a reader.

L-Spot is the location in a tagged object where a passive tag can still obtain power from a reader to operate within specified ERP level and certain distance from a reader.

L-Spot includes R-Spots as well, but L-Spot does not always guarantee that the tagging position will result in optimum performance.

The opposite of L-Spot is D-Spot or Dead Spot, where tags can still receive power from a reader, but the obtained power is insufficient to operate tags within specified ERP level and certain distance from a reader, resulting in identification failures.

D-Spot is the location in a tagged object where passive tags can still obtain the power from a reader, but the obtained power is insufficient to operate tags within specified ERP level and certain distance from a reader.

There are still many areas in RFID tagging that are yet to be explored. This introduction to RFID tagging has shown that there is still room for improvement, while the art and science of RFID tagging advances along with the increasing adoption of RFID technology in diverse applications.


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Labels: antenna, d-spot, erp, l-spot, mobile, r-spot, reader, rfid, tag, technology, tracking

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