Electromagnetic Performance Evaluation of UHF RFID Tags With Power Discretization Error Cancellation

The rigorous electromagnetic characterization of passive UHF radio frequency identification (RFID) tags is a challenging task. Among various solutions, in a previous work, an automatic tool for the over-the-air evaluation of significant RFID tag metrics has been presented. Once the distance is fixed, the system, based on the estimation of the minimum power emitted by the off-the-shelf interrogating reader capable to energize the tag under test, exhibits an accuracy that, although adequate, is affected by the minimum power step at the reader side. In this communication, an evolution of a new platform whose working principle has already been introduced by the same authors is presented. It is based on an analytical model opportunely derived to overcome this limit while preserving flexibility and cost-effectiveness. The platform can automatically vary with continuity the interrogation distance-which becomes a new degree of freedom-and it is able to estimate the couple power distance for each frequency, which practically annuls the estimation error due to the power discretization. Moreover, the enhanced system now allows for a pretest phase that is useful to verify whether or not the implemented analytical model is valid in the specific environment, even if not electromagnetically anechoic.