HF RFID Desktop Reader Antennas for Near-Field Application

NEAR-FIELD radio frequency identification (NF-RFID) systems are being widely used for item-level tagging in pharmaceutical and retailing industries [1]. Since in NF applications the tag detection has to be limited within an assigned confined volume close to the antenna surface, a proper reader antenna design is required. A number of solutions for NF UHF RFID reader antennas have been proposed.

Antennas for NF UHF RFID readers have to exhibit a field distribution as uniform as possible on the entire interrogation area (i.e., the reader antenna surface) to avoid missed readings (false negatives). The field distribution uniformity level can be evaluated by considering the probability density function (PDF) of the NPD. Specifically, by calculating the NPD at a set of test points on a geometrical surface at an assigned distance from the antenna surface, a PDF curve can be generated.

The power density (Euclidean norm of the real component of the Poynting vector) has been proposed as a metric to numerically assess the performance of NF UHF RFID antennas. A proper normalization factor has been included to allow for the performance comparison among reader antennas with different size. The spatial decay rate of the normalized power density gives information on the expected behavior of the reading performance versus the distance from the antenna surface. Moreover, its probability density function is suitable to qualitatively estimate the probability of missed readings related to low-field regions on the reader antenna surface. Numerical results have been shown for three antennas presented in the open literature for near-field UHF-RFID applications, as well as for a standard

resonant patch antenna.

UHF RFID Desktop Reader/Writer

Tags : UHF RFID readers UHF RFID Desktop Reader UHF RFID antennas

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