Influence of detection zone length on space coverage in a far field UHF RFID system

Absolute coverage is ultimate requirement for many modern RFID systems. Limiting of detection zone and appropriate choice of tags are some of the crucial issues in creating of such system. In this paper we analyzed an RFID system with circularly polarized reader antenna, where objects (with tags) are collected through a gateway and can be detected in any position in detection zone, along the entering path. It is shown that coverage significantly improves by increasing the length of the detection zone if the tag's antenna is linearly polarized, while in case of circularly polarized tag's antenna this improvement is modest. Moreover, it is shown that for enough long entering paths a linearly polarized tag antenna can show better performance than a circularly polarized one. Circularly polarized tag's antenna is optimal choice if detecting zone is very narrow.