Test and Analysis of Passive UHF RFID Readability in Multipath Environments

In passive radio frequency identification (RFID) system, tag turns on when the received power is more than tag chip sensitivity. Therefore, sensitivity and the received power are determinant to affect passive RFID readability. The required power by tag depends on the chip manufacture, but the received power is affected by many factors besides of antenna and RF front end, especially at UHF band. In this paper, a test has been developed to show the readability of UHF RFID in indoor multipath environments. The read blind point and the fluctuation of read scope are observed. Then, based on the test scene, theoretical analysis of readability, which refers to many aspects, for example, multipath fading, frequency, tag position, antennas height, polarization scheme and reader receiver sensitivity and so on, is explored.