Summary
International Symposium on Antennas and Propagation
2008
Session Number:2SS01A
Session:
Number:2SS01A-5
A Dead Spot Analysis in Simultaneous Read of Multiple RFID Tags
Peng Wang, Sho Yamada, Shigeki Obote, Kenichi Kagoshima, Kenji Araki,
pp.-
Publication Date:2008/10/27
Online ISSN:2188-5079
Summary:
RFID (Radio Frequency Identification) systems consist of RFID tags and readers and this technology uses the electromagnetic radiation to provide contact-less recognition. It has the unique advantage that it can provide simultaneous read of multiple tags, but we have observed that either a maximum read range or recognition rate becomes low during this operation. Especially, we are here concerned with the mechanism of the low recognition rate called dead spot and studied this by the experiment and simulation. A dead-spot of RFID tag means that a recognition rate is quite low within the maximum read range. In the case of reading only one tag, the mechanisms of the dead spot are well studied by the previous works. In one study, it is reported that the recognition error may occur when tags are close to the reader antenna which consists of four patch antennas[1]. In another work, it is also reported that the recognition error is caused by impedance miss-match between a tag antenna and a load at a certain distance, because a input impedance of a load depends on the power of the incident wave [2],[3]. However, there is no previous works on the dead spots analysis in the case of the simultaneous read of multiple tags so far. In this paper, we first conducted experiments on the simultaneous read of multiple tags using 2.45GHz band RFID tags and present the phenomenon of the half-wavelength period dead spots. And then, we next analyzed the mechanism of the dead spot by the method of moment simulation.