Affiliations: [a] Digital Communications Signal Processing (DCSP)
Research Laboratory, Faculty of Electrical and Computer Engineering, Shahid
Rajaee Teacher Training University (SRTTU), Lavizan, 16788-15811, Tehran,
Iran. Tel.: +98 21 2297 0006; Fax: +98 21 2297 0006; E-mail:
sh_shirvani@srttu.edu
Abstract: The main objective of this paper is to model environmental effects
on the read range of radio frequency identification (RFID) system. In order to
evaluate the performance of an RFID system in real applications, electric and
magnetic radiated fields (E or H) of a circular loop antenna should be derived.
In this investigation, three cases are considered, free space model, the case
that there is a perfect parallel or non-parallel surface, and finally the
general model considering non-parallel non-perfect conductive/dielectric
surface. In general model, besides the method of images, a new approach is
proposed which model non-parallel main and image CLAs as two equivalent
vertical and horizontal loops. According to this model, the radiated fields and
also induced voltage are functions of the current intensity, wavenumber,
reflection coefficient of the surface, both angle and the distance between
antenna and surface, and the distance between the RFID tag and reader. To
compare the analytical values extracted from E and B formulas of proposed model
and associated results derived from computational methods, MATLAB and FEKO
outputs are compared in the same conditions. Using this new proposed model, the performance of an RFID system
operating in metal environment and also effective read range can be evaluated.
It is also able to show the environmental effects on radiated fields of reader
as well as tag's antenna. In addition, the interference effect of different
RFIDs can be easily modeled by these new formulas.
