Summary
International Symposium on Antennas and Propagation
2008
Session Number:2SS01A
Session:
Number:2SS01A-4
Parametric Study of the Novel UHF RFID Dual-loop Antenna
Milan Svanda, Milan Polivka,
pp.-
Publication Date:2008/10/27
Online ISSN:2188-5079
Summary:
Currently, UHF RFID systems are increasingly apllied in many areas. They are operated with a decent reliability in free space or are placed on paper-like boxes [1]. The main advantage of this frequency band is represented by a relatively low free-space loss, which enables to read a range of several meters. However, problems arise in case that a TAG antenna is placed in the close vicinity of lossy dielectrics or metal objects. The first case corresponds to the identification of persons and the second one corresponds to e.g. the identification of metallic containers. UHF RFID systems use often shorted dipole type antenna. Unfortunately, the location of this antenna type in the close vicinity of lossy objects causes a substantial detuning of its resonant frequency and, at the same time, a considerable fall in antenna efficiency. This type of antenna is not ideal for the abovementioned applications. An antenna with a metallic ground plane (serving as a protective shielding) seems to be the best solution of the issues described above. The metallic ground plane increases the front-to-back ratio of the antenna, hence it reduces the influence of an object to be identified to the antenna parameters. However, as the UHF RFID system operates within the frequency range of 860-930 MHz, the TAG antenna resonant size has to correspond to the half-wavelength, which is of about 170 mm at frequency 869 MHz. Such size is inacceptable for TAG antennas - thus they are highly inconvenient for the purposes of identification of persons. The novel electrically small flatten dual-loop antenna, which is discussed in detail in this paper, represents a promising solution of above-mentioned problems. The antenna has been manufactured and measured. Finally, a parametric study of the antenna parameters change has been undertaken.