Summary
International Symposium on Antennas and Propagation
2008
Session Number:2SS01A
Session:
Number:2SS01A-6
Quasi Log-Periodic Antenna for Passive UHF RFID Tags
Heng-Tung Hsu, Cheng-Hung Chang,
pp.-
Publication Date:2008/10/27
Online ISSN:2188-5079
Summary:
Radio frequency identification (RFID) is a rapidly developing technology which widely adopted for various data collection applications such as transportation payments and retail item management. When RFID frequency rise into the UHF region, it is hard to design a tag antenna for passive UHF RFID applications because the passive tag ICs terminals is no longer 50 ohms or 75 ohms that has small resistance and large capacitive reactance, which makes it has high quality factor and not easy to achieve a wideband characteristic for the tag antenna. Some UHF RFID tag antennas have been published [1-3]. Quasi log-periodic antenna was first proposed by Hsu, et. al. [4]. This simple antenna structure basically consists of a regular center-fed half-wavelength dipole with two mutually-coupled stubs. The main advantage of the quasi log-periodic antenna is the ability to achieve relatively wide bandwidth with omni-directional radiation pattern and 2dBi gain. The excellent performance achieved through this simple structure has created itself great potential for applications in tag antennas of Radio Frequency Identification (RFID) systems. For the basic structure of the quasi log-periodic antenna, we added the quasi-lumped elements in parallel with tag ICs input to achieve a proper impedance match between the antenna and tag ICs. The antenna were designed for the RFID standard referred to as Class 1 Generation 2 ("Gen. 2"), with the frequency band 902-928 MHz.