Meander-Line UHF RFID Tag Antenna with Semi-Circular Structure

Recently, the demand of the Radio Frequency Identification (RFID) system is increased for using in many applications such as personal access control, logistics, industrial process, product management, including identifying people, animals and products. The frequency band of the RFID system can be divided into four bands such as low frequency (125-134.2 kHz), high frequency (13.56 MHz), ultra high frequency (433, 860-960 MHz) and microwave frequency (2.45, 5 GHz). Each frequency band is used in different applications [1]. The main application of ultra-high frequency (UHF) RFID is used in the process of logistics, product and commercial managements. However, the standard of the UHF RFID in each country is different. In Thailand, the allocated frequency of the UHF RFID is 920-925 MHz [2]. This paper presents the RFID tag antenna design for the standard of UHF RFID in Thailand. An important requirement for the tag antenna design is that the impedance of the tag antenna must be conjugately matched with the impedance of the IC chip for the maximum power transfer from the tag antenna to the IC chip [3]. The proposed size of the antenna is relatively small (0.10 0   0  0  0.25 ), where is wavelength in free-space of 922.5 MHz. It is found that the tag antenna possesses good performance for using in UHF RFID systems.