tailieunhanh - Radio Frequency Identification Fundamentals and Applications, Design Methods and Solutions Part 5

Tham khảo tài liệu 'radio frequency identification fundamentals and applications, design methods and solutions part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 92 Radio Frequency Identification Fundamentals and Applications Design Methods and Solutions 25 A. Denoth The monopole-antenna a practical snow and soil wetness sensor IEEE Trans. Geoscience and Remote Sensing Vol. 35 Issue 5 pp. 1371 - 1375 Sept. 1997 26 L. Apekis C. Christodoulides P. Pissis Dielectric properties of paper as a function of moisture content Dielectric Materials Measurements and Applications 1988 Fifth Int. Conf on pp. 97 - 100 1988 6 Antennas of RFID Tags Ahmed M. A. Salama College of Electronics Engineering University of Mosul Iraq 1. Introduction Radio Frequency Identification RFID is a rapidly developing technology which uses RF signals for automatic identification of objects. RFID system generally consists of three components 1 A small electronic data carrying device called a transponder or tag that is attached to the item to be identified 2 A reader that communicates with the tag using radio frequency signals 3 A host data processing system that contains the information of the identified item and distributes the information between other remote data processing systems. A typical passive RFID tag consists of an antenna and RFID chip. RFID tags can be active with battery or passive without battery . In particular passive UHF 860 960 MHz tags represent a near optimal combination of cost and performance Hunt et al. 2007 . Generally omni directionality for the tag antenna is preferred to ensure the identification from all directions. The structure of the tag antenna should also be low cost small in size have good impedance matching and insensitive to the attached objects to keep performance consistent Curty et al. 2007 . A passive RFID system operates in the following way RFID reader transmits a modulated RF signal to the RFID tag consisting of an antenna and an integrated circuit chip. The chip receives power from the antenna and responds by varying its input impedance and thus modulating the backscattered signal. Modulation type often used in .