Design Of Antennas For RFID System

As an automatic identification technique without touching, radio-frequency identification (RFID) technology use radio waves carrying information stored about the identified object or commands to identify objects via space coupling, such as inductive coupling or electromagnetic wave propagation. Compared with other identification technologies, RFID technology used for identification has many advantages, of which the most potential one is the huge market for RFID system applications. Thanks to the rapid development of electronic techniques and manufacturing technology, the RFID applications based on the wireless and radar techniques emerge rapidly, which will be found very useful in many fields, such as goods stocking and distribution, supply chain, commerce and trade, manufacturing, identification, and security management. As a vital and integral part of RFID system, RFID antennas have received much attention, and their design is very urgent and significant. In fact, the development of RFID antenna is of theoretical significance and practical value for the RFID system.First, a brief introduction to the RFID technology is given, the operating principle of RFID system and related knowledge are described, and meanwhile the antenna in RFID system is analyzed and discussed. The author's contribution in this thesis include following aspects. First, the impedance chat of constant power transmission coefficient for matching between antenna and chip is draw, according to the impedance matching concepts, and a new modulated transmission RFID system in UHF band is designed for practical application and is also tested. Second, a compact antenna structure is proposed and designed for realizing dual circular polarization for RFID system. In order to meet the system requirements, some modifications are made to improve the performance. An antenna prototype is also fabricated and measured, and the measured results show that the antenna is suitable for implementing the circular polarization modulation in RFID system and that the design method is efficient. Third, a dual band antenna with RF performance suitable for microwave band RFID tag use at 2.45/5.8 GHz is designed and fabricated. The simulated and measured results show that the performance of the antenna meets the special system requirements. The antenna structure with low profile, low cost and small size is mechanically robust and easy to fabricate and integrate with the application-specific circuit. Finally, some problems facing in RFID system application are analyzed and discussed. Solutions are given, and relative calculations are also implemented.