Reseach On The Application And Design Method Of RFID Near-field Antenna

In recent years, RFID(Radio Frequency Identification) systems have been applied in many areas such as traffic, logistics and goods flow systems, industrial manufacture, equipment monitoring, service industry and etc. A RFID system consists of three parts, namely tags, an application system and a reader. Relying on in which radiation region of the reader antenna the tag is activated, RFID systems can be divided into far-field RFID systems and near-field RFID systems. Given the characteristics of ILT(Item Level Tagging) and higher data communication and storage, near-filed UHF RFID systems receive more and more attentions. Thus, more importance is attached to the research on the design of the reader near-field antenna applied in the near-filed UHF RFID systems. For the reason that there is no regular pattern in the near-field radiation region of the antenna, there is no effective design theory support to the near-field antenna. Therefore, research on the method of the near-filed antenna’s design and test has become a most important study topic.In this thesis, an optimum design method of the near-field antenna is put forward, on the basis of near-field coupling theory and microstrip antenna’s cavity model(CM) method. And the designed antenna has applied into the cabinet equipment monitoring system. The major work of this thesis can be summarized as follows:(1) Based on the microstrip antenna’s cavity model method, an objective function is proposed with the field distribution of the microstrip antenna’s near-field radiation region in Mode TM as the major parameter. By adjusting the geometry of the antenna, the objective function can reach to the optimal solution.(2) The simulated results of the return loss and the field distribution of the antenna’s near-field radiation region is achieved by the software HFSS, with the antenna in free space as well as in the environment of the cabinet.(3) A measuring system aimed at the field distribution of the antenna’s near-field radiation region under the environment of the cabinet is established. And the field distribution of single antenna’s near-field radiation region has been tested.(4) A design scheme of the antenna system aiming at covering the cabinet monitoring plane is put forward, with a time division system as the connection of the RFID reader and the eight near-field antennas.The antenna has been fabricated and tested. Under the environment of the cabinet, the return loss is less than-10 d B covering the frequency band from 918 MHz to 926 MHz and the antenna is resonating at the frequency of 922 MHz. What’s more, the field distribution of single antenna’s near-field radiation region can cover a region of 500mm×300mm in the cabinet monitoring plane, on the basis of which the antenna system’s design scheme is determined. Ultimately, a summary of the entire thesis is given, as well as the prospect of further study in the future.