Strong Metal Environment Application Rfid Near-field Antenna Design And Research

RFID (Radio Frequency Identification) is an automatic wireless data collection technology with a long history. It has been used in many areas such as traffic, logistics and goods flow systems, manufacturing companies, equipment monitoring and services industry currently. RFID systems constitutes of three parts which are Readers (with antenna), Data Processor and Tags. According to the distance between the tags and the antenna of the Reader, the RFID systems can be divided into far-field RFID systems and near-field RFID systems. Near-field UHF RFID receives more and more attention as a possible solution for item level tagging (ILT) and high speed data transfer characteristics in pharmaceutical retailing industry now. For the reason that the fields nearby the near-field antenna are not angular as the pattern of the far-field antenna, what’s more the environments the near-field antennas work in are complex and affect the character of the antennas, so there is not a specific way to design a near-field antenna as the far-field antenna. Therefore the study of the near-field UHF RFID antenna, the way to design a near-field antenna working in the complex metal environment is a worthy research topic.In this thesis, a method of designing a near-field antenna based on the near-field coupling and the near-field to far-field transformation theory is put forward. With the method a near-field UHF RFID antenna fixed in the demanded way and used to monitor the equipments in cabinets was designed and tested. The main contribution of this paper can be summarized as follows:1. The method that the near field is converted to far field pattern is proposed based on the near-field to far-field transformation theory.2. Three antennas which are respectively two elements, three elements and four elements series feed microstrip antennas are designed with the method mentioned in the paper, which are simulated with the software HFSS and fabricated and tested.3. The affect the metal cabinets make on the antennas is simulated under the condition that the antenna model is created nearby a cabinet model. The performance of the antenna under the cabinet and in the free space is compared and analyzed. 4. According to the components of a RFID system, a simple near-field measurement system for near field RFID is set up, and which is used to test the antennas mentioned in the paper with a special tag as standard tag.5. The whole antenna the near field of which can cover the whole front face of a cabinet is designed with the two elements series feed microstrip antenna mentioned above.