모바일 RFID 리더 시스템 설계 및 제작

Abstract

In this thesis, the mobile RFID reader having simplified hardware is proposed, and the performance of the RFID reader is verified through measurement. In general, the activation power of tags is about -10 dBm, and the maximum tag recognition distance is considered about 1m for mobile RFID services. From this, the RF output power of the proposed RFID reader is determined to 20 dBm that is the minimum level required to provide application service properly. Lowering the output power enables to decrease the size and the number of the required electronic elements for proper design of the RFID reader. In designing the RFID reader, single chip RF transceiver, CC1020 manufactured by Chipcon AS., is used for reducing the size and for simplifying the design of hardware. However, a general-purpose RF transceiver can not meet the requirements in modulation scheme, data encoding method, and data transmission rate required to recognize the RFID tag data properly. These requirements are fulfilled through the implementation of the well-designed system firmware. To satisfy these requirements, the system firmware is designed as follows. First, in the modulation scheme, the system firmware of the RFID reader is designed to use ASK modulation scheme and to change the receiving frequency in confirmation process of the received signal. Second, in relation to the data encoding method, the PWM signals required to recognize the tag are generated using loop structure by the micro-controller, and those are transmitted through the transparent mode of RF transceiver. By using this process, the transmission of the pulses having proper width for recognizing the tag can be carried out. Last, the data transmission rate is determined somewhat slower than the value in the standard. The appropriateness of decided data transmission rate is verified through measurement. And the measurement on the overall characteristics of manufactured RFID reader such as the transmitting and receiving frequency characteristics, the timing characteristics of the pulse signals for tag recognition, the receiving characteristics of the tag response signal at the determined data transmission rate and the receiving characteristics of the tag response signal by distance is carried out. Through this process, the conformance to the EPC RFID standards is verified. Also, the comparison with commercial RFID readers is carried out. From the measurement results on the overall characteristics of the manufactured RFID reader, it conforms to EPC RFID standards. The manufactured mobile RFID reader has 11kbps minimum data transmission rate, and can recognize tags at a distance of 50cm maximum. The overall size of the manufactured RFID reader is 71mm × 55mm, that is the maximum 90%, minimum 14% reduced size compared with marketed product. The advantage of the proposed RFID reader is that the RFID application service network is established without additional communication hardware.