Research And Design Of The Long Range RFID Reader System

Radio Frequency Identification (RFID) is one technology of Automatic Identification, which is used with the coupling of radio magnetic filed to realize contactless communication and identify the items.The paper has designed one RFID Reader for Tag-it tag and Mifare tag. The design of hardware include designs of RF ASIC module, MCU circuits, serial interefaces, RF power amplifier (PA), RF signal processing circuit and so on. The designs of RF PA and RF ASIC module are main parts. Because the PA is a linear power amplifier, i.e. AB type, it was able to amplify two different type of modulation ASK and FSK signals. The match circuits were used to match the input circuits (the output of RF ASIC module) and output circuits (the input of the antenna), to achieve the high stability of the RF PA. Since the signal received by the antenna was too small to be demodulated by the circuits of the ASIC, a diode detector was to demodulate the signal modulated by subcarrier.Then it was amplified and a remodulation with the carrier of 13.56MHz. At last, when the signal satisfys the input signal's strength and modulation depth of the RF ASIC.Both Tag-it tag and Mifare tag are passive tags. The reader realized the function of using one antenna to send and receive RF signals. That is the antenna of reader has to send/receive RF signals, and has to power the passive tags too. The software of the reader was based on embedded C languge. It implemented the communications of reader to backend database and reader to tags. The RFID anticollosion module was base on binary-tree search algorithm.