The Research And Design Of UHF RFID Reader Module

RFID(Radio Frequency Identification) is an automatic identification technology, which is based on electromagnetic theory, antenna technology, radio technology, microwave technology and data encoding and decoding. The UHF RFID is widely used in our life because of its advantages of high transmission speed, long recognition distance and safe. It has become a hot topic between enterprises and research institutions. This paper has designed and researched of UHF RFID reader module.After analyzing the constitution of the UHF RFID system, we explain the role of each module in the system, and it is divided into two categories: inductive coupling and electromagnetic reflection coupling. The RFID has an external antenna, so we have given the concept of far-field and near-field region. UHF RFID hardware circuit is mainly divided into three parts: digital hardware circuit, RF hardware circuit and power conversion circuit. Digital circuit includes controller C8051F340, clock circuit, reset circuit and communication interface circuit. RF circuit includes RF chip AS3992, AS3992 power, crystal oscillator circuit, a loop filter, amplifier circuit and directional coupler circuit. Power conversion circuit includes the power conversion design. For the microstrip antenna, this design explains how it works from angles of radiation and radiation field. and show the design steps and parameters of microstrip antenna. The method is analysised, which makes the antenna working in the condition of circularly polarized. Finally, three nucrostrip antennas HFSS model and simulation diagram is shown. The research of UHF RFID radio channel is divided into two parts: multipath interference analysis, and maximum capacity. Multipath interference analysis the impact of multipath interference, mathematical expression of channel model and amplitude attenuation of Rician and Rayleigh channel. Maximum capacity of the channel mainly gives the maximum capacity formula and simulation diagram, which is based on the average power and water injection.This design of UHF RFID reader has the advantages of variety of communication interfaces, high read and write speed, long recognition distance. Three microstrip antenna to fully meet the requirements of the reader has a higher gain, wide bandwidth and low reflection coefficient. Calculated channel capacity and simulation approaches the true situation. The EPC code of tag is read successfully by the RFID system.