Design And Implementation Of RFID Reader In Coal Mine Safety Early Waring System

Radio frequency identification technology is a kind of wireless communicationtechnology. This technology is based on scattering technology in radar. The RF signals inspace coupling the non-contact way does not need to set up a corresponding mechanicalconnection between recognition system and specific goal. It not only can automaticallyrecognize multiple targets, but also can read and write related data. This technology canwork in harsh environments, and when works it does not need manual intervention.The reader which designed meets ISO/IEC18000protocol and the standard ofChinese ultra-high frequency. The paper’s hardware selects STM32processor and at thesame time designed SD card storage circuit, USB and RS232C interface, LCD displaycircuit. RF front-end circuit adopts AS3992chip, includes clock circuit power amplifiercircuit, low noise amplifier and voltage controlled oscillator circuit. This paper not onlywrites main program flow chart of control program, but also AS3992communicationprogram and communication protocol by C language.The antenna has a direct impact on the reader. Traditional antenna’s size is large,and recognition distance is short. The paper structs a fractal antenna which combinedthe fractal theory with ideas of design traditional microstrip antenna. The workingfrequency of the fractal antenna is capable of920MHz~925MHz; and return loss canreach-30dB when the center frequency is922MHz, and the bandwidth reaches15MHzwhen the antenna’s return loss under-10dB; and the antenna can achieves good circularpolarization performance VSWR<2; and the antenna gain is6.4385dB; and the sizewhich is60mm×60mm. It is better than the traditional90mm×90mm shrank by33%, the14.29%reduction ratio improved the traditional size70mm×70mm; and designof reader antenna theory to identify the maximum distance up to7.16meters.The reader has low power consumption, small size, accords with ISO/IEC18000-6Cprotocol requirements, and meets the relevant standard Chinese ultra-high frequencyband, stable and reliable performance, has market value.