The Design And Simulation Of 915mhz Rfid Tag

REID(Radio Frequency Identification)is a kind of non-contact and automatic identification communication technology which is realized by radio frequency communication technology.At present,high-frequency and low-frequency technology have been relatively mature in China,but in the field of ultra high frequency,the research work is still in the initial stage,especially for the tag of 915MHZ frequency band based on ISO18000-6 standard. Because 915MHZ frequency band is just in the public mobile communication band,moreover,the study and application are mature,it is deserved to study ISO 18000-6 standard.In this paper,the ISO18000-6 standard has been studied.Its 915MHZ RFID tags physical interface,protocols,commands,and mechanisms for conflict prevention are analyzed.According to the provisions of the standard, designs the structure of tag and the modules of system,and designs the circuits of antennas,radio frequency interfaces,as well as digital control module.The details of circuits of radio frequency interface and EDA simulation are primary contents,which mainly includes power supply circuit,reset circuit,clock extraction circuit,backscatter modulation circuit and demodulation circuit module.Digital control module is also an important component of tag.Here, tag of Type B is introduced,analyzes and designs the digital control part, mostly includes Manchester coding module,FM0 coding module,CRC data check module,state machine module,EEPROM module and conflict prevention algorithm.Furthermore,the system level simulation of 915MHZ RFID tags has been done by use of Matlab.Emissive circuits and receiving circuits have been simulated in time domain through the model which is constructed by SIMULINK communication simulated model library,then realizes the tag's simulation in frequency domain by M file programming.The integrality and veracity of system have been validated from the time domain and frequency domain.At the same time,the simulation shows intuitively the signals situation of system,which can be referenced by engineers.915MHZ RFID tag designed in this paper uses a circular microstrip antenna as radio frequency front-end antenna,which has preferable reactance characteristics and can be used by tags that have strict requirements on power cost and radiation.For the complex radio frequency interface circuits, corresponding modules should be adapted to realize these functions;In the digital control Circuits design,the simple,easy programming and less power cost circuits are being used.Additionally,the circuit principle diagrams are designed and simulated by an excellent EDA simulation tool called Multism, which displays clearly the signals of every parts of system and reduces effectively the overall system design risk.