A Design And Implementation On Rfid System For Long Distance

With the continuous advancement of RF technology and the concept of the Internet of things getting popular, people proposed new requirements on the automatic IECntification technology, quicker, larger coverage and intellectualized system are needed. UHF RFID technology which has developed rapidly in recent years is to meet these needs. Some products used that technology have been applied to the logistics which has a rapid growth in size and the manufacturing industry with increasingly demanding on automation.They has greatly raised the operational efficiency of these industries.In this paper, a survey about the situation of UHF RFID System research(both domestic and abroad) is conducted. Besides summarize their merits and strengths, some problems like the chaos in communication protocol, short distance for read and write are exposed. On the basis of study of the ISO18000-6 standards, a design of a RF identification reader is made. The operating frequency of the reader is 915MHz, the encoding, decoding, modulation and demodulation operation conformed the ISO18000-6 standards are achieve on the hardware level; according to the requirements of the communications distance a RF power amplifier circuit in the RF transmitter circuit is designed; because the transmitter and receiving circuits share a single antenna and the power in transmitter circuit is much larger than that in receiving circuit, in order to eliminate the interference a circulator is used to isolate the circuits; directional antenna is designed based on rectangular microstrip antenna, during the design process Agilent ADS2009 electromagnetic simulation software is used for simulation and optimization; designed systems software constituted by the hardware connection layer, the communication command layer and protocol layers,the system software achieved the Tag selection, Tag inventory, and Tag access operations conformed the ISO18000-6 standards,and in particular, the system software achieved a anti-collision algorithm based on random time slot mechanism , and in the recognition process,it can transform the parameter about the slot accrding to the number of the tags, with this algorithm ,the interrogator can work well in a multi-tag environment. The RF performance, protocol conformance and remote reading success rate of the prototype system was tested. The result demonstrate that the operating frequency is 916.03MHz, transmit power is 27.5dBm, the tags can be inedtified correctly, the correct recognition rate in ten meters can be above 84% with a microstrip directional antenna. The test proved that the performance of the system meet the expectations in all aspects.