Research And Design On Radio Frequency Front End Circuit Of UHF RFID Reader

RFID is a new technology of non-contact automatic identification which booms up in recent several years.Presently,both in theory and practice application aspects,it comes to the front more and more,which of UHF RFID technology is the most advanced in the world.RFID technology in UHF band has advantages of long identification distance,speedy identification,relatively long life and so on which is applied to these domain electric street nameplate,freeway charge,Logistics Management and Strategy and tracking of products.In the nearly future,the development of UHF RFID reader if perfect foreground,for the technology of RFID will be instead of bar code step by step and dominate in EPC.At present,the domestic researching based on UHF reader is still in its primary stage.Aiming at the weakness of RF analogy front end circuit in UHF RFID reader, such as too many components,high cost,high power consumption,and so on, topology,parameter selection and circuit design are analyzed and studied in detail in this paper.The main contents are as follows:Firstly,the development,system structure of RFID and the working principles of UHF RFID system were introduced,the ISO/IEC 18000-6 type B standard was analyzed,and the theory of RF communication system was researched.On the basis of these discussion,the paper proposed the overall design diagram of the reader.Secondly,this paper designs the PLL circuit based on digital frequency synthesizer PLL400-915.Design uses a pseudo-random frequency hopping control,to avoid electromagnetic interference with the environment,as well as the weak of RF signal caused by multi-path effects of the environment,and the success rate of reading and writing were improved.By choosing appropriate RF IC,this paper designs the RF modulation circuit,RF power amplification circuit and power management circuit which are compatible with the ISO/IEC 18000-6 type B standard.The reader power consumption is reduced effectively,for the reader output power is adjustable and the RF amplifier supply is managed.Thirdly,to the receiving circuit,the right IC was chose according to the features of the UHF RFID reader.And a dual-channel zero-IF receiver detection circuit was designed to reduce the reader cost and power consumption further.At the same time, a voltage doubler detector was adopted to get higher output voltage.The receiver sensitivity was improved also.Finally,according to the system design requirements,a UHF RFID reader prototype was developed.Its hardware was experimented and debugged,the experimental results were present,and the related issues in the debugging process were discussed.The test results show that the prototype's output power,read distance and power consumotio are attained the design standards required.The prototype can work stably and achieve the expeted goals.