RFID Carrier Phase Accurate Ranging Technology Based On Frequency Hopping

Radio frequency identification technology(RFID)is a technology that uses radio frequency signals to read,write and perceive specific targets.At present,tens of thousands of RFID devices have been successfully deployed in areas such as intelligent transportation and warehouse management.Location-based services(LBS)are one of the important services provided by the Internet of Things,which are all over the industrial and consumer fields.RFID-based indoor ranging technology aims to add location service functions to RFID,combined with hundreds of millions of RFID devices that have been deployed,will be able to play a huge application prospect.Based on this background,on the basis of in-depth research and analysis of the RFID system structure and working principle,this thesis conducts a systematic research on RFID carrier phase precision ranging technology based on frequency hopping.The main research contents are as follows:First of all,for the problem of how to obtain the multi-frequency carrier phase,the signal processing method in the process of multi-frequency carrier phase extraction is studied,mainly including: RFID tag reflection signal detection;tag reflection signal denoising;tag reflection signal deviation correction;channel estimation;decoding,etc.The final experiment shows that the method in this thesis has the characteristics of high detection efficiency,strong anti-noise ability,and accurate carrier phase acquisition.Secondly,for the problem that the carrier phase error causes the ranging error,the relationship between the carrier phase error and the distance estimation error in solving the phase cycle ambiguity.The relationship between the carrier phase error such as Gaussian white noise and the deviation of phase cycle ambiguity solution is clarified.And improved the multi-frequency point carrier phase error suppression algorithm,the experimental results show that the algorithm can effectively improve the ranging accuracy.Finally,using Ettus Research’s software radio platform USRP N210 and Impin J’s commercial reader/writer Impin J R420 to achieve a frequency hopping ranging system demonstration and verification,focusing on the relationship between each link of the system and the carrier phase,the system ranging accuracy and other issues Comprehensive test analysis.Through experiments,the influence of each link of the ranging system on the carrier phase is clarified.Tests show that the average ranging error of the system is close to 2.6cm in a typical indoor environment,achieving high-precision ranging.