Research On Indoor Passive RFID Positioning Technology Based On Multi-Frequency Phase Difference Ranging

In recent years,with the breakthrough of intelligent technology,the service model based on location information has become a hot spot in all walks of life.Because indoor is the main activity place of modern people,it is of great significance to obtain indoor location information quickly and accurately for realizing the interconnection of everything.Although satellite positioning technology has basically matured in the outdoor environment,the satellite signal will be shielded in the indoor environment,so the positioning effect is not good.Positioning technology based on radio frequency identification(RFID)has become a key technology for domestic and foreign scholars to study indoor positioning due to its advantages of easy deployment,non-contact and low cost.At present,the mainstream method of RF positioning is mainly based on the received signal strength indicator(RSSI)for positioning,but RSSI is greatly affected by environmental interference resulting in poor positioning accuracy,so this thesis uses the multi-frequency characteristics of RF phase to propose an indoor passive RFID positioning method based on multi-frequency phase difference ranging.The error sources of phase measurement are analyzed and corresponding error suppression methods are proposed.On the basis of studying the phase acquisition and error models,the influencing factors of phase measurement are analyzed,and the coupling effect experiments of tags are carried out to analyze the interference of adjacent labels,and the systematic factors and noise factors of phase error are suppressed by reference tag calibration method and Gauss-Kalman filtering method,respectively,to reduce the volatility of phase data.To solve the problem of period ambiguity of phase,the Chinese residual theorem based on closed solution is studied.A multi-frequency carrier phase difference-distance model is proposed.Different phase difference information is obtained by transmitting carrier signals of different frequencies,and the distance is solved by using the Chinese residual theorem.The simulation results show that the positioning accuracy is improved compared with the traditional Chinese residual theorem.An improved indoor positioning method based on weighted Levenberg-Marquardt(LM)is proposed to optimize the position coordinates of the solution target and ensure the convergence of the ranging equation system solution positioning.Experiments are carried out in the actual indoor scene,and the experimental results show that the average error of the positioning algorithm in this thesis is 0.38 m,and the maximum error is0.5m,which can meet the needs of indoor positioning.This thesis has a total of 39 pictures,3 tables,and 80 references.