Study And Design On Indoor Localization System Based On UHF RFID

With the rapid development of internet of things and the continuous improvementof people’s living standard, the requirement to location based service for people becomeincreasingly strong. The GPS satellite positioning technology has become the maintechnology to achieve location information in people’s living. However, for thecomplicatedly and diversified indoor environment and the badness of received satellitesignal, the GPS localization technology appears powerless. Therefore, there’s lack of akind of effective technology yet to track and positioning persons and things in indoorenvironment that is closely linked to people. Because RFID technology has theadvantage of non-contact, non-line of sight, inexpensive tag and so on, it becomes highprecision and low-cost preferred technology for indoor localization.The thesis firstly introduces the theory, structure, operating frequency and coupledmodes of RFID system. On the basis of related document literature, the thesis thenintroduces the fundamental, characteristic, related example and the achievement ofpositioning parameter, consequently, raises the UHF RFID indoor localization systembased on PDOA ranging as the research contents of the topic. After that, the thesisdeduces the formula of the theory of achieving phase error in PDOA ranging, andproposes IQ demodulation to achieve phase error. For the influence of ranging precisioncaused by selected frequency difference, the thesis proposes the method of dynamicfrequency difference in PDOA ranging. On the basis of the analysis on equivalentcircuit of tag and related document literature, the phase offset caused by the backscatterof tag is corrected to reduce ranging error. Because the actual distance between thereader and tag should be that between the antenna and tag, therefore, the distancebetween the reader and tag was corrected. With that, in the background of3D track andpositioning, the thesis adopts the gradient descent method for still tag’s localization, andthe improved method combining gradient descent and Monte Carlo method for movingtag that may not have enough reader, and meanwhile give out the program flow chart ofthe algorithm. According to the basis demand of indoor localization, the design schemeof whole architecture for indoor positioning system based on CAN bus network ofreader was proposed. Then the thesis respectively designs the hardware structure ofreader and control module, and preliminarily designs its working process.At last, the thesis simulates and analyses the convergence effect of gradient descent algorithm by means of MATLAB, verifies the effectiveness of3D localization of thealgorithm. According to presupposed moving trajectory of tag, the thesis simulates andanalyses the positioning and track effect of traditional and improved Monte Carloalgorithm, verifies the fact that the algorithm also could position and track the tag whenthere isn’t enough reader, and the fact that the track effect of improved algorithm ismuch better than that of the traditional algorithm but has better calculating efficiency.