Research And Implementation Of Passive Wireless Communication System Based On Ambient Backscatter

The ambient backscatter technology is a new type of communication that occurs recently,and the wireless communication between devices is realized through backscatter radio frequency signals as the carrier in the environment.With the rapid development of Internet of Things technology,ultra-large wireless sensor network sensor nodes and micro-embedded devices are getting smaller and smaller,more and more.The problem of powering,routine maintenance,and wireless communication for these large numbers of miniaturized devices is becoming increasingly hard,and traditional battery and AC-powered solutions usually do not work.In this paper,the passive wireless communication system uses the RF signal in the environment as the energy source,and uses the ambient backscatter technology to realize the wireless communication between the passive devices and get rid of the dependence on the battery and the alternating current.The system can make the communication hardware costs and maintenance costs of the micro-embedded devices greatly reduced and can greatly promote the promotion and application of Internet of Things.Therefore,the study of passive wireless communication system is of great significance.In this paper,we focus on how to improve the energy collection efficiency,communication rate and communication distance of passive wireless communication system.The main contents and work include:(1)The basic principle of environmental electromagnetic energy collection is carefully studied,and the impedance matching circuit between antenna and load is designed according to impedance matching principle and Smith circular graph.A theoretical model of N-class RF-DC charge pump booster rectifier circuit is analyzed and established.The relationship between the output voltage,the conversion efficiency and the charge pump series is analyzed according to the equivalent model of the diode,and the simulation is carried out by MATLAB.Finally,a 5-stage RF-DC charge pump booster rectifier circuit was designed and tested with an energy recovery efficiency of up to 51%.(2)This paper studies the principle of data transmission and modulation of ambient backscatter technology and its energy transfer process,completes the RF switch test and selection,designs TI's MSP430G2553 as the control chip and designs the passive transmitter.The intensity of the backscatter signal is tested and the signal strength is about0.7 dBm.(3)An ultra low power multi-antenna decoding algorithm is proposed.Thetheoretical model of the algorithm is analyzed in detail,and the hardware implementation of the algorithm is completed in the simulation domain without using high-power devices.The passive receiver is designed with the algorithm as the core,the hardware circuit design is completed,and the hardware circuit of the passive receiver is simulated and tested.Finally,the test platform of passive wireless communication system is set up.The communication rate and communication distance are tested.The results show that the proposed algorithm can improve the communication speed from 1kbps to 50 kbps and increase the communication distance from 2.5ft to 6 feet.