Research On Baseband Self-interference Signal Cancellation Technology For UHF RFID Reader

In recent years,the importance of Internet of Things technology has been noticed by governments,enterprises and academia around the world.Radio Frequency Identification(RFID)technology,one of the key technologies of the Internet of Things,has also become a research hotspot.Due to far recognition distance,fast recognition speed and large information capacity,UHF RFID technology is widely used in production,logistics,anticounterfeiting,asset management,etc.According to the backscattering communication principle of the system,the UHF RFID reader transmits a continuous carrier signal when reader receives the signal that the tag returns carrying the tag information.In this process,the continuous carrier signal transmitted by the reader will enter the reader receiving channel due to insufficient isolation of the circulator or directional coupler,and thus become a self-interference signal that affects the reception and recognition of the useful signal.The existence of self-interference signals affects the reader's receiving performance seriously.Therefore,how to suppress self-interference signals has become the focus of research on the reader's receiving sensitivity improvement.The main research contents of this thesis are as follows:1.From the perspective of the backscatter communication principle of UHF RFID system,the source and generation principle of self-interference signal are analyzed.The mathematical model of the backscattering communication channel of the UHF RFID system is established.The characteristics of the self-interference signal are deduced,and the influence of the self-interference signal on the receiving performance of the reader is analyzed.2.In order to suppress the self-interference signal and improve the receiving performance,the baseband self-interference combined cancellation solution is designed.The working process is divided into two steps: self-interference channel estimation and baseband self-interference cancellation.Self-interference channel estimation is divided into two steps: rough estimation and accurate estimation.The principle of adaptive filtering is studied.By analyzing the performance of different adaptive algorithms,the optimization algorithm is applied to the reconstruction of baseband self-interference signals.3.Verify the baseband self-interference signal cancellation effect.Firstly,thetheoretical effect of the adaptive digital self-interference cancellation system is derived by formula.The simulation model of self-interference combined cancellation system is built,and the simulation effect of adaptive digital self-interference cancellation is analyzed.The influence of the phase difference between the self-interference signal and the local oscillator of the downconverter on strength of the baseband self-interference signal and the self-interference cancellation effect is analyzed.Finally,the receiving sensitivity test platform is built,and the actual effect of the baseband self-interference signal combined cancellation solution on the reader's receiving performance improvement is verified.It is verified that the baseband self-interference cancellation system can improve the reader's receiving performance.