Design And Implementation Of Noncoherent Receiver Algorithm For Ambient Backscatter Communication System

Ambient backscattering is a low-power communication technology.The backscattering device switches the impedance matching state through a switch,thereby loading its own information on the ambient signal,saving spectrum resources.At the same time,the backscattering equipment has low cost and low power consumption,and is suitable for application in the Internet of Things.The signal received by the receiver includes a direct link signal and a reflected link signal.Generally,the power of the direct link signal is several orders of magnitude higher than that of the reflected link signal,and it is difficult for the receiver to recover the backscattered signal.The design of the receiver is a key issue in the Ambient Backscatter Communication System(ABCS).The signal detection of the receiver can be divided into coherent detection and non-coherent detection.Coherent detection requires carrier phase information,and the computational complexity brought by channel estimation greatly reduces the communication performance of low-power ABCS,which is difficult to meet the communication requirements of the Io T.This thesis studies the ABCS incoherent receiver algorithm,avoiding the increased computational complexity of channel estimation,and studying the communication performance of ABCS such as communication distance,bit error rate and data throughput.The FSK and ASK modulated information are carried on the frequency and amplitude respectively.Communication systems based on FSK and ASK modulation generally use non-coherent receivers.Due to the strong interference of ABCS,the traditional ABCS adopts single-sideband FSK modulation.This modulation method that ignores the negative half-axis sub-carrier causes 3d B of information loss and reduces the performance of the receiver.In this thesis,a quadrature correlator incoherent receiver algorithm is proposed to demodulate weak environmental backscatter signals based on double-sideband FSK modulation.The simulation results show that ABCS with double-sideband FSK modulation is very suitable for short packet communication when the energy budget is limited and the channel is Rayleigh,Rice,or no fading.ABCS has the characteristics of low power consumption,and the OOK modulation method is often used on the tag side,but compared with other modulation methods,the OOK modulation method is more susceptible to interference from strong direct link signals.Based on the pattern decoding that eliminates the inherent fluctuation of the signal,this thesis proposes the frequency shifting(FS)ABCS non-coherent receiver algorithm,which reduces the carrier self-interference by transferring the received signal to the adjacent channel.Experimental research shows that,compared with the traditional incoherent receiver algorithm,the algorithm proposed in this thesis is more robust to the fluctuation of the carrier signal and expands the communication range of the system.Although the frequency-shifted ABCS receiver algorithm weakens the carrier interference to a certain extent,it is still difficult to extract data from the frequency-shifted original signal due to the low signal-to-noise ratio of the frequency-shifted backscatter.In order to further improve the communication performance of ABCS,this thesis separates the received signal through multi-stage filtering,and then inputs it to the decoding algorithm.The experimental results show that compared with the traditional method,the multi-filter design applied in this thesis significantly improves the throughput performance of ABCS.At the same time,the bit error rate performance has also achieved good results in various communication environments.The thesis has 54 pictures,4 tables,and 92 references.