Key Technologies And Verification Of Active Electromagnetic Interference Cancellation In Vehicle Loads System

With the development of wireless communication technology,information-based warfare has become a trend,and communication equipment with various functions are intensively deployed in the vehicle loads system.Communication devices transmit and receive data in adjacent or the same frequency band at the same time,resulting in serious electromagnetic interferences among the frequency-using devices of the vehicle platform,reducing the transmission quality and even causing interruptions of communication.In order to ensure the in-vehicle communication equipment to work properly,the thesis uses active electromagnetic interference cancellation technology to solve the mutual interference between communication equipment.The thesis is mainly as follows:Firstly,the application scenario of active electromagnetic interference cancellation technology is systematically analyzed,and a polynomial model of the interference signal received in the digital domain is established.To improve the effect of interference cancellation,combined with the application scenario,an active interference canceling system structure based on the feedback from the RF front-end of the interfering device is adopted,which can effectively suppress the nonlinear components of the transmitting interference signal and thermal noise.Based on the above structure,a received signal model containing multipath effect,fractional time delay and receive channel nonlinearity is derived.Secondly,a digital interference cancellation algorithm with time-delay robustness is designed,and the impact of engineering non-ideal factors on the interference cancellation performance is simulated and analyzed.To reduce the impact of the uncertain propagation delay of the interference signal on the cancellation performance,an interference cancellation algorithm with time-delay robustness is designed by considering the uncertain propagation delay of the interference signal,the nonlinear effect of the RF device,and the hardware implementation complexity constraint.The effectiveness of the algorithm is verified by establishing simulation models and testing the influencing factors such as fractional-order propagation delay,multipath effect,forgetting factor and desired signal power.The simulation results show that when there is a maximum error of 50% symbol offset,the bandwidth of the interfering signal is2 MHz,and the signal-to-noise ratios of the received interfering signal and the desired signal are both 40 d B,an interference cancellation ratio of about 38 d B can be achieved,and the signal-to-noise ratio of the desired signal is degraded by no more than 3d B.Thirdly,the hardware implementation and experimental verification of the interference cancellation algorithm with time-delay robustness are completed.The overall implementation architecture of the universal software radio peripheral is given.The interfaces,structures and functions of each interference canceling core module are designed in detail,and the hardware resource consumption after layout is analyzed.A verification platform is built in a laboratory environment to test the performance of the interference canceling algorithm designed in this thesis.The results show that the actual interference cancellation capability is reduced by about 3d B compared with the computer simulation results due to the influence of data fixing accuracy and the RF non-ideal factors of the test equipment.The research results of the thesis can be applied to the scenarios of dense deployment of frequency-using equipment such as vehicle,shipboard and airborne,to solve the mutual interference problem among multiple frequency-using equipment,and to provide theoretical and methodological support for the co-location interference suppression of integrated platforms.