Research On Channel Distortion Cancellation Method Of High-speed Aircraft In Complex Electromagnetic Environment

In recent years,hypersonic vehicles have become the research hotspot of the world’s space powers,and reliable measurement and control technology as "ears and eyes" has also become one of the key technologies.The traditional unified carrier measurement and control communication system based on S-band is limited by the characteristics of low operating frequency and narrow frequency band,which cannot meet the future hypersonic aircraft’s requirements for high-speed data transmission,large bandwidth,installation space,overcoming "black barrier" and anti-interference Demand,Ka-band measurement and control technology has become a new trend in the development of international aerospace technology.However,when the high-speed aircraft is flying at high speed in the Ka communication frequency band,the non-linear characteristics of its internal high-power amplifier will introduce inter-symbol interference,causing nonlinear distortion of the channel.In addition,the hypersonic vehicle will be affected by large dynamic Doppler frequency shift,plasma sheath deep fading and multipath effects during flight,and the channel exhibits deep fading and fast time-varying characteristics.The complicated electromagnetic environment makes the existing communication system unable to adapt,and it is difficult to achieve reliable measurement and control communication.In response to this problem,this paper aims to eliminate the channel distortion caused by the complex electromagnetic environment of high-speed aircraft,and carries out two aspects of work: high-speed aircraft nonlinear channel distortion cancellation and high-speed mobile mobile channel distortion cancel ation.1.Based on the polynomial model,the nonlinear distortion simulation of the Ka-band RF power amplifier is realized,and the nonlinear distortion cancellation of the Ka-band RF power amplifier is completed by using the LMS algorithm.The nonlinear characteristics and behavior models of the power amplifier are analyzed in detail.O n this basis,the power amplifier distortion model of the Ka band of the high-speed aircraft is fitted;the nonlinear predistortion learning structure of the power amplifier and the adaptive cancellation algorithm are studied,and the Ka Simulation study on nonlinear channel distortion cancellation of frequency band power amplifier.The simulation results show that the nonlinear characteristics of the power amplifier will seriously interfere with the transmission signal.In the absence of pre-distortion correction,the bit error rate of the system can be achieved after pre-distortion,and the error performance has been improved by 3-4 orders of magnitude.The effectiveness of the proposed predistortion scheme.2.An iterative feedback channel equalization algorithm for Doppler information-assisted channel estimation is proposed to complete the integrated wireless channel distortion cancellation for high-speed aircraft.Aiming at the characteristics of high-speed mobility of the channel under high-speed aircraft,the ability of the traditional channel estimation equalization algorithm to deal with normalized Doppler frequency shift greater than 0.1 is analyzed.Based on the traditional algorithm,an iterative feedback channel equalization algorithm of Doppler information-assisted channel estimation is proposed.By using Doppler information,the fast time-varying channel with a normalized Doppler frequency shift greater than 0.1 is effectively estimated.Iteratively eliminate the fast time-varying interference items,and finally add spread spectrum communica tion to further improve the system’s anti-black-blocking interference performance.The simulation results show that the proposed algorithm can meet the communication requirements through three to four iterations of bit error rate performance.The performance of the algorithm after the auxiliary channel estimation of the Lele information estimation is improved by 3-5d B compared with the algorithm without Doppler correction.3.The simulation of the integrated channel environment is realized,and the experimental verification of the proposed channel cancellation method is completed on this basis.Considering Ka-band nonlinear channel,high-speed mobile channel and plasma sheath channel comprehensively,the integrated channel environment with nonlinear and fast time-varying characteristics is simulated.The effectiveness of the two distortion cancellation methods proposed is comprehensively evaluated.The simulation results show that the distortion cancellation method proposed in this paper can effectively reduce the communication interference caused by complex channel environment.The normalized Doppler frequency shift is 0.1,when the frequency of the plasma sheath channel changes to 100 k Hz,the simulation results show that the proposed method can reduce the bit error rate to below 10-3,compared with the traditional algorithm system performance has been significantly improved,can effectively improve the communication quality.In summary,this paper studies the fire protection method by channel distortion in the complex electromagnetic environment of high-speed aircraft,which can largely eliminate the impact of the complex electromagnetic environment,significantly improve the reliability of communication,and alleviate the "black barrier" problem.It is very important.