Comprehensive Channel Characteristics And Measurement Methods For Hypersonic Vehicle

When hypersonic vehicle is flying in the near space,the bad communication environments such as large Doppler and dynamic plasma sheath,make it difficult to use effective communication methods to realize the communication and control of the vehicle,which seriously restricts the reliable information transmission of the hypersonic vehicle.In order to study the new communication methods in the plasma sheath environment,we must first recognize the channel characteristics of the hypersonic vehicle comprehensive channel,and the most intuitive way to recognize the channel characteristics is to detect the channel.However,the poor communication environment makes the traditional channel detection technology unable to apply to channel detection under hypersonic condition directly.Therefore,it is of great significance to study the new technology of comprehensive channel detection for hypersonic vehicle,and provide data support for the research of new communication methods under plasma sheath environment.The contents and main work of this paper are as follows:1.The comprehensive channel characteristics of hypersonic vehicle are analyzed.Firstly,the power loss characteristics,the Doppler effect and the corresponding parameter extraction methods of the high-speed mobile fading channel are analyzed.Secondly,the dynamic characteristics of the dynamic plasma sheath,the characteristic of the signal propagation and the channel characteristics of the plasma sheath are analyzed.Finally,on the basis of the channel characteristics of the above two channels,the comprehensive channel characteristics of hypersonic vehicle are summarized,so that the theoretical performance analysis of the detection methods can be performed.2.For the comprehensive channel characteristics of hypersonic vehicle,two kinds of channel detection methods are improved,and the theoretical performance simulation of the detection method under hypersonic condition is performed.According to the comprehensive channel characteristics of low signal to noise ratio,fast time-varying and large attenuation of the hypersonic vehicle,the requirements of the channel detection scheme are analyzed.According to the analysis of the detection signal to meet the characteristics of the constant envelope,the chirp spread spectrum signal and CAZAC(constant envelope and zero autocorrelation)sequence are selected as the detection signals of the hypersonic vehicle comprehensive channel and the scheme of pulse compression and cyclic sliding correlation is selected as the main channel detection system.Considering the selection of detection signal and detection system,the existing pulse compression detection scheme based on chirp spread spectrum signal and the sliding correlation detection scheme based on CAZAC sequence is improved respectively,and two schemes that can be applied to the integrated channel detection of hypersonic vehicles are obtained: Pulse Compression detection scheme based on CAZAC sequence and cycle slip correlation detection scheme based on CAZAC sequence.In view of the characteristics of hypersonic vehicle comprehensive channel,the theoretical performance simulation of the several detection schemes is performed.The simulation results show that the detection performance of cyclic sliding correlation detection scheme based on CAZAC sequence is obviously better than other detection schemes,which can detect the fast time-varying fading channel with a signal to noise ratio of-20 d B and a time-varying rate of 200 k Hz accurately and meet the detection requirements of the hypersonic vehicle comprehensive channel.3.The ground simulation experiment is carried out to verify the detection method.Dynamic plasma sheath channel environment is simulated by the DPSE02(second generation dynamic plasma science experimental device),the high-speed mobile fading channel is modeled by EB F8 channel simulator,and the two channel environments are cascaded to form the comprehensive channel environment of hypersonic vehicle.Based on the established channel environment,the cyclic sliding correlation detection scheme based on CAZAC sequence is verified under different experimental conditions.The experimental results show that when the plasma change frequency is 200 k Hz,the detection error of the proposed scheme is 0.1k Hz,which can be ignored.The maximum Doppler frequency offset,the spectrum expansion and the probability density distribution of the amplitude and phase for high-speed mobile fading channels with different flight speeds and angles of flight can be accurately extracted.And the plasma change frequency and the Doppler power spectrum of the hypersonic vehicle comprehensive channel in different frequency bands can be accurately estimated.Therefore,the cyclic slip correlation detection scheme based on CAZAC sequence can meet the requirement of channel detection in hypersonic vehicle environment.