基于等离子鞘信道测量的寄生调制削弱方法

发布时间：2018-05-31 20:52

本文选题：动态等离子体 + 寄生调制　；参考：《西安电子科技大学》2015年硕士论文

【摘要】：飞行器再入过程中受到空气强大的挤压,与空气发生剧烈的摩擦,从而在其表面形成很强的激波压缩,导致表面的流场内部产生湍流及震荡。覆盖在飞行器表面的等离子鞘套会呈现出复杂的动态特性,导致穿过等离子鞘套的通信信号出现幅度以及相位上的双重调制现象,这种现象称为等离子鞘套的寄生调制效应。寄生调制效应的存在会降低信号传输质量,严重时甚至会致使信息传输中断。削弱由等离子引起的寄生调制效应存在两点困难:一是目前对等离子鞘套动态特性的研究尚不深入,难以准确预测等离子鞘套传输环境;二是寄生调制效应为通信信号引入了一个乘性噪声,不能采用技术成熟的线性滤波方法滤除噪声。针对这两点困难,本文提出两点应对思路:一是研究等离子透射信号与反射信号幅相起伏之间的相关性,通过反射信号对等离子鞘套传输环境进行实时测量;二是通过同态变换方法将频域上相依赖的噪声和信号分离。具体的工作包括:(1)、首先分析了动态等离子寄生调制效应的产生机理和对通信信号造成的影响,并通过实验验证了寄生调制对BPSK、QPSK、FSK以及MFSK四种典型通信信号的影响;(2)、利用基于相关性系数的滑动窗法分析了等离子反射信号与透射信号幅相起伏之间的相关性,为通过反射信号对等离子鞘套传输环境进行实时测量提供理论基础。(3)、论述了反射测量以及同态变换的基本理论,提出了一种动态等离子寄生调制效应的削弱方法,并针对实际应用场景利用Matlab搭建通信系统来验证这种方法的有效性。经过仿真验证表明,本文中提出的动态等离子寄生调制效应削弱方法能有有效减弱寄生调制效应对通信信号的影响。这种方法通过反射信号来推算等离子鞘套信道透射信号的变化,为等离子鞘套下信息可靠传输提供了新的思路。
[Abstract]:In the process of reentry, the aircraft is squeezed by the air, and the friction with the air is intense, which forms a strong shock compression on the surface, resulting in turbulence and oscillation in the surface flow field. The plasma sheath covering the surface of the aircraft presents complex dynamic characteristics, which leads to the amplitude and phase double modulation of the communication signal passing through the plasma sheath, which is called the parasitic modulation effect of the plasma sheath. The existence of parasitic modulation effect will reduce the quality of signal transmission and even lead to the interruption of information transmission. There are two difficulties in weakening the parasitic modulation effect caused by plasma. One is that the research on the dynamic characteristics of plasma sheath is not deep, so it is difficult to accurately predict the transmission environment of plasma sheath; The second is that parasitic modulation introduces a multiplicative noise to the communication signal, so it is not possible to filter the noise by using the mature linear filtering method. In view of these two difficulties, this paper puts forward two countermeasures: first, to study the correlation between the amplitude and phase fluctuation of the plasma transmission signal and the reflected signal, and to measure the transmission environment of the plasma sheath in real time through the reflected signal; Second, the frequency dependent noise and signal are separated by homomorphic transformation. The specific work includes 1: 1. Firstly, the mechanism of dynamic plasma parasitic modulation and its influence on communication signal are analyzed. The effects of parasitic modulation on the four typical communication signals of BPSK, QPSK, FSK and MFSK are verified by experiments. The correlation between the amplitude-phase fluctuations of plasma reflected signals and transmitted signals is analyzed by the sliding window method based on correlation coefficient. In order to provide a theoretical basis for real-time measurement of plasma sheath transmission environment by reflected signal, the basic theory of reflection measurement and homomorphism transformation is discussed, and a method to weaken the dynamic plasma parasitic modulation effect is proposed. Matlab is used to build communication system to verify the effectiveness of this method. The simulation results show that the method proposed in this paper can effectively attenuate the effect of parasitic modulation on the communication signal. This method calculates the change of the transmission signal of the plasma sheath channel by reflecting signal, and provides a new idea for the reliable transmission of the information under the plasma sheath.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：V243.1

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