基于空间站环境的时间反演电磁通信信道特性及信道估计研究

发布时间：2019-05-22 01:33

【摘要】：时间反演(Time Reversal,TR)技术能够使电磁波在目标点产生空间和时间的同步聚焦,且传播环境中的多径分量越多,信号的聚焦效果越好。空间站环境为典型的复杂多径环境,多径效应所带来的码间干扰严重影响了无线通信的质量与性能。因此,基于时间反演技术构建的新型电磁通信系统非常适合应用于空间站环境。为设计空间站环境中高速、稳定的时间反演电磁通信系统,首先需要研究其信道特性,充分了解时间反演信号的传播规律,为后续的系统设计提供保障,而信道估计也是时间反演电磁系统中的重要部分。因此,本文研究了空间站环境中时间反演电磁通信信道特性和信道估计的相关问题,研究工作主要包括以下三个部分:第一:超宽带(Ultra Wide Band,UWB)时间反演(TR-UWB)电磁系统信道特性及系统鲁棒性的研究。分析了空间站环境中TR-UWB系统的路径峰值功率增益和信道特性参数的变化情况。TR技术能够很好地克服电磁波经过两个太空舱转角处时的大幅信号衰减,同时在空间站各处都能保持比较好的TR信道特性参数。通过分析相关系数和信道特性参数的变化,研究发现接收端在小范围移动时具有较好的鲁棒性。第二:超宽带时间反演多天线超分辨电磁系统信道特性的研究。通过分析亚波长天线阵列信道特性,研究影响时间反演超分辨率聚焦效果的因素,为设计出性能优良的亚波长天线阵列提供帮助,可以提高空间站内通信系统的容量和速率。研究发现时间反演镜天线的数量、间距和刻蚀周期性微结构等对聚焦效果均有所影响,其中亚波长天线阵列的包络相关系数和超分辨率聚焦有着非常紧密的联系,根据天线阵列选择合适的工作频段能够显著的提高超分辨率聚焦效果,也可以用于设计亚波长天线阵列。第三:正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)的时间反演电磁(TR-OFDM)系统中信道估计相关问题的研究。TR技术在OFDM系统中相当于一个滤波器,通过利用TR自适应相位共轭补偿特性来消除多径信道引起的相位旋转,滤波器的参数更新来源于信道估计的结果。研究分析了信道估计在普通多径和复杂多径两种多径环境下对TR-OFDM系统性能的影响,提出了一种基于TR技术的信道估计算法,可以改善下行链路中信道估计的准确性。
[Abstract]:Time inversion (Time Reversal,TR) technique can make electromagnetic wave produce synchronous focusing of space and time at the target point, and the more multi-path components in the propagation environment, the better the focusing effect of the signal. The space station environment is a typical complex multi-path environment, and the inter-symbol interference caused by the multi-path effect seriously affects the quality and performance of wireless communication. Therefore, the new electromagnetic communication system based on time inversion technology is very suitable for space station environment. In order to design a high speed and stable time inversion electromagnetic communication system in space station environment, it is necessary to study its channel characteristics, fully understand the propagation law of time inversion signal, and provide a guarantee for the subsequent system design. Channel estimation is also an important part of time inversion electromagnetic system. Therefore, this paper studies the characteristics of time inversion electromagnetic communication channel and channel estimation in space station environment. The research work mainly includes the following three parts: first: ultra-broadband (Ultra Wide Band, UWB) time inversion (TR-UWB) Channel characteristics and system robustness of electromagnetic systems. The variation of path peak power gain and channel characteristic parameters of TR-UWB system in space station environment is analyzed. Tr technology can overcome the large signal attenuation of electromagnetic wave passing through the corner of two capsule. At the same time, the TR channel characteristic parameters can be maintained all over the space station. By analyzing the variation of correlation coefficient and channel characteristic parameters, it is found that the receiver has good robustness when moving in a small range. Second, the research on channel characteristics of multi-antenna super-resolution electromagnetic system based on ultra-broadband time inversion. By analyzing the channel characteristics of subwavelength antenna array, the factors affecting the super-resolution focusing effect of time inversion are studied, which provides help for the design of subwavelength antenna array with excellent performance and can improve the capacity and rate of communication system in space station. It is found that the number, spacing and etched periodic microstructure of the time inversion mirror antenna have influence on the focusing effect, and the envelope correlation coefficient of the subwavelength antenna array is closely related to the super-resolution focusing. The selection of appropriate working frequency band according to the antenna array can significantly improve the super-resolution focusing effect, and can also be used to design the sub-wavelength antenna array. Third: research on channel estimation in time inversion electromagnetic (TR-OFDM) system of orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing,OFDM). Tr technique is equivalent to a filter in OFDM system. By using the TR adaptive phase conjugation compensation characteristic to eliminate the phase rotation caused by the multi-path channel, the parameter update of the filter comes from the result of channel estimation. The influence of channel estimation on the performance of TR-OFDM system in ordinary and complex multi-path environments is studied and analyzed. A channel estimation algorithm based on TR technology is proposed, which can improve the accuracy of channel estimation in downlink.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN92

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