对同轴电缆布拉格电栅特性的研究

发布时间：2018-04-02 20:19

本文选题：同轴电缆布拉格电栅　切入点：电栅传感　出处：《天津大学》2014年硕士论文

【摘要】：目前,光纤光栅传感器在结构健康监测系统中得到了广泛的应用。但是由于光纤光栅易碎,不能承受大应变力的缺点不能满足大应变力测量的要求。本文采用的同轴电缆布拉格电栅,是依据光子晶体结构方式和光纤布拉格光栅的原理,对同轴电缆进行钻孔形成的栅结构。对同轴电缆进行钻孔破坏了其阻抗连续性,导致在同轴电缆布拉格电栅内传播的电磁波发生发射,其特性和光纤布拉格光栅相似,但是电栅具有更大的尺寸,可以承受更大的张力,可以进行大标距测量的特点,弥补了光纤光栅易碎,可测应变力小,不能进行大标距测量的不足。同轴布拉格电栅具有和光纤光栅相似的传输和反射特性,更具有光纤光栅没有的可承受大应变力的能力,但是国内外鲜有针对同轴布拉格电栅进行的理论分析和仿真。本文首先根据传输线理论和模式耦合理论对同轴布拉格电栅的基本原理进行了阐述,分析了同轴布拉格电栅的电栅效应的机理。然后,对同轴布拉格电栅的结构进行了介绍,并利用传输线原理对同轴布拉格电栅的反射系数进行了推导。接下来采用Ansoft HFSS电磁仿真软件对同轴布拉格电栅进行了建模仿真,Ansoft HFSS是以有限元分析方法作为数值求解电磁场的基础,凭借强大的分析性能、友好简洁的设计界面和后处理器的特点可以对任意形状的三维结构进行电磁场分析。先对均匀的同轴布拉格电栅进行仿真,仿真结果和实验结果进行对比,频率特性基本一致,因此仿真结果可以作为电栅特性研究的依据。最后对相移同轴布拉格电栅进行仿真,可知在相同参数条件下,相移同轴布拉格电栅比均匀同轴布拉格电栅的线宽小,更有利于传感应用。又对相移同轴布拉格电栅不同的钻孔数目、不同的钻空深度,钻孔直径等参数进行仿真,对相移同轴布拉格电栅进行参数优化,进一步减小线宽,提高传感精度。
[Abstract]:At present, fiber Bragg grating sensors have been widely used in structural health monitoring system.However, because fiber Bragg grating is fragile, it can not withstand large strain force and can not meet the requirement of large strain force measurement.The coaxial cable Bragg grating used in this paper is based on the photonic crystal structure and the principle of fiber Bragg grating.Drilling the coaxial cable destroys its impedance continuity, which results in the emission of electromagnetic waves propagating in the Bragg grid of the coaxial cable. The characteristics of the electromagnetic wave are similar to those of the fiber Bragg grating, but the grid has a larger size.It can withstand larger tension and can be used to measure large distance, which makes up for the weakness of fiber Bragg grating (FBG) being fragile, and the measuring strain is small, so it can not be measured at large distance.Coaxial Bragg gratings have similar transmission and reflection characteristics as fiber Bragg gratings, and have the capability of withstanding large strain forces that fiber Bragg gratings do not. However, there are few theoretical analyses and simulations on coaxial Bragg gratings at home and abroad.In this paper, the basic principle of coaxial Bragg gratings is described based on transmission line theory and mode coupling theory, and the mechanism of grid effect of coaxial Bragg gratings is analyzed.Then, the structure of coaxial Bragg grating is introduced, and the reflection coefficient of coaxial Bragg grid is deduced by using the principle of transmission line.Next, Ansoft HFSS electromagnetic simulation software is used to model and simulate the coaxial Bragg gate. Ansoft HFSS is based on finite element analysis method to solve electromagnetic field numerically.The friendly and concise design interface and the characteristics of the post processor can be used to analyze the electromagnetic field of three-dimensional structure with arbitrary shape.First, the uniform coaxial Bragg gate is simulated, and the simulation results are compared with the experimental results. The frequency characteristics are basically the same, so the simulation results can be used as the basis for the study of the grid characteristics.Finally, the phase shift coaxial Bragg gate is simulated. It is shown that the line width of the phase-shifted coaxial Bragg gate is smaller than that of the uniform coaxial Bragg gate under the same parameters, which is more favorable for sensing applications.The parameters of phase shift coaxial Bragg grating such as the number of boreholes the different drilling depth and the diameter of the borehole are simulated. The parameters of the phase-shifting coaxial Bragg grid are optimized to further reduce the line width and improve the sensing accuracy.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TP212;TM248.3

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