基于微波色散器件的成像系统设计

色散一词常用于光学，是指材料的折射率随入射光频率的改变而改变的性质。 微波频率下，色散是指电磁器件的波矢 k 具有的随频率变化的特性。微波色散器 件可分为导波传输线和辐射天线两类，导波结构建立了电磁波沿传输线方向的相 位信息与频率的对应关系，而色散辐射天线可以建立天线波束角度与频率的对应 关系。漏波天线就是一种常见的色散性天线，具有波束扫描角度随频率变化的特 性，可从频率维度对空间信息进行高速感知和成像，在微波成像中具有重要的应 用。另一方面，在搭建成像系统时，系统带宽越宽，往往能够获取到更多的信息， 但现有的无线通信系统在进行高带宽信号收发时，可能会受到接收端采样率的限 制而无法收到完整的信号，具有特殊相位色散特性的导波传输线——相位器 （Phaser）便可以解决这一问题。利用相位器对接收信号做时间拉伸（Time Stretch）， 能够在采样率不足的情况下仍能采得完整信号。基于上述两点，本文的主要研究 工作如下： 基于相位器的微波时间拉伸系统设计。本文基于光子时间拉伸的原理，提出了 一种微波频率下的时间拉伸系统。利用 C-Section 结构在高工作带宽下设计了具有 较高线性群时延响应的相位器。利用设计的相位器搭建了一至多路微波时间拉伸 系统，在采样率不变的条件下将接收端得到的采样点数提高 2—4 倍。 基于微波时间拉伸的一维成像系统设计。本文将时间拉伸原理应用于一维成像 系统的搭建中，该系统基于一种频率分集的近场成像算法来对被测物体进行探测。 利用相位器的时间拉伸功能对成像系统进行了改良，使其能够在采样率只有 1GS/s 的情况下仍能保持所需的 1GHz 成像带宽，从而较好地实现了对散射体在一维方向 上位置信息的重构。 基于高扫描率漏波天线阵列的三维成像系统设计。本文设计了一个基于开缝 SIW 结构的高扫描率漏波天线，天线实现了 6.26°每相对带宽的高扫描率。随后在 所提出的漏波天线结构的基础上，设计了 MIMO 漏波天线阵列并将其用于搭建一 个三维成像系统。该成像系统能够在 10mm×10mm 的像素精度下准确定位散射体 的位置，并能精确重构出物体的三维形状。

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