具高隔離度特性的24-GHz高指向性共振腔雙天線設計

Abstract

本論文中將提出一個應用於汽車防撞雷達前視系統的高指向性共振腔天線，操作頻段為24.025GHz~24.225GHz，主要架構由微帶型天線、部分反射平面(Partially Reflecting Surface-PRS) 以及金屬邊牆所組合而成，利用天線輻射在共振腔內進行多重反射最終達到穩定模態進而產生高增益的輻射場，在整體高度上相對於一般常用的透鏡天線(Lens Antenna)可以有大幅度的縮減。 為了彌補共振腔天線大面積的缺點，我們將會討論饋入位置偏移中心對電場分佈的影響，進而將雷達的收發雙天線置放於相同的共振腔以達到面積縮減的目的，最終比較各種去耦合電路的特性，將天線結合全波長共振器來產生抵消路徑，達到二埠之間寬頻的高隔離度特性。

In this thesis, we introduce a design of high directivity cavity antenna applied to 24GHz forward-looking collision avoidance radar system, 24.025GHz to 24.225GHz is the operating frequency. The major model is structured by patch antennas, the partially reflecting surface (PRS) and metal sidewalls. The multi-reflection of antenna radiation in the cavity is applied to reach higher gain and narrow beam, and miniaturize total height compared with the height of Lens Antennas. Making up for the huge area of cavity antennas, we will analyze the electric field distribution affected by shifting the feeding position and then install the Rx and Tx antennas in the same cavity to reach the area miniaturization. Lastly we compare the characteristics of some different decoupling circuits. By combining the antenna and the one wave length resonator to generate another path, which cancels the antenna coupling, finally we can achieve a high isolation antenna for wide-band.