印刷式毫米波寬頻空腔共振天線與陣列之研製

Abstract

本篇論文提出一種設計在毫米波頻段的寬頻空腔共振天線，其使用多層印刷電路板的架構來實現，由一層部分反射面和一層金屬接地面組成，可讓電磁波在共振腔內來回共振以製造高增益之天線特性。本論文首先探討設計部分反射面的反射係數及操作頻率的關係，進而討論將不同的週期性單元結構結合後的部分反射面的寬頻特性，並以傳統均勻部分反射面的空腔共振天線驗證其寬頻的效果。接著對其工作原理進行分析，最後再以一種偶極天線的結構進行實際饋入，完成一個空腔共振天線及天線陣列的設計。本論文所提出的漸變式的空腔共振天線，操作在26.5~29.5GHz的頻率下，其3dB增益頻寬可達11% (傳統均勻空腔共振天線約3%)，天線正向輻射(broadside) 增益可達到15.7dBi，而2x2陣列天線的部分，正向輻射增益可以達到20.6dBi。

This thesis presents a wide-band cavity resonant antenna for the millimeter-wave applications. The antenna employs a multi-layered printed circuit board (PCB) that consists of a partially reflective surface (PRS), a feeding structure, and a ground plane. The confined electromagnetic waves are simultaneously oscillating in the resonant cavity and radiating along the leaking surface for high gain operations. First, we analyzed the relationship between the reflection coefficient of the partially reflective surface and the operating frequency. Second, we discussed the characteristics of the partially reflective surface combined with tapered unit cell of varying periods and validated the broadband effect compared to a conventional uniform cavity resonant antenna. After investigating the working principle, we implemented the realistic structure with a dipole feed and completed the resonant cavity antenna element and array design. The tapered PRS antenna presented in this paper operates in a frequency band of 26.5 to 29.5 GHz. The 3-dB gain bandwidth is about 11%. The broadside gain of the antenna reaches 15.7 dBi for the element design, and 20.6 dBi for the 2x2 array design.