具波束掃瞄能力之新型毫米波折疊式微帶反射陣列天線

Abstract

本論文提出一個具波束掃瞄能力之新型毫米波折疊式微帶反射陣列天線，文中包括了設計，模擬以及量測的結果，另外也提出一個適用於此天線的機械式波束掃瞄方式。新型毫米波折疊式微帶反射陣列天線包含三部分：主反射板，次反射板以及饋入天線。主反射板是一個圓形平面，包含數百個微帶天線，主要用來轉換電磁場的極化方向以及補償電磁波的相位差，以達到聚焦的效果。次反射板是一個由上含高密度平行印刷金屬線之毫米波基板，主用於電磁場的極化方向選擇，它可以反射某一極化方向的電磁場，讓另一極化方向電磁場通過。饋入天線是矩型的微帶天線，是負責折疊式微帶反射陣列天線的能量饋入與接收，而它可以在主反射板上移動，不同的饋入天線的位置將會造成不同的主波束角度，以達到主波束的掃瞄。我們介紹的新型毫米波折疊式微帶反射陣列天線有容易製作，低成本，以及縮小體積等等的優點。在應用方面，這一型的天線可以應用於點對點的無線通訊迴路，以及汽車雷達等等。此天線有25dB左右的增益，旁波瓣比是-15dB，半功率頻寬有5.5％，4.6度的半功率波束寬，論文中也實現了7.2度的掃瞄角度。

Thesis proposes a new beam-steering millimeter-wave folded reflectarray antenna using printed-circuit planar reflectors. The folded reflectarray antenna contains three parts: a main reflector, a sub-reflector, and a feed antenna. The main reflector includes hundreds of microstrip antennas used to produce twisted re-radiated fields and provide phase compensation for focusing. The sub-reflector parallel with the main-reflector is made of a substrate printed with high-density metal grid, which is transparent to one polarization but would reflect the other polarization. The feed antenna is a microstrip patch antenna located on the main reflector. The position of this feed antenna is movable so as steering the radiation beam of the antenna. Measured results showed good agreement with the calculated ones. The finished antenna has a gain of 25dBi gain, side-lobe lower than -15dB, and 3-dB beamwidth of 4.6 degrees. A beam scanning range of 7.2 degrees is achieved when the position of the feed antenna is varied by 8mm. This antenna has low profile configuration and suitable for mechanical beam scanning or electronic beam switching.