無線寬頻存取天線及導波管轉換之設計

Abstract

本論文探討無線寬頻存取天線以及導波管在Ka頻段轉換。無線寬頻存取主要是操作在頻率為28GHz的系統。而這個系統所需要的是一個需要高增益，輻射場形主波束很窄的天線。而利用導波管饋入的微帶貼片陣列天線以及雙反射型天線，我們可以得到高增益，窄主波束的特性。本論文中微帶貼片陣列天線的設計方法為先設計一個導波管饋入的子陣列，再在導波管做能量分佈，而完成整個陣列。而雙反射型天線為使用科西格蘭亦即雙曲面的子反射板加上拋物面的主反射板製作而成的天線。而這兩個天線的共同特點為饋入時都需使用導波管，於是我們後來又做了一個導波管到微帶線的轉換，以配合前級電路，而在導波管對微帶線的設計上，我們設計了一組可調式的backshort結構以利於在不同材質，及製作上頻率誤差所需的手動式調節，最後綜合以上的設計，去完成無線寬頻存取的天線以及連接前端電路的轉換，並實際量測，以驗證所設計的天線及導波管轉換的可行性。

In this thesis, we will discuss local multipoint distribution service (LMDS) antennas and waveguide transitions in Ka-band. First, the antenna applied in the system is high gain, and narrow beamwidth. Reflector antennas and microstrip patch antennas can achieve the goal. In this thesis, we will focus on microstrip patch antennas. A m ajor restriction of high gain microstrip antenna arrays is their high loss, mainly due to the feeding network. Waveguide feeding network is low-loss applied in the microstrip antenna arrays. Interconnections between the planar structures and waveguide feeding network are done via slot coupling. The waveguide feeding network for this antenna is machined from aluminum manufacture, and electroplated to realize low-loss, low-cost planar antennas. Second, we will design waveguide-to-microstrip transitions, including the fixed and tuned backshort. The tuned backshort in the transition is convenient for us to apply in different band and to use other substrates. From these two designs, we can get a small-size, low-profile, convenient component in LMDS systems.