具交叉極化抑制設計之45度線性極化高增益平面陣列天線

Abstract

本論文中設計一個應用於77 GHz車用前視防撞雷達之45度線性極化高增益天線，操作頻段為76∼77GHz，主要架構由行進波饋入、從饋入線耦合能量給每一個輻射單元串接組合而成。行進波饋入的設計方法可以得到較好的頻寬，以耦合的方式可減少在饋入線上為了匹配或能量分佈所造成的不連續邊所產生損耗及贅餘輻射，且因為利用耦合，可控制每個輻射單元輻射量更小，在設計大陣列天線時能量分布能有更多的選擇。設計45度線型極化最重要考量的因素是需要好的極化性，如此一來偵測物體的時候受到對向車道發射訊號的干擾也相對的小，偵測準確度也會較大，因此也設計了尾端開路殘斷及寄生元件來消除交叉極化。

In this thesis,45-degree linear polarization high-gain planar array antenna applied to 77-GHz vehicle collision warning radar system has been designed, and the operating frequency is 76GHz to 77GHz. The structure uses traveling wave excitation and the energy from the feed line couple to radiation elements. Use traveling wave fed for getting wide impedance bandwidth and use coupling for reducing the discontinuous edge of feed line that would be causing more transmission lose and superfluous radiation when designing energy distribution or matching. The use of coupling can be control the power of radiation of each radiating element smaller, so the energy distribution in the large array antenna would have more choices to design. Beside, the most important consideration for designing the 45 degree linear polarization antenna is having good polarization. The interference of the signal from the car of the opposite lane can be small and the detection accuracy will be better. Therefore, the open stub at the end of the antenna and parasitic elements are designed to suppress cross-polarization.