與介質透鏡共同設計之折疊式反射陣列天線應用於77GHz雙模態前視車用防撞警示雷達系統

Abstract

本論文將提出一應用於雙模態前視汽車防撞雷達系統的天線設計，利用反射陣列天線以及透鏡天線的共同設計，當此系統操作在遠距離模態時(操作頻率76GHz-77GHz) ，此天線具有高指向性的特性，且主波束偏向需求的角度，配合演算法作遠距離車體的偵測；操作在近距離模態時(操作頻率77GHz-81GHz)，具有較寬的3dB波束寬，並利用開關切換左方及右方天線，可涵蓋較廣角度範圍，對近距離車體有較廣範圍的偵測。而本論文提出的架構可將遠距離模態以及近距離模態的天線整合至一體，縮小面積，甚至可將後端積體電路置於此面積下。 此天線由饋入天線、主要反射基板、子反射基板、半圓柱形透鏡組合而成。在此架構下，可利用饋入天線不同的輻射電場極化方向而分別達成遠距離模態及近距離模態的操作，此二模態最後都經由半圓柱型透鏡集中垂直地面方向的輻射能量，完成整個設計。 利用此概念可將操作於不同模態的發射、接收天線共九組整合至同一架構中，共用面積，共用透鏡，進而縮小整體所需的面積及成本。

In this thesis, we proposed a novel antenna structure for the application of the dual-mode forward-looking collision warning radar system. By the co-design of the folded-reflectarray antenna and the dielectric lens, a dual mode operation can be realized. When the radar system is operated in the long range mode (76GHz-77GHz), the antenna had high-directivity characteristic. To cooperate with the algorithm used in the long-range mode, the main-beam should point to the angle we desired. Otherwise, the antenna operated in the short-range mode (77GHz-81GHz) has wide 3dB-beamwidth. By switching the antennas focused on the left-hand side and the right-hand side, the angular range covered would be wider. The antenna we introduce in this thesis has the advantages to integrate the two different modes in one structure, miniaturize the total size and further comprise the IC in the same structure. The antenna composes of feed antennas, main-reflector, sub-reflector and cylindrical lens. In this structure, the antennas used in the two different modes (long-range mode and the short-range mode) can be separated by the different polarizing directions of the feed antennas. It is noticed that all the antennas in the structure would focus the radiated power in the vertical by the cylindrical lens. Totally nine antennas used for different functions (transmit or receive ) and modes(long-range mode and the short-range mode) would be integrated in the structure. By sharing the area and the lens, the size and cost can be reduced.