使用FR4基板之2.5GHz及24GHz微帶天線陣列研製

Abstract

本論文主要目的為研製24GHz天線陣列於FR4基板，擬應用於車用防撞雷達，用以減少量產成本。論文有關2.5GHz天線陣列研製，係做為循序旋轉及相位饋入陣列架構驗證，根據調頻連續波(FMCW)雷達原理，增加操作頻寬可提高雷達距離及速度解析度，天線元素使用截角微帶天線，並配合循序旋轉及相位饋入設計天線陣列，提高軸比頻寬及阻抗匹配頻寬，並採用圓形極化天線，以減少目標物二次反射干擾。循序相位饋入架構使用λ/4及3λ/4長度之微帶線，再經由適當排列方式縮小2×2陣列元素間距及降低旁波瓣，並採用兩次循序旋轉饋入架構設計4×4天線陣列，以提升天線增益，減少波束寬度。24GHz天線陣列增益量測使用電波組遠場天線量測設備，4×4天線陣列量測增益約為7.6 dB，3dB波束寬為22度，顯示FR4基板可應用於低成本24GHz車用防撞雷達設計。

The purpose of this thesis is to develop a 24 GHz antenna array using FR4 substrate in order to minimize the production cost. The 24 GHz antenna array will be applied in the automotive collision avoidance radar. The use of 2.5GHz antenna array is to verify the sequentially rotating array architecture. According to the frequency modulated continuous wave radar, increasing the operating bandwidth can improve the radar range resolution and speed resolution. The array element is a truncated microstrip antenna. The sequential rotation and phase feed antenna array is then applied to improve the axial ratio bandwidth and broadband impedance matching. The antenna array uses circular polarization in order to reduce the secondary reflection interference. λ/4 and 3λ/4 microstrip lines are used with proper feed lines to give a compact 2×2 sequential phase feed structure and reduce the side lobes. Two sequentially phase feeds are utilized to design a 4×4 24 GHz antenna array to increase the gain and reduce the 3dB beam width. Antenna arrays are measured using the far-field antenna measurement facility in EM group. The 4×4 antenna array gain is about 7.6 dB with 22° for 3dB beam width to indicate FR4 substrate can be applied in a low cost 24GHz car collision avoidance radar.