77GHz車用雷達串聯微帶天線之設計

A Series-Fed Microstrip Antenna for 77GHz Automotive Radar

本論文使用液晶聚合物（Liquid Crystal Polymer）薄膜，設計應用於77 GHz汽車雷達的串聯微帶天線。所提出的天線是基於傳輸線模型分析方法所設計。操作頻帶在75.42～81GHz，結合串聯和並聯兩種饋入的方式設計，使其整合天線的增益和頻帶符合需求。為提高雷達探測目標辨識的能力，主波束與旁波束比值需大於10 dB，論文中，串聯天線與並聯饋送網路架構可以依據操作頻率初步決定天線及饋送網路之尺寸，但主波束和第二旁波束相差8.9db，主波束和第二旁波束的比值可以藉由嵌入式饋入架構來改善，提高約0.44 dB，最後再調整天線貼片的寬度來降低其旁波束增益，主波束和第二旁波束相差可大幅提高到11.6dbi。模擬結果顯示所設計的陣列天線，其頻率操作範圍可由75.42GHz到81GHz，最大增益值可達17.25dBi，具有高增益和寬帶寬的特性，可以應用於車用雷達。

In this paper, a 77GHz series-type microstrip antenna array for automotive radar applications is designed and simulated. The liquid crystal polymer film with stable dielectric constant and low loss tangent at the mm-wave range is used for this purpose. Based on the transmission line model, the parameters related the designed antenna array can be analyzed and figured out. To meet the requirements of high gain and broad bandwidth, the microstrip corporate matching network is implemented and connected with those series microstrip patch antenna array. To improve the ambiguity characterization of antenna array, the difference between the main lobe and the side lobe in the 2-D radiation pattern is expected to be larger than 10 dB. Different techniques are adopted to realize this goal. The inset feeding can increase 0.44 dB compared to the conventional edge feeding. Then, the difference of 11.6 dB can be obtained by adjusting the width of patch. Finally, it is shown that the antenna gain of 17.25 dBi and wide bandwidth of about 6.5 GHz (75.42GHz ~ 81 GHz) are achieved.