- 學位論文
應用於衛星訊號接收之車用多模態圓極化接收天線設計
Circularly polarized Multi-modal Antenna Design for Mobile Reception of Satellite Signals in Automotive Applications
摘要
本論文目的為設計車用天線結構，應用於接收歐洲ONDAS衛星廣播系統訊號之用，其頻段使用範圍為S頻段(2170MHz~2200MHz)，對於幅員遼闊的國家來講，為求衛星訊號覆蓋率可達整個歐洲，因此衛星廣播系統通常會嚴格規範天線在特定仰角範圍內的平均增益值大小，以本計畫所針對ONDAS衛星廣播系統為基準，分別在仰角90度為4dBic，仰角75~45度為5dBic，而仰角30度則為3dBic，同時天線亦須符合實際車用測試規範於一公尺參考地平面上進行設計。針對歐洲ONDAS衛星廣播系統的需求進行車用天線設計，主輻射體為具圓極化特性的微帶天線結構，採用多模態(TM)激發方式，分別為低階模態(TM10、TM01)與高階模態(TM31)，利用低階模態輻射場型貢獻於高仰角部分並且加入方向導引器(Director)來提升高仰角覆蓋率；高階模態則是針對低仰角輻射方向，在饋入位置上採用方向耦合器產生相同振幅以及90度相位差，並探討天線與一公尺地平面之間的距離對於增益值影響，經由模擬驗證及實際製作量測，我們所提之天線結構能符合ONDAS衛星廣播系統的規範，並在仰角90~30度之間具備了類均向性的輻射場型，可達到穩定的衛星訊號接收，並具實際產業應用上的價值。
並列摘要
The purpose of this paper is design of innovative antenna structure for reception of digital radio signals of ONDAS satellite broadcasting system within the S-band(2.17 GHz~2.2GHz) in automotive applications, in order to achieve the reception of satellite signal which can cover the whole of Europe, the specifications and targets desired of the antenna is always more stringent than another satellite broadcasting system at specific elevation angles, the minimum average gain of +4 dBic is required at elevation angle 900, +5 dBic is required at elevation angle between 450-750 and +3 dBic is required at elevation angle 300, and the antenna should be designed above the 1-m ground plane basis to the vehicle specification testing. The proposed antenna is a circularly polarized microstrip antenna structure used by multi-modal excitation where fundamental modes and higher order modes, respectively. The antenna radiation pattern of fundamental modes is contribute to high elevation angle and we use a director for promoting high elevation angle coverage, the higher order modes is contribute to low elevation angle, and the antenna fed by directional coupled circuit to generate equal magnitude and phase difference 90deg, where mounted on the center of 1-m ground plane, the simulated results show a good agreement with the measured results to verify the proposed antenna can meet the specifications of ONDAS satellite broadcasting system, and the antenna has a quasi-isotropic radiation pattern at elevation angle between 300-900. Hence, the stable satellite signal reception can be achieved and the proposed antenna structure is suitable for practical application.