卷期 : 42 / 3
出版年 : 2014/07/01
主動相列天線系統利用T/R模組中數位可調衰減器與移相器可以控制射頻固態放大器的功率分布,進而合成所需之遠場輻射場型。但若天線輻射元之主動元件發生老化或其他原因失效時,會造成不正確的陣列輻射場型,故天線輻射元的振幅和相位校正是非常重要的,尤其是低旁波束級相列天線陣列,所以在這種情況下,優先考慮近場量測。不過一旦在主動相列天線陣列系統於陣地佈置完成後,如有些T/R模組失效或是訊號相位及振幅設定不正確的話,該如何重新校正天線輻射元的振幅和相位是一個非常重要的問題。鑒於當T/R模組發生老化或其他原因失效時,無法即時回近場測試系統維修檢驗,本文提出一個陣列天線輻射元振幅與相位校正的方法,可以為每一個波束尋找到最佳的振幅和相位設定。文中首先簡要地介紹線性陣列天線的理論,其次,闡述利用參考天線相位調變的校正原理,並運用HFSS電磁模擬軟體驗證該方法之可行性。最後介紹應用參考天線相位調變自校法於主動相列天線陣列系統的設計範例。針對平面主動相列天線陣列系統每個row-beam上異常的T/R模組校準其振幅分布與相位差,經由參考天線相位調變調校後場型劣化情形可大幅改善,並回復最初-30dB低旁波束泰勒分布設計,經由分析驗證參考天線相位調變校正法是一個可以提供準確、簡單、低成本、易於實現在主動相列雷達的可行校正方式。For the experimental characterization of active phased array antennas, it has been shown much more elaborated test than that of conventional passive antennas. A number of additional tests are needed as a result of applying RF solid-state amplifiers in the T/R modules of active phased array antennas which generate the excitation of the antenna elements to synthesize the far-field radiation patterns in space domain. If the amplitude and phase of the excitations are not properly set, an incorrect radiation pattern of the array may result. Thus, the amplitude and phase settings alignment to the antenna elements is therefore very important, especially for the low side-lobes level requirement. Consequently, the near-field test range is generally preferred in this situation. However, once the events of some failed T/R modules or not properly phase setting were happened to the deployed active phased array antennas, how to perform the excitation coefficient re-calibrating procedure to the antenna elements is an importance issue since it is not possible to build a near-field test range in the ground-based area. In this report, a calibration procedure is proposed to align the excitation of the array antenna elements. These data can be used to find the optimum amplitude and phase settings for each scanning beam. First, the theory about linear arrays is briefly discussed. Second, the principles of the Phase Rotation Method (PRM) are described. The usage of proposed method is validated numerically based on the EM simulation using HFSS. Finally, an example applying the far-field PRM to a row-beam on the developed planar active phased array antenna is introduced in detail. De-embedded excitation coefficients corresponding to each sub-array of a row-beam on the planar active phased antenna are given to obtain radiation patterns with Taylor -30dB side-lobes distribution. The PRM -method is proved to be effective for far-field calibration of an active phased array system due to its accuracy, simplicity, cost-effectiveness, and easy to implement.
關鍵詞 : T/R模組(T/R Modules)、相列天線(Phased Array Antennas, PAA)、遠場(Far-Field)、近場(Near-Field)、參考天線相位調變校正法(Phase Rotation Method, PRM)、HFSS