摘要或動機

The feasibility of new design approach for dual-band antenna array using genetic algorithm is demonstrated in this study. In the past year, one dual-band printed-strip dipole antenna, which operates at 0.9/1.8 GHz, had been implemented in the laboratory and leads to a satisfactory performance. However, the antenna element is suitable for application at base-station rather than handset. Conventional antennas suitable for base-station application are arrays, which consist of antenna elements and at least one feed network. Feed networks for antenna arrays are usually designed to operate at single-band capability, and therefore, it requires two feed networks for a conventional dual-band antenna array. Nevertheless, a dual-band antenna array fed by signal feed network is feasible in our study. To begin with, a full-wave solver ID3D is applied to evaluate the impedance matrix of antenna array with eight elements. Then, the antenna array is modeled as a cascaded equivalent transmission line such that the genetic algorithm could network of dual-band antenna array and yields a seven-section design, which meets the specification of base-station antennas.在過去的一年裡，本人曾製作過具有雙頻效果的雙面印刷偶極天線，並得到不錯的量測結果。由於此天線單元於實際應用上適於基地台天線陣列之設計，所以本研究著眼於天線陣列的設計。傳統上天線陣列的結構包含了兩個部分，分別是天線單元以及饋入電路。目前基地台所使用的大多都是單頻天線陣列，在雙頻天線陣列部分，通常需要兩個饋入電路分別對不同頻帶作訊號的饋入；因此，我們希望能實現使用單一饋入電路製成雙頻天線陣列的想法。本研究中，我們利用之前所做出來的天線單元來合成陣列，並希望此陣列在0.9HGz和1.8GHz兩個頻段都能產生良好的共振效果。我們利用電磁模擬軟體IE3D估算具有八個天線單元的天線陣列阻抗陣列後，再將此天線陣列轉換成串接式等效傳輸線電路。借由基因演算法(genetic algorithm)對此電路做最佳化，我們可以求得饋入電路各段傳輸線的尺寸。由此研究發現，我們的方法應用於單一饋入電路之雙頻天線陣列的設計是可行的，而此電路的模擬結果亦符合基地台天線陣列的規格。