印刷式毫米波圓極化空腔共振天線與陣列之研製

Abstract

在本論文，我們設計具有高增益及圓極化特性的空腔共振天線，其使用多層印刷電路板製作，並應用在毫米波頻段。空腔共振天線的架構由一層部分反射面和一層金屬接地面組成空腔，使波在空腔內來回共振以達到高增益之天線特性。本論文的天線架構，由重複四組饋入結構做順序旋轉排列，並接上順序相位電路去激發以產生圓極化。完成單一天線的設計後，我們在天線模組邊緣加上通孔排列成金屬壁，藉此增加單一天線的增益，並且減少天線模組之間的干擾。在組成陣列天線時，我們再次使用順序旋轉技術，使圓極化之長短軸比頻寬及阻抗頻寬同時增加。本論文所完成之天線效能為：單一天線的圓極化之長短軸比頻寬為1 %及阻抗頻寬為3.9 %，陣列天線的長短軸比例頻寬為8 %及阻抗頻寬為19 %；操作在29.1 GHz頻率下，天線正向輻射增益可達18.5 dBic，而２×２陣列天線之正向輻射增益可達22.3 dBic。

In this thesis, we propose a cavity resonant antenna (CRA) with high gain and circular polarization for millimeter wave applications. The presented CRA consists of a partially reflecting surface (PRS), a metallic ground plane, and a predesignated feeding structure in the cavity, all configured into a solid multi-layered printed circuit board (PCB). Through circuit loaded feeding structure, the excited EM waves bounce back and forth within the cavity and achieve the directive patterns. First, we arranged four symmetric feeding structures in sequential rotation and connected them to four sequential phased lumped port to verify the design concept of circular polarization (CP). Second, we designed a correspondent sequential phased 4-port power divider circuitry and connected to the predesignated feeding structures to realize the CP operation. Additionally, we employed a metallic wall with the plated through hole (PTH) surroundings the edges of the CRA unit module. Advantages of using the surrounding metallic wall may increase the antenna gain and suppress the coupling between the module elements in array. When designing the 2x2 array, we utilized the sequential rotation technique again to improve the axial ratio bandwidth and the impedance bandwidth of the entire array. The overall performances of the developed antennas are: the axial ratio bandwidth of 1 % and impedance bandwidth of 3.9 % for the single element; and the axial ratio bandwidth of 8% and impedance bandwidth of 19 % for array. For the antenna gain at broadside, the presented antenna achieved an 18.5 dBic for the single element and a 22.3 dBic for the 2x2 arrays.