[[alternative]]A Study of a Circular Waveguide-Fed Microstrip Patch Antenna

碩士電子工程學系[[abstract]]本論文旨在探討嶄新結構之圓柱波導管饋微帶天線之特性，以HFSS模擬軟體模擬所設計之圓柱波導管饋微帶天線之電氣特性，並以SMA接頭置於圓柱波導管之位置距管末端短路面適當距離，使得到最佳之傳輸效果與以SMA接頭的阻抗匹配。其次尋找耦合槽縫之最佳尺寸，並由軟體計算之結果找尋金屬貼片天線之尺寸。接著測試不同介質材料以選擇可用支撐微帶天線的材料，藉以了解圓柱波導管與微帶天線之間透過狹槽以電場耦合方式激發微帶天線之饋線結構，探討不同厚度支撐微帶天線的材料間之變，並以實驗量測來驗證天線設計之正確尺寸。另於論文中呈現有關天線之輻射場形與頻寬、天線增益及共振模態、電流分佈等現象。 本研究探討嶄新圓柱波導管饋微帶天線，並以HFSS模擬軟體與實驗結果做比較以求驗證，預期本研究之結果可供日後研究者作為參考。[[abstract]]In this thesis, the structure of a microstrip patch antenna fed by a circular waveguide is studied. The waveguide is excited by an inserted cylindrical probe extended from an SMA connector. One end of the waveguide near to the SMA is sealed by inserting a movable copper rod which functions as a tuning-short. Moving the copper rod to an appropriate position can match the impedance of the circular waveguide to that of the SMA. The waveguide couples the energy to the microstrip patch through a narrow slot deposited on the open end of the waveguide. The metal plate surrounding the slot together with the waveguide flange serves as the ground plane for the microstriop patch antenna structure. The foam substrate of various thickness is laid on the ground plane to support the radiating patch. Extensive experiments have been carried out in this study to find the accurate dimensions of the antenna structure. The commercial software package ‘HFSS’ is used to simulate the antenna performance before the experiments. The current distributions of the patch at resonant frequencies are also computed by the ‘HFSS’. The characteristics of the proposed antenna, such as operating bands, bandwidths, far-field patterns, and antenna gains, are given in this thesis. It is believed that the proposed antenna structure with extremely low transmission losses is very suitable in millimeter and even in submillimeter systems