本論文提出了一套將線性極化轉圓形極化的雙頻圓極化頻率選擇面極化器設計方法，該設計方法依循著頻率選擇面的等效電路設計。論文中雙頻圓極化器設計過程中結合濾波器設計觀念，以等效電路法來合成出雙頻頻率選擇面濾波器適合的電路，而在等效電路設計上擁有相當大的自由度，包含中心頻率、頻寬、基板選用…等，可依照設計者需求自由決定，並且在電路設計階段就能以等效電路預測雙頻圓極化器的軸比特性。在等效電路建立完成之後，以雙層複合型頻率選擇面設計雙頻圓極化器，其複合結構包含耶路撒冷槽孔與四組一字型槽孔，論文中也以全波模擬軟體與實驗來驗證設計理論。本論文製作之雙頻圓極化器量測結果所涵蓋的3dB圓極化頻帶為8.55 GHz到9.25 GHz與11.7 GHz到12.4 GHz，相對於兩組設計之中心頻率9 GHz與12 GHz，其3 dB軸比頻寬分別為7.8 %與5.8 %，且全波模擬與量測結果有良好的吻合度。本論文所設計完成的雙頻圓極化器可應用於X頻段的衛星通訊系統。 In the thesis, a novel design of dual-band circularly polarized polarizer which can convert linear polarization to circular polarization will be present. The frequency selective surface (FSS) design procedure is based on filter synthesizing equivalent circuit. Filter synthesizing method provides design freedom, including the center frequency, band width, substrate selection and so on. A second order Butterworth dual-band filter design procedure is applied for synthesis of dual-band circularly polarized polarizer. Base on the second order Butterworth dual-band equivalent circuit model, a simple composite unit cell including Jerusalem cross shaped slot and four straight slots are used to realize circularly polarized FSS. The validity of the procedure is verified using full-wave EM simulations and experimental characterization of a fabricated prototype of the proposed dual-band circularly polarized polarizer. The measured 3-dB axial ratio (AR) bandwidth of the proposed dual-band circularly polarized polarizer can cover 8.55 to 9.25 GHz (7.8% with respect to 9 GHz) and 11.7 to 12.4 GHz (5.8% with respect to 12 GHz). The proposed dual-band circularly polarized polarizer can be used in X-band satellite communications systems.
