本論文提出線性極化轉圓極化的頻率選擇面極化器之設計方法。將一個線性偏極化的天線置於適當的位置，當此天線輻射的電場穿透所設計的頻率選擇面時，使之能轉換為圓形偏極化的輻射遠場。頻率選擇面屬於微波被動電路，它在文獻中已有多樣的功能被提出。在本研究中，將頻率選擇面設計緊密地結合了微波電路與微波濾波器的設計觀念，提供了相當明確的設計流程。首先提出等效電路，再設計頻率選擇面的方式，此方法在相關文獻中是少見的。在論文中所提出的設計方式，提供了相當高的設計自由度，包含中心頻率、頻寬與基板的選用……等。頻率選擇面的實測結果在電路模擬已能夠被預估。本研究以簡單的十字型槽孔單元結構實現圓極化頻率選擇面，可應用在X頻段衛星傳訊系統。本論文所提出的雙層圓極化頻帶範圍涵蓋9.203 GHz到10.765 GHz，相對於中心頻率10 GHz的軸比頻寬(軸比值< 3 dB)達15.6%，並解決了文獻中透射式的頻率選擇面極化器，一半能量損耗的問題。模擬與量測結果在論文中均有詳細地分析與比較。The thesis presents a design method to realize frequency selective surfaces (FSS) polarizer which can convert linear polarization to circular polarization. Let a linearly-polarized antenna placed at the appropriate location to make the electric field of the antenna propagate through the designed FSS. The electric field can be converted into the one of circular polarization. FSSs are microwave passive circuits. A variety of designs have been proposed in the literature. In our study, how to design the FSS is based on the microwave filter design concept. Also, the clear design process is presented. The proposed FSS design integrates the microwave filter design concept closely. The equivalent circuit of the filter is first designed, and then the frequency selective surface is realized. The proposed method is not only rare in the literature, it also provides a very high-level design freedom, including the center frequency, bandwidth, substrate selection, and so on. Measured results of the FSS can be estimated by circuit simulator. In this study, a simple cross-shaped slot unit cell is used to realize circularly polarized FSS, which can be used in X-band satellite communications systems. The proposed dual-layer circularly polarized FSS covers 9.203 to 10.765 GHz. The 3-dB axial ratio bandwidth is up to 15.6% with the center frequency of 10 GHz .It also solves the penetration-type FSS polarizer’s 50% energy loss problem in literature. Simulated and measured results are analyzed and compared.
