本論文提出三種頻率選擇面的設計，第一種為液晶頻率選擇面，採用雙層基板與三層金屬層加上一層液晶層的設計，金屬層設計使用耶路撒冷十字和帶有S形槽孔的矩形貼片。第二種為窄頻Pin Diode頻率選擇面設計，採用三層基板與四層金屬層的設計，金屬層設計分別是四個矩形貼片與十字型貼片，並透過對稱的圖案設計來達到極化不敏感特性。第三種為寬頻Pin Diode頻率選擇面設計，採用雙層基板與三層金屬層的設計，金屬層設計分別是上下矩形貼片和十字貼片，並採用類似的結構和較厚的基板以達到寬頻效果。
在效能方面，第一種設計為液晶頻率選擇面。其中心頻率約為4.85 GHz，在正入射時S21插入損失約為0.86dB，頻寬約為9.27%。並且在施加偏壓後其中心頻率可偏移至4.19GHz，損耗約為0.82dB，以S21的3dB為參考點，其頻寬約為8.35%，偏移量約為13.6%。當電磁波在0°~ 60°入射時，其最大的頻率偏差約為0.23%。第二種設計為窄頻Pin Diode-FSS，其在施加逆偏電壓後，在正入射時中心頻率約為4.85 GHz， S21插入損失約為1.64dB，以S21的3dB為參考點，其頻寬約為14.1%。而在施加順偏電壓後，其中心頻率可偏移至5.65GHz，損耗約為1.42dB，頻寬為14.1%，而偏移量則為16.4%。第三種設計為寬頻Pin Diode-FSS，在此設計中，施加逆偏電壓後其可涵蓋之頻率包含2.9GHz~5.9 GHz，且在4.85GHz時有最小插入損失約為0.28dB，以S21的3dB為參考點，其頻寬約為67.5%。並且在施加順偏電壓時其在0 GHz~10GHz的頻率範圍內有屏蔽效果，在5.85GHz時有S21最大插入損失約為13.4dB，其頻寬約為225%。
本論文透過實作來進行模擬效能之驗證，其中實作樣品大小約為12cm x 12 cm，由11x11個單元結構所組成，並將樣品放置於有10cm x 10cm開孔的防繞射板之中以防止電磁波繞射，量測時於無反射實驗室進行量測，其中發射天線距離滿足遠場條件，量測結果中顯示電磁波在TE極化正入射時，當施加逆偏電壓後，在4.85GHz時有S21插入損失最小約為0.3dB，頻寬約為67.3%，當施加順偏電壓後，在4.85GHz時有S21插入損失最小約為13.5dB。電磁波在TM極化正入射時，當施加逆偏電壓後，在4.85GHz時有S21插入損失最小約為0.3dB，頻寬約為67.2%，當施加順偏電壓後在4.85GHz時有S21插入損失最小約為16.8dB。

This thesis proposes three frequency selective surface (FSS) designs. The first design is a liquid crystal frequency selective surface (LC-FSS), which adopts a design with two substrates, three layers of metal, and one layer of LC. The metal layers are composed of one Jerusalem Cross and two rectangular patches with S-shaped slots. The second design is a narrow-bandwidth Pin Diode-FSS, which adopts a design with three substrates and four metal layers. The metal layers are composed of four rectangular patches, one square patch, and one cross-shaped patch. This design uses symmetric patterns to achieve polarization insensitivity. The third design is a wide-bandwidth Pin Diode-FSS, which adopts a design with two substrates and three metal layers. The metal layers are composed of two rectangular patches and one cross patch. This design uses similar structures but with thicker substrates to achieve the wide-bandwidth effect.
From the simulation results, the LC-FSS has a center frequency of about 4.85 GHz before applying a voltage. When electromagnetic (EM) waves are incident at 0 degree, the insertion loss of S21 is about 0.82 dB, and its bandwidth is about 9.27%. After applying a voltage, the center frequency has been shifted to 4.19 GHz. The insertion loss of S21 is about 0.86 dB, and its bandwidth is about 8.35%. The frequency tunability is about 13.6%. The second design is a narrow-bandwidth Pin Diode-FSS. In this design, when a reverse bias voltage has been applied and EM waves are incident at 0°, the center frequency is about 4.85 GHz with an insertion loss of 1.64 dB, and its bandwidth is approximately 14.1%. When a forward bias voltage has been applied, the center frequency has been shifted to 5.65 GHz with an insertion loss of 1.42 dB. The bandwidth is 14.1%, and the frequency tunability is about 16.4%. The third design is a broad-bandwidth Pin Diode-FSS. In this design, when a reverse bias voltage has been applied and EM waves are incident at 0°, its bandwidth is approximately between 2.9 GHz and 5.9 GHz, about 67.5% of the center frequency. The minimum insertion loss of S21 is about 0.28 dB at 4.85GHz. After applying a forward bias voltage, a shielding effect has also resulted between 0 GHz to 10 GHz. The minimum insertion loss of S21 is about 13.5 dB at 4.85GHz, and the shielding bandwidth is about 225%.
The designs reported in this thesis have also been experimentally evaluated through a prototype implementation. The size of the prototype is approximately 12cm x 12 cm, composed of 11x11 unit cells, and the prototype was placed in an anti-diffraction plate to prevent EM waves diffraction. The measurement was performed in the anechoic chamber. The transmitting antenna distance satisfies the far field conditions, ensuring the incident wave remains a plane wave. From the measurement, when a reverse bias voltage has been applied and EM waves with TE polarization are incident at 0°, the minimum insertion loss of S21 is about 0.3 dB at 4.85GHz, and the bandwidth is about 67.3% of the center frequency. When a forward bias voltage has been applied, the minimum insertion loss of S21 is about 13.5 dB at 4.85GHz.
When a reverse bias voltage has been applied and EM waves with TM polarization are incident at 0°, the minimum insertion loss of S21 is about 0.3 dB at 4.85GHz, and the bandwidth is about 67.2% of the center frequency. When a forward bias voltage has been applied, the minimum insertion loss of S21 is about 16.8 dB at 4.85GHz.

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