Three Reconfigurable Slot Antennas Realized by Varactor Diodes

本論文提出以變容二極體實現三款可調式槽孔天線，此三款天線分別為頻率可調式、極化可調式，以及場型可調式天線。這些天線皆為槽孔天線，並且可應用適應各種通訊系統和環境。 首先本論文提出雙頻操作頻率可調式共面波導天線，其兩個共振頻率可分別由兩個變容二極體獨立控制，本論文提出此天線之等效電路模型並進行分析。 此外，亦使用雙饋入槽孔環形天線以及可調式電路來實現極化可調式天線。此可調式電路以變容二極體來達成相移器以及功率分配器的功用，因此，該天線極化可由左(右)手圓極化調整至任意軸比之左(右)手橢圓極化，再調整至線性極化。 最後，吾人以可調式電路和槽孔陣列實現一維與二維波束可調天線，其波束方向可調整在±20°內，並且旁辦位準可維持在-15 dB，其反射係數亦低於-10 dB。所有的模擬以及量測資料皆吻合並呈現於此論文中。In this thesis, three reconfigurable slot antennas are proposed using varactor diodes to respectively realize the frequency reconfiguration, polarization reconfiguration, and pattern reconfiguration. All the antennas are based on planar slot radiators, and these antennas can be applied and adapted to various communication systems and environments. To begin with, the frequency-reconfigurable coplanar waveguide (CPW) resonator antenna is proposed for dual-band operation. The two resonant frequencies can be determined by the two varactor diodes independently and respectively. The equivalent circuit model of the proposed frequency-tunable antenna is also presented and analyzed. Furthermore, a polarization-reconfigurable antenna is realized with a dual-feed slot loop antenna and our proposed reconfigurable circuit. The proposed circuit with varactor diodes serves as phase shifters and a power divider. As a result, the polarization can alter from left- (right-)handed circular to left- (right-)handed elliptical with arbitrary axial ratio to linear polarization. Finally, with the proposed circuits and simple slot array arrangement, one- and two-dimensional beam-steering antennas are implemented. The directions of main beams can be adjusted within ±20° from the broadside and the sidelobe levels remain below 15 dB. The reflection coefficients are below 10 dB. All the simulated and measured results are presented and reach a good agreement