[[alternative]]Broadband Circularly Polarized Microstrip Antenna with Two Partially Shorted Walls

碩士電信工程研究所[[abstract]]本篇論文主要提出一個新穎的圓極化天線設計及其特性分析與研究；利用短路牆天線的優點：尺寸小、結構簡單且成本低，設計出寬頻圓極化部份接地微帶天線並以軟體模擬其特性分析。在寬頻圓極化部份接地微天線的設計中，將天線尺寸設計在1.8 GHz的頻段。此外，在天線的設計上為了達到寬頻的效果，本論文提出使用L型探針饋入端，在結構中利用矩形金屬片與銅柱形成L型探針饋入端來激發天線，以空氣為其介電基質，高度增加會使銅柱產生電感性，藉由調整矩形金屬片長度大小，其電容性可以有效的抑制銅柱所產生的寄生電感效應，控制天線的阻抗匹配達到寬頻的效果。阻抗頻寬的範圍1.62 GHz~2.47 GHz (約為41.6 %)，圓極化頻寬範圍約為1.55 GHz~2.07 GHz (約為28.73 %)，顯示所設計之微帶天線具可行性及實用性。[[abstract]]This paper proposes a new design for a circularly polarized microstrip antenna and analyzes its characteristics. Using the advantages of a shorting wall antenna, such as simple structure, small volume, and low cost, this paper designs a broadband, partially shorted, microstrip antenna with circular polarization. Software simulations reveal its characteristics. Two mechanisms in the antenna structure were able to excite the circularly polarized mode, and the antenna dimension was designed to operate in the 1.80 GHz band. Furthermore, to achieve the broadband effect, this study proposes the use of an L-probe feed to excite the antenna. This L-probe feed consists of a rectangular metal strip and a copper cylinder. The air dielectric served as a substrate, and the copper cylinder produced inductance as the structure height increased. Adjusting the length of the rectangular metal strip effectively alleviated the parasitic inductance effect of the copper cylinder. This design made it possible to control the impedance matching of the antenna and achieve broadband effects. The impedance bandwidth ranged from 1.62 GHz to 2.47 GHz (10 dB impedance bandwidth of about 41.6 %), and the circularly polarized bandwidth ranged from 1.55 GHz to 2.07 GHz (3 dB axial ratio bandwidth of about 28.73 %), showing the feasibility of the proposed microstrip antenna