本論文的研究在於設計一具圓極化雙頻共平面波導饋入之槽孔天線，利用共平面波導的饋入結構，與L形槽孔天線共同製作在基板的同一平面上，可以簡化整個設計的流程與實作上對位的問題。在50 Ω饋入線的末端加入突出殘段以達到較佳的阻抗匹配條件，藉由縮短L形槽孔其中一個天線臂的長度，產生相位差90度之兩個正交電場，激發出圓極化電磁波。此外，在已調整過尺寸之L形槽孔另一個天線臂末端，增加一指形狹縫，以及修改接地面的尺寸大小，使得阻抗頻寬有顯著的增加。所提出的雙頻L形槽孔天線，第一個頻帶以2.78 GHz為中心頻率，阻抗頻寬約為77.3 %，另一個以5.57 GHz為中心頻率的頻帶，阻抗頻寬約為23.7 %，同時，軸比頻寬也可達到15.1 %（最佳化可達22.0 %），天線可以應用在許多行動通訊系統，如DCS、PCS、WCDMA、SDAR、WLANs、LTE以及Hiper-LAN。

The study of the thesis is to present a design procedure for a dual-band CPW-fed linearly and circularly polarized (CP) antenna based on the L-shaped slot antenna. The slot antenna and the feeding structure are fabricated on the same plane of the substrate so that circuit processes and position alignment can be simplified. By shortening the length of one arm of the L-slot, an additional mode with two orthogonal electrical fields with a phase difference of 90 degree is excited, so that the circularly polarized wave can also be excited. The enhancement of the resonant bandwidth is achieved by utilizing a stub-protruded feedline, adding one finger slit at the other arm slot, and tuning the dimension of the ground plane. Through modification with antennas of various geometrical parameters, the proposed antenna exhibits a wide bandwidth in the desired frequency bands, which has one bandwidth of 77.3 % at 2.78 GHz and the other one of 23.7 % at 5.57 GHz for an input reflection coefficient of less than -10 dB. Meanwhile, the antenna has a 3-dB axial ratio (AR) bandwidth of 15.1 %. A bandwidth of 22.0 % (2.23-2.78 GHz) is achieved with an axial ratio < 3 dB for the optimized case.

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