適用於不同接地面積之可調式2.45GHz微型化天線

Abstract

本論文提出適用於不同接地面大小之頻率及阻抗可調式微型化天線，操作頻率為2.4 GHz ~ 2.5 GHz的Wi-Fi頻段，輻射效率為30% ~ 40%，天線所放置的基板大小為40 mm x 20 mm x 1 mm，實際所佔用的體積為11.3 mm x 9.5 mm x 1.98 mm，相對於中心頻2.45 GHz，亦即0.092λx 0.078λx 0.016λ。在設計上，結合了平面型倒F天線以及槽孔天線，並利用疊構的設計，可有效減少天線的占用面積，且不受內部IC及Balun等元件走線的影響。此外，當此天線應用於不同的接地面大小或是不同的環境，而造成中心頻率偏移或是阻抗不匹配時，可使用外部被動元件調整此天線的輸入阻抗以及共振頻率，以維持相同的天線響應，亦提供使用者在應用此產品時的自由度。 本論文也提出頻率偏移抑制的設計，當天線所放置的接地面大小改變或是放置的位置不同時，會使天線的操作頻率偏移，透過此設計可有效抑制電流的方向，降低電流受接地面大小或放置位置的影響，將頻率的最大偏移量控制在50 MHz以內，並藉由外部被動元件將操作頻率調整至中心頻率的位置。

In this thesis, the frequency and impedance tunable miniaturized antenna for different ground planes is proposed. The operating frequency is 2.4 GHz to 2.5 GHz in Wi-Fi band and the radiation efficiency is 30% ~ 40%. The size of substrate is 40 mm x 20 mm x 1 mm, and the occupied area of the antenna is 11.3 mm x 9.5 mm x 1.98 mm. The combination of the planar inverted-F antenna and the slot antenna is designed to reduce the occupied area of the antenna and the performance of the antenna is not affected by the internal components such as IC, Balun and other components. In addition, when the antenna is used in the different ground plane sizes or different environments, the center frequency will shift or the input impedance will be mismatched. An external passive element can be added to improve the performance of the antenna. In this thesis, the design of frequency offset suppression is also proposed. When the antenna is placed in the different ground plane sizes, the operating frequency of the antenna will shift. By this design, the current direction can be effectively suppressed. The maximum offset of the resonant frequency can be controlled within 50 MHz, and the operating frequency can be adjusted to the location of the center frequency of 2.45 GHz by adding the external passive components.