隨著無線通訊技術的快速發展，無線通訊應用也越來越廣泛。為了兼容多個通訊系統的標準，對於雙頻或是多頻天線之需求也與日俱增。而傳統的多頻天線通常以分集或是植入槽孔的設計架構，容易有體積大、占空間的問題。 本研究以全平面式的結構與直接饋入的方式來設計天線，使其與基板較易整合，採用厚0.8mm的FR4基板，以相對介電係數(Relative Permittivity)為4.4，Dielectric Loss Tangent為0.02，來進行模擬並和實驗相驗證，設計可達到GPS、ISM、WLAN與GPS、(DCS/PCS)或(PCS/UMTS)、WLAN(5.8GHz頻段)的三種多頻天線架構。 首先以操作在1/4波長的平面單極天線作為天線的初始結構探討，為了進一步縮小天線的尺寸，吾人深入比較平面倒L型天線與平面倒F型天線的特性，並且以倒F天線的架構為基礎下，引進了具有多頻模態的整合型天線結構。為了要設計出符合無線通信系統的多頻段天線，除了利用一適當彎折的迴路天線來調整模態頻率比，滿足多頻操作的需求外，更進一步結合激發模態相近的倒L型天線與加入接地面的寄生結構來調整阻抗匹配達成增加頻寬的目的。 一些天線原型的實作量測結果與模擬皆非常相近，頻寬方面，分別可使低頻的(DCS/PCS)及(PCS/UMTS)頻帶由原頻寬比為6.64%增加至19.58%及20.37%；高頻WLAN頻帶則最多可由原來的2.06%增加至18.38%。輻射場形的部分，實測結果顯示其H-plane(XZ-plane)在各個共振頻率點上均能有不錯的全方向(Omni-Directional)輻射場型特性。 With the rapid development of wireless communication technique, there are continuous needs for dual-band/multi-band antennas to fulfill the application for various communication systems. The conventional multi-band antennas are usually designed through diversity structure or slot loading. But it usually ends up with relatively large volume. In this research, three full planer antennas are proposed for GPS、ISM、WLAN and GPS、(DCS/PCS) or (PCS/UMTS)、WLAN(5.8GHz) applications, respectively. These antennas are fed directly by a 50Ω coaxial line and fabricated on the FR4 substrate of thickness 0.8mm, whose relative permittivity is 4.4 and loss tangent is 0.02. At the beginning, we consider a quarter-wavelength planar monopole antenna structure. To reduce the antenna size, a combo antenna with multi-mode is introduced after the investigation of the characteristics of planar inverted L/F antennas. Meanwhile, a meander loop antenna is proposed to control the frequency ratio of the multiple resonant modes. In order to achieve good impedance matching, and to broaden the bandwidth, the meander loop antenna is combined with the inverted L antenna and an parasitic stub on the ground. The proposed antennas are carefully studied and experimentally verified. The lower band bandwidth in (DCS/PCS) and (PCS/UMTS) is improved from 6.64% to 19.58% and 20.37%, respectively; while, the higher band bandwidth in WLAN is improved from 2.06% to 18.38%. Moreover, the radiation patterns exhibit omni-directional characteristics in H plane (x-z plane) for all resonant frequencies.
