超寬頻及高整合模組應用之縮小化天線

Abstract

本論文旨在縮小化天線之研究，包含超寬頻天線以及高整合度模組兩方面的應用。本研究所提出的天線設計，均具備結構簡單、製作與積體化容易、成本低廉，以及良好的阻抗匹配與穩定的輻射場型等特性。 首先，就超寬頻應用方面，本論文提出一種具有二次多項式曲線之單極超寬頻天線設計。利用所提出的二次多項式方程式，並適當地選擇相關變數達成超寬頻天線的設計。此外，為了達成具有頻帶截止的功能，我們採用並聯LC電路架構，藉由調整電路中電感與電容值，能得到適當的截止頻率與截止頻寬。由實驗量測結果顯示，具有頻帶截止功能之超寬頻天線，在截止頻帶內之平均天線增益與全頻帶超寬頻天線相比約小 -18 dBi，而截止頻帶外的增益與輻射場型則與全頻帶超寬頻天線相似。 再者，本論文提出一種架構簡單、小型化單極似之印刷式超寬頻天線設計。此天線係由一單極天線支段與一類傳輸線支段所組成，訊號由天線饋入端饋入後，先通過類傳輸線支段後進入單極天線支段。此一類傳輸線支段在不同操作頻段具有不同的功能，不僅能提供阻抗匹配之外，同時也可成為主要的輻射體，進而達成超寬頻的特性。 此外，一具有垂直於水平面的強電場且低側高之超寬頻天線設計，也於本論文中提出與研究。於接地面上內埋兩個L形狹縫，不僅能提供額外的共振頻率，更可改善輸入阻抗匹配，進而得到寬頻的天線特性。再者，由於天線饋入端與短路端之電流方向，在操作頻帶下均相同的緣故，因此本天線與其他一般印刷式天線相比，在水平切面上具有更強的垂直電流。至於周圍金屬物體對天線特性的影響，同樣也於本論文中討論，本天線與金屬平面近距離平行擺放時，仍然維持良好的輻射特性，並且天線高度僅為5mm。 最後，針對高整合模組應用方面，本研究提出一種一體成形並直接製作於電路屏蔽盒上之小型化系統封裝天線設計，其應用頻段為無線區域網路IEEE 802.11b/g。於本研究中，對於天線與內埋於電路屏蔽盒之射頻元件之間的耦合效應做相關討論，並且也將此系統封裝天線與無線區域網路之前端電路相整合，進行相關電路特性的量測之外，更進一步將此整合後的天線與無線區域網卡上的基頻電路相連接，其量測之EVM在操作頻段內均大於-30dB，具備相當良好的特性。同時也可由系統封裝天線之優異輻射特性，再次證實此設計實際應用於無線區域網路通訊之可行性。本天線尺寸僅為15 mm × 20 mm × 3.5 mm。

This dissertation is focused on the miniaturized antenna development for ultra-wideband (UWB) and high integration module applications. These antenna designs have the merits of simple in geometry, easy for manufacture and integration, low-cost, and exhibits a good impedance matching in addition to have stable radiation patterns over the bandwidths. Firstly, for UWB communication applications, a new binomial curved monopole UWB antenna is introduced. In this study, we propose a new edge curve, characterized by the binomial function and properly choose the parameters of the binomial function, for designing UWB antenna. Besides, to achieve the band notch function with a UWB antenna, the concept of the parallel LC circuit is applied. By adjusting the inductor and capacitor values, the suitable notch frequency and bandwidth can be achieved. The average gain is lower than -18 dBi in the stopband, while the patterns and the gains at frequencies other than in the stopband are similar to that of the antenna without the band-notched function. Secondly, a simple and compact monopole-like printed ultra-wideband antenna is presented. The antenna is composed of a monopole section and a quasi-transmission line section. The input signal from the feed line first passes through the line section then enters the monopole. The quasi-transmission line section provides different functions as the operating frequency changes. It serves not only as an impedance matching circuit but also a main radiator, which leads to the ultra-wideband performance of the antenna. Thirdly, a low-profile UWB antenna with strong vertically field has been proposed and investigated. Two L-shaped slits are embedded on the ground plane, which provide additional resonances and improve the input impedance matching thus wideband performance can be obtained. Besides, according to that the current direction on the feed and shorting strip are the same, hence, the proposed antenna has stronger vertical polarization field as compared to the conventional printed antenna in horizontal plane. Moreover, the metal body’s effect on the antenna performance also analyzed. The proposed antenna maintains good radiation characteristics while a metal plane is placed parallel under the antenna closely. The proposed antenna has a low-profile of 5 mm. Finally, a miniaturized antenna design, for the high integration module application has been proposed and demonstrated. This on-package planar inverted-F antenna (PIFA) made from a single folded metal plate and fabricate directly on the shielding package for IEEE 802.11b/g WLAN band applications. In this study, the coupling between the antenna and the RF component embedded inside the package is studied. Moreover, an on-package PIFA integrated with a WLAN front-end module (FEM) and a WLAN card containing the baseband/medium access control (MAC) circuitry is successfully implemented. The Error Vector Magnitude (EVM) in the operating band is better than -30 dB, indicating the good performance of the architecture. From the tested result, it seems that the on-package PIFA has good radiation characteristic and thus suitable for the WLAN communication applications. The prototype has a compact size of 15 mm × 20 mm × 3.5 mm.