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    题名: 應用於藍芽/無線區域網路的縮小化雙頻PIFA天線
    其它题名: A dual-band reduced-size PIFA antenna for BT/WLAN application
    作者: 劉吉祥;Liu, Chi-hsiang
    贡献者: 淡江大學電機工程學系碩士在職專班
    李慶烈;Li, Ching-lieh
    关键词: 平面倒F天線;無線網路;藍芽;Pifa antenna;WiFi;Bluetooth
    日期: 2009
    上传时间: 2010-01-11 07:12:48 (UTC+8)
    摘要: 本論文設計一個PIFA天線,目的在將天線元件縮小化,應用於802.11a/b/g無線區域網路及802.15藍芽標準的雙頻(2.402-2.483GHz、5.15-5.825GHz) 天線,以支援行動電話及其相關的小型行動裝置或滿足其它ISM頻段產品的需求。
    此天線的輻射本體為立體倒F型的PIFA天線,透過對PIFA天線的立體化將天線縮小於印刷電路板(PCB)的板邊附近,其目的是讓輻射天線能遠離金屬元件(如speaker、camera..等)的干擾,讓天線附近區域能夠淨空並且將能量輻射出去。所以本論文的天線本體也置放於PCB的板邊,以符合一般商用產品的實際使用方式。另外,使用立體PIFA天線的優點包括比較不佔PCB的空間,雖然此一設計的實作上需要利用到機械加工,但因此天線的最小尺寸是0.2mm,不需要使用精密的機械來加工。又天線本體採用便宜的馬口鐵製作,整個天線的製作並不需要花很多成本且能達到節省空間的目的。
    為設計立體倒F型PIFA天線,首先將輻射本體藉由短路接腳而引進電感,並且將平面天線挖出很多的槽孔(slot)形成曲折(meander)的方式,讓天線能操作在四分之一波長,本論文並探討槽孔參數對於天線特性的影響。
    此外,吾人採用缺陷型接地結構(DGS)的方法來改善2.4GHz和5GHz的頻寬,特別是2.4GHz處頻寬的增加,由於PIFA天線的缺點是當其操作頻率越低則頻寬愈窄,一般增加頻寬的常用方式包括增加天線的高度,但這和縮小化的目標矛盾。本論文改採用DGS的方法,及在天線本體正下方的FR4接地面,將地挖除2.5X11mm2的面積,其結果使得低頻2.4GHz頻段增加了22MHz的頻寬,高頻的部份則增加了126Mhz的頻寬(S11<-10dB)。
    我們也針對本天線的設計進行一些參數變化的完整探討,例如,天線短路接腳大小與距離、DGS高度與大小等,最後將天線縮小化至11X6X4mm3的體積,其頻寬和效能都能達到符合期望的要求。
    This thesis is to design a miniature dual band antenna for 802.11 a/b/g wireless LAN (2.402 GHz ~ 2.483 GHz and 5.15 GHz ~ 5.825 GHz) and 802.15 Bluetooth (2.402 GHz ~ 2.483 GHz) by using the PIFA structure. It can be applied for the products of mobile phones, miniature portable devices and other products with ISM band.

    The proposed antenna is designed by using a three-dimensional inverted-F antenna structure. The antenna volume can be reduced by arranging the antenna close to the corner of printed circuit board, which keeps antenna away from any metal component (such as speaker, camera … etc.). Because of this structure, there is a clear area for the proposed antenna and antenna radiation can go out. To mimic this in this thesis, the antenna is placed at the corner of the PCB board similar as the actual commercial products in general.

    The advantage of the three dimensional PIFA antenna occupies less PCB space usually. Although the proposed PIFA antenna needs machining to produce, the smallest dimension is about 0.2 mm only , thus it doesn’t need to use sophisticated machinery. In addition, the proposed antenna body uses cheap tinplate for production, which cost little .

    In order to design a three-dimensional planar inverted-F antenna of size 11X6X4 mm3 the rectangular patch is short circuited first by a shorting pin. Then several slits are introduced on the rectangular patch to form a meandering structure, of which the length is about one-quarter for the lowest resonant frequency. The effects of these slit parameters to the antenna characteristics are also studied.

    In addition, the idea of defected ground is employed to improve the bandwidth, especially 2.4G band. One of the disadvantages of the PIFA antennas is the small bandwith for the low band as compared with the corresponding monopole antenna. The initial PIFA design faces the issue that the frequency bandwidth of low band is not wide enough. Although there are several ways to further improve the bandwidth, such as increasing the height of the antenna, those that would increase the volume of the antenna is not considered suited for miniature devices. In this thesis, we uses defected ground by excavating an area of 2.5X11mm2 out of the FR4 board ground right under the antenna. The results show that the bandwidth improvement~ 22MHz is achieved at the low band, 2.4GHz, and ~126MHz for the high band, 5.8G ( |S11|<-10dB).

    The effects of several parameters of the PIFA antenna structure are investigated, which include the width and distance of the short-circuiting pin, the size of the defected ground, etc. Based on these analyses, the miniature PIFA antenna is successfully designed with the volume of the antenna limited to 11X6X4mm3 and its bandwidth and performance can meet the requirements of the expectations.
    显示于类别:[電機工程學系暨研究所] 學位論文

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