應用於無線通訊之非對稱共面波導饋入式小型天線設計

Design of Miniaturized Asymmetrical CPW-fed Antennas for Wireless Communication

劉鴻鈞(Hong-Jun Liu)

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2007年)

摘要

通訊最前端且影響通訊品質最重要的關鍵元件─天線，在現今行動通訊產品訴求著輕、薄、短 、小等因素下，天線外型的設計以小型化為趨勢。而平面微帶天線結構因具有體積小、質量輕 、製造方便、成本低廉、低姿勢、低交叉極化輻射場型、且易與單晶微波積體電路整合等優點 ，遂為廣泛採用的天線設計結構。 本論文將以共平面波導饋入方式與非對稱接地面設計結構，於 FR-4 玻璃纖維板上設計出兼具 多頻操作能力，可應用於無線區域網路的小型平面微帶天線，並探討共振頻率下饋入線與非對 稱接地面之間的電磁耦合效應。 設計中以一非對稱接地面共面波導饋入天線作為雛形，並透過調整饋入線與倒 「L」形接地面 長度使得該天線可操作於5.2 或5.8 GHz 無線區域網路頻帶上，並分析金屬輻射體間之電磁耦 合對共振頻率點的影響。再者，延伸天線之上端金屬輻射體尺寸，並於所延伸之金屬輻射體上 ，以嵌入槽孔的方式進行研究，發現在適當地選擇槽孔深度與位置時，可設計出一非對稱接地 面型共面波導饋入式三頻天線，其操作頻帶包含2.4 GHz/5GHz無線區域網路頻段與C 頻段之衛 星通訊頻段。最後，利用曲繞饋入線方式來縮小天線尺寸並提升在5.2 GHz 頻段操作時的頻寬 。此非對稱接地面型三頻曲繞式小型共平面波導饋天線長寬尺寸僅為9×17 mm2，且於2.44、 5.07 與7.17 GHz 之−10 dB 阻抗頻寬比分別達14.3% 、16.3% 與19.8% ，可應用於2.4 GHz 無線區域網路/藍芽/射頻標籤、5.2 GHz 無線區域網路與C 頻段衛星通訊等。

並列摘要

Antenna which is put at the front and always significantly affects the communicationquality has become a most important element for a communication system. For potential usein a modern mobile communication system, the trend of antenna design is focused on thecritics of light weight, planar profile and compact size. Therefore, the planar microstrip antenna is the most suitable prototype for wireless communication due to its wide bandwidth, good impedance matching, simple structure of a single metallic layer, no soldering point, and easy integration with system circuit etc.
In this thesis, the structure of a coplanar-waveguide (CPW) feeder with two asymmetrical grounds, printed on an FR4 substrate, was utilized to design a multi-band compact antenna for wireless local area network (WLAN) application. Also, the electromagnetic coupling effects on resonant frequencies between the feeding line and the asymmetrical grounds were studied.
The design based on a CPW-fed antenna with an asymmetrical ground structure hasfirstly been studied to achieve a resonant mode suitable for 5.2 GHz or 5.8 GHz WLAN use by adjusting lengths of the feed line and the inverted-L shaped ground. The electromagnetic coupling effect on resonant frequencies between the radiating elements has been investigated,too. Thereafter, by way of properly extending the loaded radiating patch of the antenna and embedding a slot into the patch, the proposed antenna can produce triple-band resonance covering the 2.4/5 GHz WLAN bands and the C-band satellite communication. Finally, the technology of meander line is applied to miniaturize the antenna size and increase the impedance bandwidth in 5.2 GHz band. The modified antenna is only 9×17 mm2 and can excite resonant modes at 2.44, 5.07, and 7.17 GHz bands with measured -10 dB impedance bandwidths of 14.3 %, 16.3%, and 19.8 %, respectively. The antenna is very compact and able to cover the 2.4/5.2 GHz WLAN as well as the satellite communication operating at C band.

參考文獻

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