穿戴式可彎折天線及平面式毫米波多極化陣列天線

Abstract

此論文分成兩大部分，第一個部分探討及研究用於人體的穿戴式天線設計方法，第二個部分則研究用於60 GHz 毫米波頻段的多極化天線及陣列的實現方法。在用於人體的天線設計當中，此研究提出了一款外型如OK繃、可彎折，且貼附於人體的天線設計，同時也探討人體組織對於天線特性的影響。在此設計中，我們提出了一種偏移式的天線饋入方法，藉由此方法可以激發狹長形天線的橫向共振模態(TM01 mode)。此外，此天線也利用虛接地的技巧將背面的金屬面與傳輸線的地線連接，讓天線得以平面化、不需要垂直連接或是灌孔的製程。如此一來，此設計方式非常適合可彎折的應用。另外藉由天線尾端延伸基板的特殊設計，此天線成功解決了平板天線在E-plane彎折時，天線增益下降，輻射場型朝背向輻射的問題。此天線結構簡單，平放置於人體體表間隔1毫米時，量測到的天線增益為2.01 dBi，輻射效率為41.7%，而模擬的SAR值為1.183 W/kg3，非常適合用於人體無線區域網路。而在第二部分毫米波多極化陣列天線當中，提出了幾款可於毫米波頻段實現多重極化切換的平面天線。此天線有四個輸入端口，各端口對應到不同的天線極化。因此藉由切換天線的饋入端口，即可於毫米波頻段實現極化切換的功能。另外也提出多極化天線操作在圓極化模態時，增加圓極化軸比頻寬的設計方式。而在多極化陣列天線的部分，我們提出了一款2×2的天線陣列，並可擴展至4×4的架構。此天線含有兩個輸入端口，透過改變兩輸入端口的相位差，此天線可以產生左手圓極化、右手圓極化，以及四種方向的線性極化。此2×2及4×4陣列天線所量測到的天線增益分別為12.03 dBi及16 dBi，成功的在60 GHz 毫米波頻段實現極化可切換的陣列天線。

This dissertation can be categorized into two parts; the first part is about the design and analysis for on-body antenna, and the second part studies the implementation of polarization diversity at 60 GHz and also the array design with polarization switchable characteristics. In the study of on-body antenna design, an adhesive-bandage like antenna which is able to be bent and be placed on human body tissue has been presented. An offset feeding method is proposed which can be used to excite transverse resonant mode (TM01 mode) on a long and thin patch. Also, the virtual ground method is applied in this design to virtually connect the metal conductor on the back side of the circuit board to the ground conductor of the feed line, no via or any vertical connection is required. Therefore, this design is very suitable for bendable applications. In addition, by a special design of the edge extension on the ground conductor, the problem in antenna gain degradation and the radiated power directed to the backside of the antenna when the patch antenna bent in E-plane can be solved. The achieved antenna gain is about 2.01 dBi and the measured radiation efficiency is 41.7% when the proposed antenna placed on the human body tissue and space by 1 mm. The calculated SAR is 1.183 W/kg3. The antenna configuration is simple, which is very suitable for wireless body area network. In the second part of this dissertation regarding the design of 60-GHz polarization diversity antenna, some designs which are planar and can realize polarization switchable characteristics at 60 GHz have been presented. These antennas have four input ports, and each port corresponds to different polarization. Therefore, polarizations of the millimeter wave antenna are possible to be changed by selecting various inputs. A four-port quadri-polarization diversity antenna design which can improve the axial-ratio bandwidth when it operates in circular polarized mode is also presented. For antenna array with polarization agile capability, a 2×2 array is proposed, and this design can be extended to a 4×4 configuration. These 60-GHz polarization switchable antenna array have two input ports, the polarization of which can be switched to right-hand circular polarization, left-hand circular polarization, or the linear polarization in four directions by controlling the phase difference of the two input ports. The measured antenna gain of the 2×2 and 4×4 polarization switchable antenna array is 12.03 dBi and 16 dBi, respectively, successfully demonstrate polarization switchable antenna array at 60 GHz.