寬頻平面式微波組件之設計-天線、Balun與濾波器

Design of Broadband Planar Microwave Components– Antenna, Balun and Filter

陳家賢(Chia-Hsien Chen)

指導教授 ： 毛紹綱

國立臺北科技大學/機電學院/電腦與通訊研究所/碩士(2006年)

https://doi.org/10.6841/NTUT.2006.00181

摘要

在本篇論文中分為三個主題，平面式饋入等角螺旋天線、寬頻的平面式Balun與三線耦合線分析、覆背式共面波導寬頻濾波器。並透過實驗與模擬結果來相印證。
我們使用微帶線結構饋入平面式等角螺旋天線，頻寬從2.8 GHz到17.1 GHz皆小於-10 dB，軸比頻寬從2.75 GHz到13.5 GHz皆大於3 dB，而天線增益除了在12 GHz上升至6.2 dBi，其餘在3.5 dBi左右，整體天線的面積降低，且經由微帶線饋入，克服了傳統使用同軸電纜饋入等角螺旋天線不易整合至平面印刷電路的缺點。最後設計的模擬結果和實驗量測結果得到一致性。我們利用共面波導結構來設計Balun，輸入特徵阻抗為50歐姆，輸出為100歐姆，背對背連接的頻寬從100 MHz到 4 GHz 皆大於-0.7 dB，整體結構大小僅 8 mm*20 mm。而藉由三線耦合線和雙線耦合線的理論分析，我們得到兩者結構的正規模態參數關係式，希望利用此關係式達到雙線耦合線設計三線耦合線的Balun。
另外透過寬邊耦合的機制，我們將覆背式共面波導與髮夾型共振器結合在一起，設計出插入損失從2.4 GHz到10.8 GHz皆大於-2 dB的帶通濾波器，並成功地在低頻創造額外的傳輸零點。而群速度在通帶的變化也介於0.18至0.6 ns，對超寬頻濾波器而言具有良好的線性度。

關鍵字

微帶線 ； 等角螺旋 ； 軸比頻寬 ； 正規模態參數

並列摘要

In this thesis, three topics are presented including the equiangular spiral antenna with planar microstrip line feed, ultra-wideband CBCPW broadside coupled band-pass filter, and wide band planar parallel-connected balun as well as the coupled-mode analysis. These planar microwave components are studied theoretically and experimentally.
First, the tapered microstrip-to-coplanar strip line feeding structure is incorporated into the equiangular spiral antenna to obtain broad impedance matching bandwidth and significant size reduction. The planar equiangular spiral antenna possesses 140% impedance bandwidth from 2.75 to 17 GHz, 132% axial ratio radiation bandwidth and an 3.5 dBi averaged antenna gain. This equiangular spiral antenna fed by microstrip
line is convenient to integrate with other microwave components.
Second, the UWB band-pass filter combining the CBCPW structure and the hairpin resonator possesses not only 2 dB insertion loss within the passband but also two transmission zeros located in the higher and lower frequency regions of the passband. The group delay within the passband varies between 0.18 and 0.6 ns, which represents that smooth group delay will avoid pulse signal dispersion in time domain.
Third, a wide-band balun is implemented by CPW structure. The unbalanced input impedance is 50 ohm and balance output impedance is 100 ohm. Bandwidth of back-to-back structure is larger than –0.7 dB from 100 MHz to 4 GHz. The size of the balun structure is only 8 mm*20 mm. Beside, normal mode parameter equations are used to investigate the three-line coupled structure.

並列關鍵字

microstrip line ； equiangular spiral ； axial ratio ； normal mode parameter

參考文獻

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