超寬頻平衡器與對數週期天線在印刷電路板上之整合設計

Integrated PCB Design of UWB Balun and Log-Periodic Antennas

吳翰揚(Han-Yang Wu)

指導教授 ： 林怡成

國立臺灣大學/電機資訊學院/電信工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.10335

摘要

對數週期偶極天線屬於非頻變天線的一種，具有線性極化與平穩的增益場型（Gain Pattern）等特性，非常適合應用在EMI或天線的量測上。傳統的對數週期偶極天線是由金屬圓柱所組成，並用同軸電纜來饋入，造成天線的體積及重量都較大，且難以製作等缺點。近年來，有文獻提出運用平面印刷電路板技術製作的對數週期偶極天線，然而，由於這些設計並未有效地遮蔽饋入線的輻射，以及並未運用平衡機制來饋入，其交叉極化的輻射量往往很高。在本論文中，我們運用印刷電路板技術，設計出兩款以平衡器（Balun）饋入之對數週期偶極天線。在前半部份，我們成功地在雙層印刷電路板上設計出一個頻寬為0.66~5.71GHz的平衡器，且其兩個輸出端之能量差在1.0dB以內，相位差則在10度以內。在後半部份，我們整合平衡器與對數週期偶極天線的設計，並同樣將之實現在雙層印刷電路板上。我們所提出的兩款天線設計，其頻寬分別為0.8~3.2GHz與0.8~6.0GHz，反射係數的模擬與量測結果非常吻合。此外，全頻段量測之同極化（Co-Pol.）正向增益介於0dBi至6dBi之間，表現非常平穩，交叉極化隔離度（Cross-Pol. Isolation）則約為20dB。

關鍵字

平衡器 ； 交叉極化隔離 ； 對數週期偶極天線 ； 平面化天線 ； 寬頻

並列摘要

The log-periodic dipole antenna (LPDA) is categorized as a frequency independent antenna with linear polarization and stable gain patterns; therefore it is suitable for the source antenna in EMI/Antenna measurement. Traditional LPDA is made of metal cylinders fed by coaxial cables making the antenna heavy and difficult to fabricate. Planar printed circuit board (PCB) LPDA was proposed recently; however, its unshielded and unbalanced feeding line may cause the cross-polarization too high to be used for practical applications. In this thesis, we propose a balun-based feeding scheme integrated with the planar LPDA using the multi-layered PCB technology. In the first half of the thesis, we design a Marchand balun in a multi-layered PCB with measured amplitude and phase balance within 1.0 dB and 10 degrees respectively over the 0.66~5.71 GHz band. In the second half of this thesis, we integrate the developed balun with the planar LPDA on the same PCB. Two designs are demonstrated for the 0.8~3.2 GHz and 0.8~6.0 GHz bands respectively. Both designs show good results in the wideband impedance matching, stable broadside gain range 0~6 dBi, and the highly isolated cross-polarization of 20 dB over the entire band.

並列關鍵字

Balun ； cross-polarization isolation ； LPDA, planar antenna ； broadband

參考文獻

[1] D. E. Isbell, “Log periodic dipole arrays”, IEEE Transactions on Antennas and Propagation, Vol. 8, No. 3, pp. 260 - 267, May. 1960.

[2] R. L. Carrel, “The design of log-periodic dipole antennas”, IRE International Convention Record, Vol. 9, Part 1, pp. 61 - 75, Mar. 1961.

[3] K. E. Jones, and P. E. Mayes, ”Continuously Scaled Transmission Lines with Applications to Log-Periodic Antennas”, IEEE Transactions on Antennas and Propagation, Vol. 17, No. 1, pp.2 – 9, Jan. 1969.

[4] C. C. Bantin, and K. G. Balmain, “Study of Compressed Log-Periodic Dipole Antennas”, IEEE Transactions on Antennas and Propagation, Vol. 18, No. 2, pp. 195 - 203, Mar. 1970.

[5] Z. L. Gong, and K. G. Balmain, “Reduction of the Anomalous Resonances of Symmetric Log-Periodic Dipole Antennas”, IEEE Transactions on Antennas and Propagation, Vol. 34, No. 12, pp.1404 – 1410, Dec. 1986.