抑制共模態之人工耦合傳輸線及其應用

利用傳輸線超材料的概念，本文提出具有寬頻共模態抑制的耦合傳輸線。此傳輸線由一對耦合線及蕈狀接地結構所組成，其等效電路結構能有效解釋其傳輸特性。根據奇偶模態分析，在奇模態激發時，此耦合線呈現電磁波在準TEM傳輸線傳播的特性，但在共模態激發時，卻產生寬頻的抑制帶。利用此背接蕈狀結構之耦合線的特點，本文實現寬頻且微小的共模濾波器和平衡非平衡轉換器，有別於傳統使用鐵磁性材料的方式，兩者皆可以低溫共燒陶瓷基板或是綠能材料實現。共模濾波器僅使用四個單元合成，大小只有0.16 훌g × 0.26 훌g，其對應的物理大小為3.2 mm × 5.12 mm，此結構可以對3.8秭赫茲到7.1 秭赫茲的共模雜訊產生超過10 dB的抑制，並在時域有50%的共模電壓抑制，且對於差模，到十秭赫茲皆維持很好的傳輸。利用此單元耦合線，本文設計出擁有兩個零點的單元等效電路，達到寬頻且微小化貼片式共模濾波器設計。至於平衡非平衡轉換器，本文使用虛部阻抗的概念去設計此寬頻轉換器，除了在3.3秭赫茲到7.1秭赫茲之內幅度偏差維持在0.3 dB以下外，其相位偏差亦能維持在3度之內。評估轉換器好壞的共模雜訊抑制比率在3.3秭赫茲到7.1秭赫茲寬頻的區域能超過30 dB，且其面積大小只有0.063 × 0.44 λg2，物理大小只有1.6 × 11.2 mm2。利用此背接蕈狀結構之耦合線，本文更進一步提出任意阻抗轉換之超微小轉換器，此轉換器具有40 %的比例頻寬且電性大小只有0.088 λg × 0.078 λg。

關鍵字

低溫共燒陶瓷；耦合線；共模扼流線圈；共模雜訊；平衡非平衡轉換器；系統封裝層級

並列摘要

An artificial coupled-line with broadband even-mode rejection is proposed based on the concept of transmission line metamaterial. It is composed of a pair of coupled lines and a ground plane backed by mushroom structures and called mushroom-backed coupled-line (MBCL). Its equivalent circuit model is established to explain wave propagation property. Based on odd and even mode analyses, the proposed coupled-line behaves like a quasi-TEM transmission line for odd-mode excitation while it possesses a wide stopband for even-mode excitation. Based on the proposed MBCL, a common mode filter and a passive balun are designed with a compact size and broadband operation. Both structures are realized on the LTCC technology. For the common-mode filter with four unit cells, its size is 0.16 훌g × 0.26 훌g corresponding to a real size of 3.2 mm × 5.12 mm. The filter shows over 10 dB reduction for common-mode noise from 3.8 GHz to 7.1 GHz in frequency domain and over 50% suppression for voltage amplitude in time domain. Moreover, a common-mode filter is designed based on a unit-cell equivalent circuit model with two transmission zeros for common mode. The structure is compact and can be designed for surface mounted devices. As for the broadband balun, a new concept is presented to design it. The realized balun exhibits good amplitude imbalance of less than 0.3 dB and phase imbalance of 179 ± 3°with the return loss greater than 10 dB from 3.3 to 7.1 GHz. Its electrical size is only 0.063 × 0.44 λg2. Furthermore, a compact balun with a fractional bandwidth of 40 % is realized. It can be designed for arbitrary real impedance transformation ratio and its electrical size is only 0.088 λg × 0.078 λg.

並列關鍵字

Low temperature co-fired ceramic (LTCC) ； Coupled-line ； Common mode choke ； Common-mode noise ； Balun ； System-in-Package (SiP)

參考文獻

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[2] J. L. Knighten, N. W. Smith, J. T. DiBene, L. O. Hoeft, “EMI common-mode current dependence on delay skew imbalance in high speed differential transmission lines operating at 1 gigabit/second data rates,” in Proc. IEEE Int. Symp. Quality Electronic Design., CA, Mar. 2000, pp. 309-313.

[3] G. H. Shiue, W. D. Guo, C. M. Lin, and R. B. Wu, “Noise Reduction Using Compensation Capacitance for Bend Discontinuities of Differential Transmission Lines,” IEEE Trans. on Adv. Packag., vol. 29, no. 3, p.p. 560-569 ,Aug. 2006

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[5] I. I. Ao Ieong, C. H. Tsai, and T. L. Wu, “An ultra-compact common-mode filter for RF interference control in 3G wireless communication systems,” in Proc. IEEE Int. Symp. Trans. Electromagn. Compat., Fort Lauderdale, Florida, July 2010.

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抑制共模態之人工耦合傳輸線及其應用

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