本論文提出三種新結構運用在直角差動傳輸線，補償內側線的電性長度，使差動傳輸線的內外路徑平衡，藉此降低直角差動傳輸線的差模到共模的模轉換雜訊。
我們使用電容補償的概念，提出了開路via的結構來抑制直角差動傳輸線的差模到共模之模轉換雜訊。首先，我們在直角差動傳輸線的訊號線使用開路via結構。相較於傳統直角差動傳輸線，從DC到10 GHz的頻域範圍之間，差模到共模之模轉換穿透雜訊，從-5.55 dB降低到-17.58 dB；時域的差模到共模的模轉換穿透電壓從0.053 V降低到0.008 V；差模穿透從-6.94 dB增加到-4.27 dB；電路長度為36 mm。為了縮小電路長度，我們在訊號線使用開路via結構以及縮窄線寬，同時做到電容和電感的補償，以達到阻抗匹配，可以將電路長度從36 mm縮小為18 mm。從DC到10 GHz的頻域範圍之間，差模到共模之模轉換穿透雜訊，稍微從-17.58 dB升高到-14.34 dB；時域的差模到共模的模轉換穿透電壓從0.008 V進一步降低到0.002 V；差模穿透從-4.27 dB進一步提升到-3.6 dB。
接著，為了增加開路via設計的自由度，以進一步縮小電路長度，我們提出在接地面使用開路via的直角差動傳輸線。相較於傳統直角差動傳輸線，從DC到10 GHz的頻域範圍之間，差模到共模之模轉換穿透雜訊，從-5.55 dB降低到-19.12 dB；時域的差模到共模的模轉換穿透電壓從0.053 V降低到-0.006 V；差模穿透從-6.94 dB降低到-3.48 dB；電路長度為33 mm。為了縮小電路長度，我們在接地面使用開路via結構以及縮窄線寬，同時做到電容和電感的補償，以達到阻抗匹配，可以將電路長度從33 mm縮小為9 mm。從DC到10 GHz的頻域範圍之間，差模到共模之模轉換穿透雜訊，稍微從-19.12 dB降低到-19.86 dB；時域的差模到共模的模轉換穿透電壓從-0.006 V進一步降低到-0.005 V；差模穿透從-3.48 dB進一步提升到-3.06 dB。
最後，為了不使用via以降低製作成本，我們使用電感補償的概念，提出了在接地面使用短槽線的結構，來抑制直角差動傳輸線的差模到共模之模轉換雜訊。相較於傳統直角差動傳輸線，從DC到10 GHz的頻域範圍之間，差模到共模的模轉換穿透雜訊，從原本的-5.55 dB，降低到-18.21 dB。時域的差模到共模的模轉換穿透電壓也從傳統的0.053 V，降低到-0.012 V。我們也將線寬增寬，優化其模轉換抑制效果。從DC到10 GHz的頻域範圍之間，在接地面使用線寬增寬及短槽線結構的差模到共模的模轉換穿透雜訊，從-18.21 dB進一步降低到-20.72 dB；時域的差模到共模的模轉換穿透電壓也從-0.012 V進一步降低到0.006 V。前述兩種短槽線結構的差模穿透訊號分別為-4.6 dB和-4.8 dB以上，皆大於傳統直角差動傳輸線的-6.94 dB。

This thesis proposes three new structures to balance the electrical lengths of the inner and outer lines of the right-angled differential transmission line. As a result, the differential-mode to common-mode noise conversion of the right-angled differential transmission line can be reduced.
We propose an open-circuited via structure to suppress the differential-mode to common-mode noise conversion of the right-angled differential transmission line. The open-circuited via structure utilizes the concept of capacitive compensation to achieve electrical length balancing between the inner and outer lines of the right-angled differential transmission line, thereby suppressing the noise conversion. First, we deploy the open-circuited via structure on the signal line of the right-angled differential transmission line. This newly proposed structure solely occupies space on the signal line, allowing for more flexibility in the ground plane layout. From DC to 10 GHz, as compared to traditional right-angled differential transmission line, the open-circuited via structure on the signal line significantly reduces the differential-mode to common-mode noise conversion from -5.55 dB to -17.58 dB. Additionally, the differential-mode to common-mode conversion transmission voltage in the time-domain is decreased from 0.053 V to 0.008 V. The differential-mode transmission coefficient is increased from -6.94 dB to -4.27 dB. The circuit length is 36 mm. To reduce the circuit length, we implement open-circuited via structure along with narrowed signal line. This approach simultaneously adopts the capacitive and inductive compensation to achieve impedance matching. As a result, the circuit length is significantly reduced from 36 mm to 18 mm. From DC to 10 GHz, as compared with the open-circuited via structure without narrowed signal line, the differential-mode to common-mode noise conversion is slightly increased from -17.58 dB to -14.34 dB. In addition, the differential-mode to common-mode conversion transmission voltage is further decreased from 0.008 V to 0.002 V, and the differential-mode transmission coefficient increased from -4.27 dB to -3.6 dB. Based on the above results, both the open-circuited via structure with and without the narrowed signal line exhibit excellent differential signal transmission performance.
To release the design flexibility and further reduce the circuit length, we deploy the open-circuited via structure on the ground plane of the right-angled differential transmission line. As compared to the open-circuited via on the signal line, the dimensions of the open-circuited via on the ground plane are not constrained by the signal line width. This allows for further miniaturization of the open-circuited via structure. From DC to 10 GHz, as compared to the traditional right-angled differential transmission line, the open-circuited via structure on the ground plane significantly reduces the differential-mode to common-mode noise conversion from -5.55 dB to -19.12 dB. The differential-mode to common-mode conversion transmission voltage in the time-domain is decreased from 0.053 V to -0.006 V, and the differential-mode transmission coefficient is increased from -6.94 dB to -3.48 dB. Additionally, the circuit length is 33 mm. To further reduce the circuit length, we employ open-circuited via structure on the ground plane along with narrowed signal line. The capacitive and inductive compensation are simultaneously adopted to achieve impedance matching. This allows for shrinking the circuit length from 33 mm to 9 mm, achieving a more compact circuit length. From DC to 10 GHz, as compared with the open-circuited via structure without narrowed signal line, the differential-mode to common-mode noise conversion is slightly decreased from -19.12 dB to -19.86 dB. The differential-mode to common-mode conversion transmission voltage in the time-domain is further decreased from -0.006 V to -0.005 V, and the differential-mode transmission coefficient is increased from -3.48 dB to -3.06 dB. Based on the above results, both the open-circuited via structure with and without the narrowed signal line exhibit excellent differential-mode signal transmission.
Finally, to eliminate the need for via and therefore reduce manufacturing costs, we propose a short-circuited slot on the ground plane to suppress the differential-mode to common-mode noise conversion in the right-angled differential transmission line. The short-circuited slot utilizes the inductive compensation to achieve equal electrical lengths between the inner and outer lines of the right-angled differential transmission line. It helps to suppress the conversion noise. From DC to 10 GHz, as compared to the traditional right-angled differential transmission line, the short-circuited slot structure on the ground plane significantly reduces the differential-mode to common-mode noise conversion from -5.55 dB to -18.21 dB. In addition, the differential-mode to common-mode conversion transmission voltage is decreased from 0.053 V to -0.012 V. By widening the signal line width, we further reduce differential-mode to common-mode noise conversion. From DC to 10 GHz, as compared with the short-circuited slot without widening signal line, the differential-mode to common-mode noise conversion is further reduced from -18.21 dB to -20.72 dB. Additionally, the time-domain differential-to-common mode transmission voltage is further reduced from -0.012 V to 0.006 V. The differential-mode transmission coefficients of the short-circuited slot with and without widening signal line are larger than -4.6 dB and -4.8 dB, respectively, which are higher than -6.94 dB of the traditional right-angled differential transmission line. Therefore, the short-circuited slot structure exhibits excellent differential-mode signal transmission performance.

[1] S. H. Hall, G. W. Hall, and J. A. McCall, High-Speed Digital System Design: A Handbook of Interconnect Theory and Design Practices. New York, NY, USA: Wiley, 2000
[2] P. E. Fornberg, M. Kanda, C. Lasek, M. Piket-May, and S. H. Hall, “The impact of a nonideal return path on differential signal integrity,” IEEE Trans. Electromagn. Compat., vol. 44, no. 1, pp. 11–15, Feb. 2002.
[3] Y. Massoud, J. Kawa, D. MacMillen, and J. White, “Modeling and analysis of differential signaling for minimizing inductive crosstalk,” Proc. Design Automation Conf., pp. 804-809, June 2001.
[4] G.-H. Shiue and R.-B. Wu, “Reduction in reflections and ground bounce for signal line over slotted power plane using differential coupled microstrip lines,” IEEE Trans. Adv. Packag., vol. 32, no. 3, pp. 581-588, Aug. 2009.
[5] S. -J. Wu, C. -H. Tsai, T. -L. Wu, and T. Itoh, “A novel wideband common-mode suppression filter for gigahertz differential signals using coupled patterned ground structure,” IEEE Trans. Microw. Theory Tech., vol. 57, no. 4, pp. 848-855, April 2009.
[6] J.-D. Cai, K.-C. Chen, and C.-L. Wang, “Mode conversion and common-mode noise reduction using periodic structure filter,” IEEE Trans. Electromagn. Compat., vol. 64, no. 4, pp. 1021-1030, Aug. 2022.
[7] G.-H. Shiue, C.-M. Hsu, C.-L. Yeh, and C.-F. Hsu, “A comprehensive investigation of a common-mode filter for gigahertz differential signals using quarter-wavelength resonators,” IEEE Trans. Compon. Packag. Manuf. Technol., vol. 4, no. 1, pp. 134-144, Jan. 2014.
[8] T. Adiprabowo, D.-B. Lin, Y.-H. Zheng, Y. H. Chen, C.-Y. Zhuang, and B.-H. Tsai, “Dual-band high absorbing and broadband suppressing common-mode noise filter,” IEEE Trans. Electromagn. Compat., vol. 64, no. 2, pp. 386-395, April 2022.
[9] H.-W. Liu, C.-H. Cheng, P.-J. Li, and T.-L. Wu, “A novel compact single-stage absorption common-mode filter,” IEEE Trans. Electromagn. Compat., vol. 64, no. 1, pp. 111-118, Feb. 2022.
[10] L.-S. Wu, J.-F. Mao, and W.-Y. Yin, “Slow-wave structure to suppress differential-to-common mode conversion for bend discontinuity of differential signaling,” IEEE Elect. Des. Adv. Packag. Syst. Symp. (EDAPS), Taipei, Taiwan, 2012.
[11] 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. Adv. Packag., vol. 29, no. 3, pp. 560-569, Aug. 2006.
[12] S. Lee, J. Lim, S. Oh, Y. Kim, D. Oh, and J. Lee, “Differential-to-common-mode conversion suppression using mushroom structure on bent differential transmission lines,” IEEE Trans. Compon. Packag. Manuf. Technol., vol. 9, no. 4, pp. 702-711, April 2019.
[13] B.-R. Huang, C.-H. Chang, R.-Y. Fang, and C.-L. Wang, “Bended differential transmission line using compensation inductance and capacitance,” 2015 IEEE 19th Workshop on Signal and Power Integrity (SPI), Berlin, Germany, 2015.
[14] B. J. Pierquet, T. C. Neugebauer, and D. J. Perreault, “Inductance compensation of multiple capacitors with application to common- and differential-mode filters,” IEEE Trans. Power Electron., vol. 21, no. 6, pp. 1815-1824, Nov. 2006.
[15] D.-B. Lin, C.-P. Huang, and H.-N. Ke, “Using stepped-impedance lines for common-mode noise reduction on bended coupled transmission lines,” IEEE Trans. Compon. Packag. Manuf. Technol., vol. 6, no. 5, pp. 757-766, May 2016.
[16] C. Gazda, D. V. Ginste, H. Rogier, R.-B. Wu, and D. D. Zutter, “A wideband common-mode suppression filter for bend discontinuities in differential signaling using tightly coupled microstrips,” IEEE Trans. Adv. Packag., vol. 33, no. 4, pp. 969-978, Nov. 2010.
[17] 顏子祥(2016)。降低換層差動傳輸線之共模與差模雜訊。國立台灣科技大學電子工程學系碩士論文，台北市。取自https://hdl.handle.net/11296/5f7nuq。
[18] R.-Y. Fang and C.-L. Wang, “Miniaturized coplanar waveguide to rectangular waveguide transition using inductance-compensated slotline,” IEEE Trans. Compon. Packag. Manuf. Technol., vol. 2, no. 10, pp. 1666-1671, Oct. 2012.