跨槽信號線中電磁相容問題之模型化分析及電性設計

Abstract

本文針對跨槽信號線引發的電磁相容問題，提出相關的解決方案及模型化方法。本文中提出的等效電路，將物理結構以傳輸線模型作為基礎，與其電氣特性建立良好的連結。基於所提出的模型架構，本文提出三種低成本的解決方案分別解決當高速信號線跨越蝕刻溝槽的參考平面時，所誘發之串音、共模輻射及材料損耗所造成的信號失真等問題。 本文首先探討信號線間透過槽線的耦合，所誘發之串音問題。針對此問題，本文提出了一低成本解決方案，透過開路之微帶線與槽線之並聯銜接，可有效地降低因符際干擾所造成之串音。透過模擬及實驗的結果，本文驗證了針對低及高頻率之傳輸速度的設計方法。 其次，針對高速共模雜訊，因激發開槽線所產生之共模輻射議題，本文提出一種接地式共振腔技術，用以降低高頻的共模幅射及模態轉換。透過巧妙的將開路式的微帶線與槽線以並聯形式相連，所形成之接地式共振腔可有效的控制共模傳輸特性，以避免激發類似天線般的槽線。在一實驗實例中，以此低成本結構在2.29到3.48 GHz頻率範圍內，有效降低遠場輻射的電場大小。同時，此電場抑制的頻寬如同所提出結構的共模傳輸頻寬。 最後，本文提出一新穎架構，除具備差模信號等化器的功能外，亦擁有寬頻的共模雜訊抑制。就目前的文獻探討，可知此架構為首次在學術界中被提出，同時具備上述的兩種功能。透過妥善設計耦合槽線及末端之電阻值，將其與差模信號線在接收端附近以並聯方式銜接，此電阻不但可提供差模信號的等化功能，亦可吸收部分的共模雜訊。差模信號的傳輸品質經一實驗實例的量測驗證，在信號傳輸速度為8 Gbps時，相較於未設計等化器結構的情況，可明顯改善接收之眼圖。

The dissertation provides solutions and modeling methods for electromagnetic compatibility problems caused by slot-crossing signal traces. Based on the transmission line models, equivalent circuit models for the signal traces were created, which transformed physical configurations into electrical behavior. With the help of the constructed models, low-cost solutions have been proposed to solve the unwanted crosstalk, common-mode radiation and lossy material problems when high-speed signals cross slotted reference plane. In the beginning, the crosstalk between signal traces crossing the same slot is first investigated. By connecting an open-circuited microstrip line in parallel with the slotline between the crossing signal lines, a branched reflector technique is proposed to suppress the crosstalk due to the inter-symbol interference. The design methods both for low- and high-frequency transmission have been proposed and validated by the simulation and experimental results. Second, a grounded resonator technique is designed to reduce common-mode radiation and mode conversion, which are resulted from common-mode noise striding across the slotted plane. By properly linking the open-circuited transmission lines with the slotline, the common-mode transmission can be controlled to prevent excitation of antenna-like slotline. This low-cost solution makes the radiated electric field to be effectively decreased from 2.29 to 3.48 GHz, which is consistent to the designed passband. Finally, a differential-mode equalizer with broadband common-mode suppression is proposed. To the best knowledge of the author, these dual functions are the first time to be integrated in a single structure. Through suitably connecting the coupled slotlines with the differential line structure, the terminated resistors at the end of coupled slotlines provide the equalization and absorption for differential-mode transmission and common-mode noise, respectively. With the experimental validation, the eye-diagram of differential-mode transmission at 8 Gbps has been greatly improved comparing that without the designed configuration.